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    BMW Cars 1999-06

    Cylinder Head 1

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    There are two basic types of cylinder heads used on BMW 3 Series automobiles: the Single Overhead Camshaft (SOHC) and the Dual Overhead Camshaft (DOHC) cylinder heads.

    These cylinder heads are made of an aluminum alloy due to its light weight, durability and heat transfer qualities. Whether made from aluminum or iron, all cylinder heads have valves and seats. Some use two valves per cylinder, while the more hi-tech engines will utilize a multi-valve configuration using 3, 4 and even 5 valves per cylinder. When the valve contacts the seat, it does so on precision machined surfaces, which seals the combustion chamber. All cylinder heads have a valve guide for each valve. The guide centers the valve to the seat and allows it to move up and down within it. The clearance between the valve and guide can be critical. Too much clearance and the engine may consume oil, lose vacuum and/or damage the seat. Too little, and the valve can stick in the guide causing the engine to run poorly if at all, and possibly causing severe damage. The last component all cylinder heads have are valve springs. The spring holds the valve against its seat. It also returns the valve to this position when the valve has been opened by the valve train or camshaft. The spring is fastened to the valve by a retainer and valve locks (sometimes called keepers). Aluminum heads will also have a valve spring shim to keep the spring from wearing away the aluminum.

    An ideal method of rebuilding the cylinder head would involve replacing all of the valves, guides, seats, springs, etc. with new ones. However, depending on how the engine was maintained, often this is not necessary. A major cause of valve, guide and seat wear is an improperly tuned engine. An engine that is running too rich, will often wash the lubricating oil out of the guide with gasoline, causing it to wear rapidly. Conversely, an engine which is running too lean will place higher combustion temperatures on the valves and seats allowing them to wear or even burn. Springs fall victim to the driving habits of the individual. A driver who often runs the engine rpm to the redline will wear out or break the springs faster then one that stays well below it. Unfortunately, mileage takes it toll on all of the parts. Generally, the valves, guides, springs and seats in a cylinder head can be machined and re-used, saving you money. However, if a valve is burnt, it may be wise to replace all of the valves, since they were all operating in the same environment. The same goes for any other component on the cylinder head. Think of it as an insurance policy against future problems related to that component.

    Unfortunately, the only way to find out which components need replacing, is to disassemble and carefully check each piece. After the cylinder head(s) are disassembled, thoroughly clean all of the components.

    Cylinder Head Overhaul



    Assembly

    The first step for any assembly job is to have a clean area in which to work. Next, thoroughly clean all of the parts and components that are to be assembled. Finally, place all of the components onto a suitable work space and, if necessary, arrange the parts to their respective positions.

    OHC Engines
    Cup Type Camshaft Followers

    To install the springs, retainers and valve locks on heads which have these components recessed into the camshaft follower's bore, you will need a small screwdriver-type tool, some clean white grease and a lot of patience. You will also need the C-clamp style spring compressor and the OHC tool used to disassemble the head.

    1. Lightly lubricate the valve stems and insert all of the valves into the cylinder head. If possible, maintain their original locations.
    2.  
    3. If equipped, install any valve spring shims which were removed.
    4.  
    5. If equipped, install the new valve seals, keeping the following in mind:

      If the valve seal presses over the guide, lightly lubricate the outer guide surfaces.
       
      If the seal is an O-ring type, it is installed just after compressing the spring but before the valve locks.
       

    6.  
    7. Place the valve spring and retainer over the stem.
    8.  
    9. Position the spring compressor and the OHC tool, then compress the spring.
    10.  
    11. Using a small screwdriver as a spatula, fill the valve stem side of the lock with white grease. Use the excess grease on the screwdriver to fasten the lock to the driver.
    12.  
    13. Carefully install the valve lock, which is stuck to the end of the screwdriver, to the valve stem then press on it with the screwdriver until the grease squeezes out. The valve lock should now be stuck to the stem.
    14.  
    15. Repeat Steps 6 and 7 for the remaining valve lock.
    16.  
    17. Relieve the spring pressure slowly and insure that neither valve lock becomes dislodged by the retainer.
    18.  
    19. Remove the spring compressor tool.
    20.  
    21. Repeat Steps 2 through 10 until all of the springs have been installed.
    22.  
    23. Install the followers, camshaft(s) and any other components that were removed for disassembly.
    24.  



    Click image to see an enlarged view

    Fig. Once assembled, check the valve clearance and correct as needed

    SOHC Cylinder Heads With Rocker Arms
    1. Lightly lubricate the valve stems and insert all of the valves into the cylinder head. If possible, maintain their original locations.
    2.  
    3. If equipped, install any valve spring shims which were removed.
    4.  
    5. If equipped, install the new valve seals, keeping the following in mind:

      If the valve seal presses over the guide, lightly lubricate the outer guide surfaces.
       
      If the seal is an O-ring type, it is installed just after compressing the spring but before the valve locks.
       

    6.  
    7. Place the valve spring and retainer over the stem.
    8.  
    9. Position the spring compressor tool and compress the spring.
    10.  
    11. Assemble the valve locks to the stem.
    12.  
    13. Relieve the spring pressure slowly and insure that neither valve lock becomes dislodged by the retainer.
    14.  
    15. Remove the spring compressor tool.
    16.  
    17. Repeat Steps 2 through 8 until all of the springs have been installed.
    18.  
    19. Install the camshaft(s), rockers, shafts and any other components that were removed for disassembly.
    20.  

    Disassembly
    OHC Heads

    Whether it is a single or dual overhead camshaft cylinder head, the disassembly procedure is relatively unchanged. One aspect to pay attention to is careful labeling of the parts on the dual camshaft cylinder head. There will be an intake camshaft and followers as well as an exhaust camshaft and followers and they must be labeled as such. In some cases, the components are identical and could easily be installed incorrectly. DO NOT MIX THEM UP! Determining which is which is very simple; the intake camshaft and components are on the same side of the head as was the intake manifold. Conversely, the exhaust camshaft and components are on the same side of the head as was the exhaust manifold.



