Most engine overhaul procedures are fairly standard. In addition to specific parts replacement procedures and specifications for your individual engine, this section is also a guide to acceptable rebuilding procedures. Examples of standard rebuilding practice are given and should be used along with specific details concerning your particular engine.
Competent and accurate machine shop services will ensure maximum performance, reliability and engine life. In most instances it is more profitable for the do-it-yourself mechanic to remove, clean and inspect the component, buy the necessary parts and deliver these to a shop for actual machine work.
Much of the assembly work (crankshaft, bearings, piston rods, and other components) is well within the scope of the do-it-yourself mechanic's tools and abilities. You will have to decide for yourself the depth of involvement you desire in an engine repair or rebuild.
Aluminum has become extremely popular for use in engines, due to its low weight. Observe the following precautions when handling aluminum parts:
When assembling the engine, any parts that will be exposed to frictional contact must be prelubed to provide lubrication at initial start-up. Any product specifically formulated for this purpose can be used, but engine oil is not recommended as a prelube in most cases.
When semi-permanent (locked, but removable) installation of bolts or nuts is desired, threads should be cleaned and coated with Loctite®or another similar, commercial non-hardening sealant.Buy or Rebuild-
Now that you have determined that your engine is worn out, you must make some decisions. The question of whether or not an engine is worth rebuilding is largely a subjective matter and one of personal worth. Is the engine a popular one, or is it an obsolete model- Are parts available- Are special tools available. The Dual Over Head Camshaft engines (3.4L VIN X and 3.5L VIN H) require special camshaft holding fixtures for most procedures. If they are not available, you will have great difficulty servicing these engines. Will