    Click image to see an enlarged view

    Fig. Exploded view of a valve, seal, spring, retainer and locks from an OHC cylinder head



    Click image to see an enlarged view

    Fig. Example of a multi-valve cylinder head. Note how it has 2 intake and 2 exhaust valve ports



    Click image to see an enlarged view

    Fig. Keep the cylinder head parts organized. Any reinstalled component must be installed from where it was removed as they develop wear patterns over time, or have been machined with the cylinder head during manufacturing

    Cup Type Camshaft Followers

    Most cylinder heads with cup type camshaft followers will have the valve spring, retainer and locks recessed within the follower's bore. You will need a C-clamp style valve spring compressor tool, an OHC spring removal tool (or equivalent) and a small magnet to disassemble the head.



    Click image to see an enlarged view

    Fig. C-clamp type spring compressor and an OHC spring removal tool (center) for cup type followers

    1. If not already removed, remove the camshaft(s) and/or followers. Mark their positions for assembly.
    2.  



    Click image to see an enlarged view

    Fig. Most cup type follower cylinder heads retain the camshaft using bolt-on bearing caps

    1. Position the cylinder head to allow use of a C-clamp style valve spring compressor tool.
    2.  


    NOTE
    It is preferred to position the cylinder head gasket surface facing you with the valve springs facing the opposite direction and the head laying horizontal.



    Click image to see an enlarged view

    Fig. Position the OHC spring tool in the follower bore, then compress the spring with a C-clamp type tool

    1. With the OHC spring removal adapter tool positioned inside of the follower bore, compress the valve spring using the C-clamp style valve spring compressor.
    2.  
    3. Remove the valve locks. A small magnetic tool or screwdriver will aid in removal.
    4.  
    5. Release the compressor tool and remove the spring assembly.
    6.  
    7. Withdraw the valve from the cylinder head.
    8.  
    9. If equipped, remove the valve seal.
    10.  


    NOTE
    Special valve seal removal tools are available. Regular or needle-nose type pliers, if used with care, will work just as well. If using ordinary pliers, be sure not to damage the follower bore. The follower and its bore are machined to close tolerances and any damage to the bore will effect this relationship.

    1. If equipped, remove the valve spring shim. A small magnetic tool or screwdriver will aid in removal.
    2.  
    3. Repeat Steps 3 through 8 until all of the valves have been removed.
    4.  

    Rocker Arm Type Camshaft Followers

    Most cylinder heads with rocker arm-type camshaft followers are easily disassembled using a standard valve spring compressor. However, certain models may not have enough open space around the spring for the standard tool and may require you to use a C-clamp style compressor tool instead.



    Click image to see an enlarged view

    Fig. Example of the shaft mounted rocker arms on some OHC heads



    Click image to see an enlarged view

    Fig. Another example of the rocker arm type OHC head. This model uses a follower under the camshaft

    1. If not already removed, remove the rocker arms and/or shafts and the camshaft. If applicable, also remove the hydraulic lash adjusters. Mark their positions for assembly.
    2.  



    Click image to see an enlarged view

    Fig. Before the camshaft can be removed, all of the followers must first be removed . . .



    Click image to see an enlarged view

    Fig. . . . then the camshaft can be removed by sliding it out (shown), or unbolting a bearing cap (not shown)

    1. Position the cylinder head to allow access to the valve spring.
    2.  
    3. Use a valve spring compressor tool to relieve the spring tension from the retainer.
    4.  



    Click image to see an enlarged view

    Fig. Compress the valve spring . . .


    NOTE
    Due to engine varnish, the retainer may stick to the valve locks. A gentle tap with a hammer may help to break it loose.



    Click image to see an enlarged view

    Fig. . . . then remove the valve locks from the valve stem and spring retainer

    1. Remove the valve locks from the valve tip and/or retainer. A small magnet may help in removing the small locks.
    2.  
    3. Lift the valve spring, tool and all, off of the valve stem.
    4.  



    Click image to see an enlarged view

    Fig. Remove the valve spring and retainer from the cylinder head

    1. If equipped, remove the valve seal. If the seal is difficult to remove with the valve in place, try removing the valve first, then the seal. Follow the steps below for valve removal.
    2.  



    Click image to see an enlarged view

    Fig. Remove the valve seal from the guide. Some gentle prying or pliers may help to remove stubborn ones

    1. Position the head to allow access for withdrawing the valve.
    2.  


    NOTE
    Cylinder heads that have seen a lot of miles and/or abuse may have mushroomed the valve lock grove and/or tip, causing difficulty in removal of the valve. If this has happened, use a metal file to carefully remove the high spots around the lock grooves and/or tip. Only file it enough to allow removal.

    1. Remove the valve from the cylinder head.
    2.  



    Click image to see an enlarged view

    Fig. All aluminum and some cast iron heads will have these valve spring shims. Remove all of them as well

    1. If equipped, remove the valve spring shim. A small magnetic tool or screwdriver will aid in removal.
    2.  
    3. Repeat Steps 3 though 9 until all of the valves have been removed.
    4.  

    Inspection

    Now that all of the cylinder head components are clean, it's time to inspect them for wear and/or damage. To accurately inspect them, you will need some specialized tools:



    A 0-1 in. micrometer for the valves
     
    A dial indicator or inside diameter gauge for the valve guides
     
    A spring pressure test gauge
     

    If you do not have access to the proper tools, you may want to bring the components to a shop that does.



    Click image to see an enlarged view

    Fig. Precision measuring tools for a thorough inspection include precision caliper, a micrometer, a dial indicator and a set of hole gauges

    There are several things to check on the cylinder head: valve guides, seats, cylinder head surface flatness, cracks and physical damage.

    Cracks And Physical Damage

    Generally, cracks are limited to the combustion chamber, however, it is not uncommon for the head to crack in a spark plug hole, port, outside of the head or in the valve spring/rocker arm area. The first area to inspect is always the hottest: the exhaust seat/port area.

    A visual inspection should be performed, but just because you don't see a crack does not mean it is not there. Some more reliable methods for inspecting for cracks include Magnaflux®, a magnetic process or Zyglo®, a dye penetrant. Magnaflux® is used only on ferrous metal (cast iron) heads. Zyglo® uses a spray on fluorescent mixture along with a black light to reveal the cracks. It is strongly recommended to have your cylinder head checked professionally for cracks, especially if the engine was known to have overheated and/or leaked or consumed coolant. Contact a local shop for availability and pricing of these services.

    Physical damage is usually very evident. For example, a broken mounting ear from dropping the head or a bent or broken stud and/or bolt. All of these defects should be fixed or, if unrepairable, the head should be replaced.

    Cylinder Head Flatness

    After you have cleaned the gasket surface of the cylinder head of any old gasket material, check the head for flatness.



    Click image to see an enlarged view

    Fig. Check the head for flatness across the center of the head surface using a straightedge and feeler gauge



    Click image to see an enlarged view

    Fig. Checks should also be made along both diagonals of the head surface

    Place a straightedge across the gasket surface. Using feeler gauges, determine the clearance at the center of the straightedge and across the cylinder head at several points. Check along the centerline and diagonally on the head surface. If the warpage exceeds 0.003 in. (0.076mm) within a 6.0 in. (15.2cm) span, or 0.006 in. (0.152mm) over the total length of the head, the cylinder head must be resurfaced. After resurfacing the heads of a V-type engine, the intake manifold flange surface should be checked, and if necessary, milled proportionally to allow for the change in its mounting position.

    Certain cracks can be repaired in both cast iron and aluminum heads. For cast iron, a tapered threaded insert is installed along the length of the crack. Aluminum can also use the tapered inserts, however welding is the preferred method. Some physical damage can be repaired through brazing or welding. Contact a machine shop to get expert advice for your particular dilemma.

    Valve Seats

    A visual inspection of the valve seats should show a slightly worn and pitted surface where the valve face contacts the seat. Inspect the seat carefully for severe pitting or cracks. Also, a seat that is badly worn will be recessed into the cylinder head. A severely worn or recessed seat may need to be replaced. All cracked seats must be replaced. A seat concentricity gauge, if available, should be used to check the seat run-out. If run-out exceeds specifications the seat must be machined (if no specification is given use 0.002 in. or 0.051mm).



    Click image to see an enlarged view

    Fig. The valve seat has 3 angles, 30°,45°, and 60°. The width of the 45° angle is measured with a precision caliper

    Refinishing & Repairing

    Many of the procedures given for refinishing and repairing the cylinder head components must be performed by a machine shop. Certain steps, if the inspected part is not worn, can be performed yourself inexpensively. However, you spent a lot of time and effort so far, why risk trying to save a couple bucks if you might have to do it all over again-

    Cylinder Head

    Most refinishing procedures dealing with the cylinder head must be performed by a machine shop. Read the sections below and review your inspection data to determine whether or not machining is necessary.

    Cylinder Head Surface

    If the cylinder head is warped, it must be machined flat. If the warpage is extremely severe, the head may need to be replaced. In some instances, it may be possible to straighten a warped head enough to allow machining. In either case, contact a professional machine shop for service.


    NOTE
    Any OHC cylinder head that shows excessive warpage should have the camshaft bearing journals align bored after the cylinder head has been resurfaced.


    WARNING
    Failure to align bore the camshaft bearing journals could result in severe engine damage including but not limited to: valve and piston damage, connecting rod damage, camshaft and/or crankshaft breakage.

    Valve Guides

    NOTE
    If any machining or replacements are made to the valve guides, the seats must be machined.

    Unless the valve guides need machining or replacing, the only service to perform is to thoroughly clean them of any dirt or oil residue.

    There are only two types of valve guides used on automobile engines: the replaceable-type (all aluminum heads) and the cast-in integral-type (most cast iron heads). There are four recommended methods for repairing worn guides.



    Knurling
     
    Inserts
     
    Reaming oversize
     
    Replacing
     

    Knurling is a process in which metal is displaced and raised, thereby reducing clearance, giving a true center, and providing oil control. It is the least expensive way of repairing the valve guides. However, it is not necessarily the best, and in some cases, a knurled valve guide will not stand up for more than a short time. It requires a special knurlizer and precision reaming tools to obtain proper clearances. It would not be cost effective to purchase these tools, unless you plan on rebuilding several of the same cylinder head.

    Installing a guide insert involves machining the guide to accept a bronze insert. One style is the coil-type which is installed into a threaded guide. Another is the thin-walled insert where the guide is reamed oversize to accept a split-sleeve insert. After the insert is installed, a special tool is then run through the guide to expand the insert, locking it to the guide. The insert is then reamed to the standard size for proper valve clearance.

    Reaming for oversize valves restores normal clearances and provides a true valve seat. Most cast-in type guides can be reamed to accept an valve with an oversize stem. The cost factor for this can become quite high as you will need to purchase the reamer and new, oversize stem valves for all guides which were reamed. Oversizes are generally 0.003 to 0.030 in. (0.076 to 0.762mm), with 0.015 in. (0.381mm) being the most common.

    To replace cast-in type valve guides, they must be drilled out, then reamed to accept replacement guides. This must be done on a fixture which will allow centering and leveling off of the original valve seat or guide, otherwise a serious guide-to-seat misalignment may occur making it impossible to properly machine the seat.

    Replaceable-type guides are pressed into the cylinder head. A hammer and a stepped drift or punch may be used to install and remove the guides. Before removing the guides, measure the protrusion on the spring side of the head and record it for installation. Use the stepped drift to hammer out the old guide from the combustion chamber side of the head. When installing, determine whether or not the guide also seals a water jacket in the head, and if it does, use the recommended sealing agent. If there is no water jacket, grease the valve guide and its bore. Use the stepped drift, and hammer the new guide into the cylinder head from the spring side of the cylinder head. A stack of washers the same thickness as the measured protrusion may help the installation process.

    Valve Seats

    NOTE
    Before any valve seat machining can be performed, the guides must be within factory recommended specifications.


    NOTE
    If any machining or replacements were made to the valve guides, the seats must be machined.

    If the seats are in good condition, the valves can be lapped to the seats, and the cylinder head assembled. See the valves section for instructions on lapping.

    If the valve seats are worn, cracked or damaged, they must be serviced by a machine shop. The valve seat must be perfectly centered to the valve guide, which requires very accurate machining.

    Springs, Retainers & Valve Locks

    There is no repair or refinishing possible with the springs, retainers and valve locks. If they are found to be worn or defective, they must be replaced with new (or known good) parts.

    Valves

    Any valves that were not replaced should be refaced and the tips ground flat. Unless you have access to a valve grinding machine, this should be done by a machine shop. If the valves are in extremely good condition, as well as the valve seats and guides, they may be lapped in without performing machine work.

    It is a recommended practice to lap the valves even after machine work has been performed and/or new valves have been purchased. This insures a positive seal between the valve and seat.


    WARNING
    Valves containing sodium cannot be resurfaced!

    Lapping The Valves

    NOTE
    Before lapping the valves to the seats, read the rest of the cylinder head section to insure that any related parts are in acceptable enough condition to continue.


    NOTE
    Before any valve seat machining and/or lapping can be performed, the guides must be within factory recommended specifications.

    1. Invert the cylinder head.
    2.  
    3. Lightly lubricate the valve stems and insert them into the cylinder head in their numbered order.
    4.  
    5. Raise the valve from the seat and apply a small amount of fine lapping compound to the seat.
    6.  
    7. Moisten the suction head of a hand-lapping tool and attach it to the head of the valve.
    8.  
    9. Rotate the tool between the palms of both hands, changing the position of the valve on the valve seat and lifting the tool often to prevent grooving.
    10.  
    11. Lap the valve until a smooth, polished circle is evident on the valve and seat.
    12.  
    13. Remove the tool and the valve. Wipe away all traces of the grinding compound and store the valve to maintain its lapped location.
    14.  


    WARNING
    Do not get the valves out of order after they have been lapped. They must be put back with the same valve seat with which they were lapped.

    Removal & Installation



    The components of the cylinder head and the mating surface of the cylinder head and engine block are machined within very precise tolerances. The components must be thoroughly cleaned, inspected and if necessary properly lubricated upon installation. Refer to the Engine Reconditioning information in this section for additional information.


    WARNING
    A camshaft removal tool should be used when removing the camshafts from the M42 engine and all E36 6-cylinder engines. Failure to use the proper tool or its equivalent could result in camshaft breakage.


    NOTE
    Both a camshaft and a crankshaft alignment tool are necessary when reinstalling the camshafts onto the cylinder head of BMW M42 engines and all E36 model engines.


    WARNING
    The cylinder head bolts used on E36 6-cylinder engines with a cast iron block are a different length and torque specification than those used on E36 6-cylinder engines with a cast aluminum block and must not be interchanged!

    E36 6-Cylinder Engines
    1. Properly relieve the fuel system pressure.
    2.  
    3. Disconnect the negative battery cable.
    4.  
    5. Before proceeding with the cylinder head removal be sure the engine has cooled sufficiently.
    6.  
    7. Raise and safely support the vehicle.
    8.  
    9. Remove the lower engine splash shield.
    10.  
    11. Disconnect the exhaust manifolds from the exhaust pipes.
    12.  
    13. Drain the engine coolant from the radiator and the engine block into a sealable container. The engine block drain plug is located on the right side of the block near the rear exhaust manifold, just below the exhaust ports for cylinder numbers four and five.
    14.  
    15. Remove the rear hood seal, then remove the fasteners securing the sealed plastic housing for the engine wiring harness from the passenger compartment fresh air intake shroud.
    16.  
    17. Remove the fasteners securing the fresh air intake shroud to the fire wall, and remove the shroud.
    18.  
    19. If equipped, remove the plastic trim covers from the top of the engine.
    20.  
    21. Disconnect the Mass Air Flow (MAF) sensor and remove intake manifold air duct along with the air filter housing assembly.
    22.  
    23. Remove the throttle cable from the throttle body linkage, disconnect the coolant hoses, the Throttle Position (TP) sensor electrical connector, the throttle body mounting fasteners, and remove the throttle body assembly. Cover the opening of the intake manifold to prevent any debris from entering.
    24.  
    25. Remove the intake manifold support bracket fasteners from the intake manifold and loosen the support bracket fasteners on the engine block.
    26.  
    27. Disconnect the fuel feed and return lines and make note of their location for reassembly.
    28.  
    29. Disconnect the vacuum hoses from the intake manifold, and loosen the clamps for the idle speed stabilizer underneath the manifold, and disconnect the hoses.
    30.  
    31. Remove the intake manifold intake port fasteners and carefully lift the manifold away from the engine. Cover the intake ports to ensure that no debris enters the ports.
    32.  
    33. Remove the ground cable at the front of the cylinder head, then remove the two radiator hoses from the thermostat housing, and remove the housing.
    34.  
    35. Remove the exhaust manifolds.
    36.  
    37. Remove the wire connectors for the ignition coils and cylinder head sensors and remove the coils, then remove the cylinder head cover.
    38.  
    39. Rotate the engine in the direction of rotation to Top Dead Center (TDC) for cylinder number one. Cylinder number one will be at TDC when the intake and exhaust camshaft peaks for cylinder number one face each other
    40.  
    41. Lock the engine in the TDC position by placing the crankshaft alignment tool No. 11 2 300 through the machined hole in the engine block, just below the starter motor located on the left lower portion of the engine block. Slide the alignment tool through the machined hole in the block and into the machined hole in the flywheel to prevent movement of the crankshaft.
    42.  
    43. The camshafts are held in the TDC position by placing tool No. 11 3 240 or equivalent on the valve cover mating surface at the back of the cylinder head and onto the squared ends of the camshafts, securing the camshafts such that two sides of the squared ends are parallel with the cam cover gasket mating surface. With the camshafts in this position, the arrows on the sprockets will be facing up.
    44.  
    45. Remove the valve cover mounting studs.
    46.  
    47. Remove the two hex plugs at the front of the cylinder head to access the exhaust camshaft sprocket mounting bolts, then loosen the exhaust cam sprocket bolts two turns.
    48.  
    49. Press down on the secondary cam chain tensioner between the two camshaft sprockets and install tool No. 11-3-292 or equivalent through the back side of the tensioner housing to hold the tensioner down. A similar sized and suitably hardened drill bit can be substituted for tool No. 11 3 292.
    50.  
    51. If equipped with the hydraulic variable camshaft control system (VANOS)
      1. Remove the fasteners from the front of the cylinder head securing VANOS unit to the cylinder head.
      2.  
      3. Disconnect the hydraulic lines and sensor connectors from the VANOS unit.
      4.  
      5. On VANOS equipped engines with a spring plate installed on the intake camshaft, place sprocket tool No. 11 5 490 or equivalent onto the exhaust camshaft sprocket and carefully rotate the sprocket clockwise to allow the helical gear of the VANOS unit to be released from the intake camshaft and to allow the VANOS unit to be pulled away from the front of the cylinder head. On models without a spring plate, the VANOS unit can be removed without the use of the special tool.
      6.  
      7. If tool No. 11 5 490 or equivalent is not available, move the camshaft sprockets to release the VANOS by using a suitable drift and soft faced mallet and lightly tapping on a sprocket tooth of the intake cam sprocket to rotate both cam sprockets clockwise, while alternately pulling on the VANOS unit to release it. This procedure may need to be repeated several times to fully release the VANOS unit, and must be performed very carefully, in such a manner to not distort or damage the teeth of the cam sprocket.
      8.  

    52.  
    53. Remove the intake and exhaust camshaft sprockets, the hydraulic cam chain tensioner, and the cam chain guide.
    54.  
    55. From the side of the right front area of the engine, remove the cap nut for the cam chain tensioner for the cam chain that runs between the crankshaft and the exhaust camshaft sprocket. Use care when removing the tensioner cap nut as the cam tensioner spring applies pressure to the cap nut.
    56.  
    57. Remove the exhaust cam tensioner, and then release the sprocket from the cam chain.
    58.  
    59. Attach a wire tie or mechanic's wire to the cam chain and temporarily secure the chain fully extended.
    60.  
    61. Remove the crankshaft alignment tool from the engine and flywheel locking the engine in the TDC position.
    62.  
    63. While holding the crankshaft to exhaust camshaft cam chain, rotate the engine 30° counterclockwise to avoid damaging the valves during cylinder head removal and reinstallation.
    64.  
    65. With the attached wire tie or mechanic's wire secured to the cam chain, carefully lower the chain downward making sure there is enough exposed wire to retrieve the chain for reinstallation.
    66.  
    67. Remove the fasteners located in a recessed area near the front of the camshafts securing the front of the cylinder head to the engine block.
    68.  
    69. In the reverse order of the tightening sequence, using a proper sized Torx® bit or tool No. 11 2 250, loosen the cylinder head mounting bolts in three steps as follows:

      Step 1: 90°
       
      Step 2: 90°
       
      Step 3: Completely remove the bolt
       

    70.  
    71. With all of the cylinder head bolts removed, verify that all electrical connectors and fluid lines have been removed and lift the cylinder head off the engine block.
    72.  


    NOTE
    It is not recommended to machine the cylinder head surface of the S52 engine. If machining the cylinder head of an M52 engine, a 0.012 inch (0.3mm) thicker head gasket is available for reassembly.



    Click image to see an enlarged view

    Fig. Cylinder head mounting bolt tightening sequence-E36 models with 6-cylinder engines

    To install:

    1. Thoroughly clean the deck surface of the engine cylinder block and the cylinder head surface.
    2.  
    3. If the camshafts have been removed and reinstalled a waiting period dependent on the ambient temperature is necessary before mounting the cylinder head on the engine to allow the lifters to compress fully as follows:

      At room temperature: Wait 4 minutes
       
      Temperatures down to 50° F (10° C): Wait 11 minutes
       
      Temperatures lower than 50° F (10° C): Wait 30 minutes
       

    4.  


    NOTE
    This is to prevent contact between the valves and the piston tops.

    1. The engine may not be cranked under the same condition for a period of:

      Room temperature: 10 minutes
       
      Temperatures down to 50° F (10° C): 30 minutes
       
      Temperatures below 50° F (10° C): 75 minutes
       

    2.  
    3. Check the cylinder head for warpage and pressure test for coolant leakage.
    4.  


    WARNING
    Use care to not drop any pieces of gasket or debris into the oil or coolant passages.

    1. Inspect the condition and location of the head locating dowel sleeves.
    2.  
    3. Apply a bead of an elastic non-drying gasket sealant such as Drei Bond® 1209 to the seam at the top of the area where the front timing cover and the engine block meet.
    4.  
    5. Place a new head gasket on the engine block over the locating dowels.
    6.  
    7. Carefully place the cylinder head onto the engine block making sure the dowel sleeves are properly aligned and be sure that the head sits flat on the engine block.
    8.  


    WARNING
    The cylinder head bolts may not be reused.


    NOTE
    The bolts are a different length and have a different torque specification for aluminum engine blocks than those for the cast iron engine blocks.

    1. Install and torque the new cylinder head bolts in three steps, following the illustrated tightening sequence.
    2.  
    3. On cast iron engine blocks:
      1. Wash the bolts in a cleaning solvent.
      2.  
      3. Apply a light coating of oil to the head and threads of the bolts.
      4.  
      5. Torque the M10 x 95mm bolts for cast iron engine blocks using the tightening sequence as follows:

        Step 1: 22.l ft. lbs. (30 Nm)
         
        Step 2: 90°
         
        Step 3: 90°
         

      6.  

    4.  
    5. On cast aluminum engine blocks:
      1. DO NOT remove the coating on the head bolts or wash them.
      2.  
      3. Apply a light coating of oil to the head and threads of the bolts.
      4.  
      5. Torque the M10 x 110mm bolts for cast aluminum engine blocks using the tightening sequence as follows:

        Step 1: 29.5 ft. lbs. (40 Nm).
         
        Step 2: 90°.
         
        Step 3: 90°.
         

      6.  

    6.  
    7. Install the fasteners located in the recessed area near the front of the camshafts securing the front of the cylinder head to the engine block and torque to 96 inch lbs. (10 Nm).
    8.  
    9. With the attached wire secured to the crankshaft cam chain, carefully raise the chain upward and apply a light tension to the chain, then while holding the chain, carefully rotate the engine clockwise to TDC on cylinder number one.
    10.  
    11. Lock the engine in the TDC position by placing the crankshaft positioning tool No. 11 2 300 through the machined hole in the engine block, just below the starter motor located on the left lower portion of the engine block. Slide the locating dowel through the machined hole in the block and into the machined hole in the flywheel to prevent movement of the crankshaft.
    12.  
    13. Hold the camshafts TDC position by placing tool No. 11 3 240 or equivalent on the valve cover mating surface at the back of the cylinder head and onto the squared ends of the camshafts, securing the camshafts such that two sides of the squared ends are parallel with the cam cover gasket mating surface. With the camshafts in this position, the arrows on the sprockets will be facing up.
    14.  
    15. Position the crankshaft cam chain over the exhaust cam chain sprocket and install the sprocket on the exhaust cam such that the slotted holes are centered with the fastener bores in the camshaft.
    16.  
    17. Install the hydraulic cam chain tensioner, and the cam chain guide, then the intake and exhaust camshaft sprockets along with the cam chain and remove the tool used to hold the hydraulic cam chain tensioner collapsed.
    18.  
    19. Install the crankshaft cam chain tensioner assembly, spring and cap nut.
    20.  
    21. Apply gasket sealant to the upper corners of the cylinder head where the cover plate or the VANOS housing mounts and install a new gasket.
    22.  
    23. On models equipped with VANOS ;
      1. Press the helical gear of the VANOS assembly toward the housing and install the VANOS assembly. On engines with a spring plate installed on the intake camshaft, place tool No. 11-5-490 or equivalent onto the exhaust camshaft sprocket and carefully rotate the sprocket counterclockwise to allow the helical gear of the VANOS unit to thread into the intake camshaft and to allow the VANOS unit to be pulled into the front of the cylinder head.
      2.  
      3. If tool No. 11-5-490 or equivalent is not available, move the camshaft sprockets to install the VANOS by using a suitable drift and soft faced mallet and lightly tapping on a sprocket tooth of the exhaust cam sprocket to rotate both cam sprockets counterclockwise, while alternately pressing on the VANOS unit to install it. This procedure may need to be repeated several times to fully install the VANOS unit, and must be performed very carefully, in such a manner to not distort or damage the teeth of the cam sprocket.
      4.  

    24.  


    NOTE
    Make sure when assembling the VANOS unit is able to rest on the front of the cylinder head without being forced or without binding. If the VANOS unit does not fully seat it may be necessary to reposition the camshaft sprockets such that the slots in the camshaft sprockets allow enough movement of the sprockets for the helical gear of the VANOS assembly to be fully seated during assembly.

    1. Tighten the VANOS unit fastener and then torque the camshaft sprocket bolts of both the intake and exhaust cams to 16 ft. lbs. (22 Nm).
    2.  

    1. Remove the crankshaft TDC alignment tool No. 113240 or equivalent from the engine, and remove the camshaft TDC positioning tool No. 11 3 240 or equivalent from the valve cover mating surface at the back of the cylinder head.
    2.  


    WARNING
    If the camshafts have been removed and reinstalled, a waiting period dependent on the ambient temperature is necessary before rotating the crankshaft to allow the lifters to fully compress.

    1. The engine may not be cranked under these conditions for a period of:

      Room temperature: 10 minutes
       
      Temperatures down to 50° F (10° C): 30 minutes
       
      Temperatures below 50° F (10° C): 75 minutes
       

    2.  


    NOTE
    This is to prevent contact between the valves and the piston tops.

    1. Once the waiting period has expired, slowly and carefully rotate the engine clockwise four complete revolutions bringing cylinder number one to TDC. If the engine binds for any reason stop immediately to evaluate and rectify the cause of the binding.
    2.  
    3. With cylinder number one at TDC slide the camshaft TDC positioning tool No. 11-3-240 or equivalent over the ends of the cams and onto the valve cover mating surface. If the tool slides over the cams and is flush with the mating surface, the camshafts are properly timed. If the tool does not slide easily over the ends of the cams, or if the tool is not flush with the valve cover mating surface, the camshaft timing must be repeated until the tool fits squarely.
    4.  
    5. The balance of installation is the reverse of the removal procedure.
    6.  
    7. Top off the engine cooling system and bleed as necessary.
    8.  


    NOTE
    It may be necessary to bleed the cooling system a second time after the engine has been started.

    1. Change the engine oil and filter.
    2.  
    3. Check and top off all fluid levels as necessary.
    4.  
    5. Connect the negative battery cable, start the engine and check for any leaks.
    6.  

    M20 Engine
    1. Disconnect the negative battery cable. Make sure the engine is cool. Disconnect the exhaust pipes at the manifold and at the transmission clamp. Remove the drain plug at the bottom of the radiator and drain the coolant. Drain the engine oil.
    2.  
    3. Disconnect the accelerator and cruise control cables. If the vehicle has automatic transmission, disconnect the throttle cable that goes to the transmission.
    4.  
    5. Working at the front of the block, disconnect the upper radiator hose, the bypass water hose, and several smaller water hoses. Remove the diagnosis plug located at the front corner of the manifold. Remove the bracket located just underneath. Disconnect the fuel line and drain the contents into a metal container for safe disposal.
    6.  
    7. Working on the air cleaner/airflow sensor, disconnect the vacuum hoses, labeling them if necessary. Disconnect all electrical connectors and unclip and remove the wiring harness. There is a relay located in an L-shaped box near the strut tower. Disconnect and remove it. Unclamp and remove the air hose. Remove the mounting nuts and remove the assembly.
    8.  
    9. Disconnect the hose at the coolant overflow tank. Disconnect the idle speed positioner vacuum hose and then remove the positioner from the manifold.
    10.  
    11. If equipped with 4-wheel drive, disconnect the vacuum hose from the servo mounted on the manifold.
    12.  
    13. Place a drain pan underneath and then disconnect the water connections at the front of the intake manifold. Detach the electrical connector.
    14.  
    15. Disconnect the heater water hoses. Press down on the vent tube collar and install the special tool or a similar device to retain the collar in the unlocked position. Disconnect the vent tube and inspect its O-ring seal, replacing it, if necessary.
    16.  
    17. Unbolt the dipstick tube at the manifold. Remove the fuel hose bracket at the cylinder head. Make sure the engine is cold. Then, place a metal container under the connection and disconnect the fuel hose at the connection.
    18.  
    19. Disconnect the high tension lead from the coil. Disconnect and remove the coolant expansion tank.
    20.  
    21. If equipped with 4-wheel drive, disconnect the intake manifold vacuum hose leading the servo that engages 4-wheel drive.
    22.  
    23. Detach the fuel injector connectors from all 6 injectors, as well as the 2 additional electrical connectors to sensors on the head. Disconnect the oil pressure sending unit connector. Then, unfasten the carriers and remove this wiring harness toward the left side of the vehicle.
    24.  
    25. Disconnect the coil high tension wire and disconnect the high tension wires at the plugs. Then, disconnect the tube in which the wires run at the camshaft cover. Disconnect the PCV hose. Then, remove the retaining nuts and remove the camshaft cover.
    26.  
    27. Turn the crankshaft so the TDC line is aligned on the indicator and the valves of No. 6 cylinder are in overlapping, slightly open position.
    28.  
    29. Remove the distributor cap. Then, unscrew and remove the rotor. Unscrew and remove the adapter just underneath the rotor. Remove the cover underneath the adapter. Check its O-ring and replace it, if necessary.
    30.  
    31. Remove the distributor mounting bolts and the protective cover.
    32.  
    33. These engines are equipped on a rubber drive and timing belt. Remove the belt covers. To loosen belt tension, loosen the tension roller bracket pivot bolt and adjusting slot bolt. Push the roller and bracket away from the belt to release the tension, hold the bracket in this position, and tighten the adjusting slot bolt to retain the bracket it this position.
    34.  
    35. Remove the timing belt.
    36.  


    NOTE
    Make sure to avoid rotating both the engine and camshaft from this point onward

    1. Remove the cylinder head mounting bolts in three steps using the exact reverse order of the tightening sequence. Then, remove the cylinder head.
    2.  



    Click image to see an enlarged view

    Fig. To release the vent tube on the M20 engine, the collar must be held down with Tool No. 11 1 290 or equivalent



    Click image to see an enlarged view

    Fig. Cylinder head bolt torque sequencer-M20 engine

    To install:

    1. Clean both cylinder head and block sealing surfaces thoroughly with a hardwood scraper. Inspect the surfaces for flatness.
    2.  
    3. Install the cylinder head using a new gasket. Check that all passages line up with the gasket holes. Make sure all the bolt cavities are thoroughly cleaned and free of debris. Make sure to keep oil out of all the bolt cavities otherwise cracking may occur and/or the cylinder head torque will be inaccurate.
    4.  
    5. The cylinder head must be installed using new Torx® head fasteners. Before installing the cylinder head bolts, carefully wash and oil them.
    6.  


    NOTE
    New Torx® head fasteners are required for cylinder head installation. Neither the Torx® head or the hex head fasteners can be reused.

    1. Tighten the Torx® head cylinder head-to-engine block bolts as follows:
      1. Step 1: 22 ft. lbs. (30 Nm) following the cylinder head tightening sequence
      2.  
      3. Step 2: Tighten 90° following the tightening sequence
      4.  
      5. Step 3: Tighten and additional 90° following the tightening sequence
      6.  

    2.  


    NOTE
    With the No. 1 piston at Top Dead Center (TDC) of the compression stroke, make sure to align the timing marks when installing the timing belt. The crankshaft sprocket mark must point at the notch in the flange of the front engine cover. The camshaft sprocket arrow must point at the alignment mark on the cylinder head. BMW recommends that the timing belt be replaced every time the cylinder head is removed and/or the belt is disturbed. Make sure the belt is properly tensioned.

    1. Check and adjust the valves as necessary.
    2.  
    3. Complete the installation by reversing all removal procedures making sure of the following.
    4.  
    5. Change the engine oil and filter.
    6.  
    7. Top off the cooling system with the proper mixture of coolant and bleed as necessary.
    8.  
    9. Use new gaskets for the exhaust system connections, and coat the studs with an anti-seizing compound.
    10.  
    11. Install the connectors for the DME reference mark and speed signals such that the gray plug goes to the socket with a ring underneath.
    12.  
    13. Check and top off all fluid levels.
    14.  
    15. Connect the negative battery cable and check for normal operation.
    16.  

    M42 Engine
    1. Disconnect the negative battery cable.
    2.  
    3. Remove the intake manifold and the exhaust manifold as outlined in this section.
    4.  
    5. Remove the ignition coil cover and pull off the spark plug connectors.
    6.  
    7. Remove the complete ignition leads. Remove the cylinder head cover.
    8.  
    9. Disconnect the coolant hoses and remove the position sensor.
    10.  
    11. Remove the thermostat housing and thermostat. Unscrew the upper timing case cover.
    12.  
    13. Rotate the engine clockwise until the camshaft peaks of the intake and exhaust camshafts for cylinder No. 1 face each other. The arrows on the camshaft sprockets should be facing up.
    14.  
    15. Remove the chain tensioner. Remove the upper chain guide, chain guide bolt on the right side and the sprockets.
    16.  
    17. Remove the cylinder head bolts in three steps in the opposite order of the tightening sequence.
    18.  
    19. Remove the cylinder head. Clean the sealing surfaces on the cylinder head and the crankcase.
    20.  



    Click image to see an enlarged view

    Fig. Cylinder head bolt tightening sequence-M42 engine

    To install:

    1. Clean the new head bolts and the bores of the cylinder block. Do not allow oil or contaminants to fill the bores. Use a 0.012 inch (0.3mm) thicker head gasket if the head was machined.
    2.  
    3. Before installing the cylinder head;
      1. Make sure the camshafts are positioned in the cylinder head such that the camshaft is in the Top Dead Center (TDC) position for the compression stroke for cylinder number 1. In this position, the tips of the camshaft lobes for cylinder number 1 are pointing toward one another and the alignment tool No. 11 3 240 or its equivalent can be placed into position.
      2.  
      3. Install a new head gasket in the proper orientation as marked on the gasket. Check the condition of the guide dowels in the cylinder deck.
      4.  
      5. Install new seals into the top of the front timing case.
      6.  
      7. On M42 engines produced since 9.92, make sure the check valve with the rubber lined spacing sleeve for the oil supply to the cylinder head is properly installed into the engine block.
      8.  

    4.  


    WARNING
    An improperly installed check valve will cause mechanical damage to the cylinder head.


    NOTE
    New cylinder head bolts must be installed, they cannot be reused.

    1. Thoroughly wash the new cylinder head bolts and lubricate them with fresh engine oil.
    2.  
    3. Place the cylinder head onto the engine block and torque the cylinder head bolts in three steps following the illustrated tightening sequence as follows:
      1. Step 1: 22 ft. lbs. (30 Nm)
      2.  
      3. Step 2: 90°
      4.  
      5. Step 3: 90°
      6.  

    4.  


    NOTE
    During cylinder head or camshaft installation a waiting period is necessary before the camshaft timing chain can be installed to allow the hydraulic lash adjusters to bleed down and prevent the valves from contacting the pistons.

    1. If the camshafts were removed and installed while the cylinder head was removed, or if the camshafts are to be installed after the cylinder head is installed, a waiting period is necessary before the camshaft timing can be performed to allow the hydraulic lash adjusters to bleed down and prevent the valves from contacting the pistons.
    2.  

    The waiting period varies depending on the work environment's ambient air temperature. The waiting period is as follows:



    Above 68°F (20°C): 4 minutes
     
    50-67°F (10-19.4°C): 11 minutes
     
    32-49°F (0-9.4°C): 30 minutes
     

    1. Once the proper waiting period has been observed, install the camshaft alignment Tool No. 11 3 240 or its equivalent. This positions the camshafts at Top Dead Center (TDC) on the firing stroke for cylinder number 1, and the arrows on the camshaft sprockets should be facing up. If the camshaft sprockets were removed, install the sprockets with the arrows pointing up and torque to 10-12 ft. lbs. (13-17 Nm).
    2.  
    3. Pull upward and support the timing chain by hand and slowly rotate the crankshaft clockwise until cylinder number 1 is at (TDC).
    4.  
    5. Secure the engine at TDC by installing Tool No. 11 2 300 or its equivalent through the machined hole in the engine block, and into the flywheel. The machined hole in the engine block is located just below the starter motor, and is sealed with a removable plug.
    6.  
    7. Install the timing chain, timing guide bolt on the right side and the upper chain guide.
    8.  
    9. If not installing a new tensioner piston, knock the outer sleeve of the tensioner piston so the piston is released from the sleeve. Assemble the tensioner with the spring, the piston and the snaprings in position. Place in a vice and press together until both snaprings engage. If the piston starts to extend, the procedure must be done again. The compressed tensioner length should be 2.697 inches (68.5mm).
    10.  
    11. Install the tensioner into its bore and tighten the plug to 17-19 ft. lbs. (23-27 Nm). Push the tensioner rail against the tensioner to release the tensioner piston.
    12.  
    13. Remove the camshaft and crankshaft alignment tools. Install the front timing upper cover using new gaskets filling the seam gaps with a suitable non hardening sealer. Press down on the cover to align it with a the cylinder head. Install the bolts and torque to 53-62 inch lbs. (8-10 Nm) for M6 bolts and 15-17 ft. lbs. (20-22 Nm) for M8 bolts.
    14.  
    15. Install the thermostat housing using a new gasket and torque to 53-62 inch lbs. (8-10 Nm).
    16.  


    NOTE
    Make sure the vent hole on the thermostat faces up.

    1. Install the camshaft position sensor.
    2.  
    3. The balance of installation is in reverse order of removal noting the following.
    4.  
    5. Fill and bleed the cooling system with the proper mixture of coolant.
    6.  
    7. Change the engine oil and filter.
    8.  
    9. Check and top off all fluid levels.
    10.  
    11. Connect the negative battery cable and check for normal operation.
    12.  

    M44 1.9L Engines
    1. Before servicing the vehicle, refer to the precautions in the beginning of this section.
    2.  
    3. Drain the cooling system.
    4.  
    5. Relieve the fuel system pressure.
    6.  
    7. Remove or disconnect the following:

      Negative battery cable
       
      Fuel feed and return lines
       
      Intake manifold
       
      Ignition coil cover and remove the spark plug connectors
       
      All the fasteners securing the brackets for the ignition coil wire harness, then move the harness aside to access the cylinder head cover
       
      Cylinder head cover
       
      Coolant hoses and temperature sensor
       
      Thermostat housing and thermostat
       
      Upper timing case cover
       

    8.  
    9. Rotate the engine in the direction of the rotation until the camshaft peaks of the intake and exhaust camshafts for cylinder No. 1 face each other. The arrows on the cam sprocket should face up.
    10.  
    11. Remove or disconnect the following:

      Chain tensioner, the upper chain guide, the chain guide bolt on the right side and the camshaft sprockets
       
      Cylinder head bolts in the reverse order of the tightening sequence (from the outside to the inside) in at least 3 steps
       
      Cylinder head
       

    12.  

    To install:

    Click image to see an enlarged view

    Fig. Cylinder head torque sequence-M44B19 1.9L engine

    1. Install the cylinder head with a new gasket and bolts. Tighten the bolts in sequence as follows:

      Step 1: 22 ft. lbs. (30 Nm)
       
      Step 2: +90 degrees
       
      Step 3: +90 degrees
       

    2.  
    3. The balance of installation is the reverse of the removal procedure.
    4.  
    5. Fill the cooling system.
    6.  
    7. Start the engine and check for leaks.
      NOTE
      It may be necessary to bleed the cooling system a second time after the engine has been started.

    8.  

     
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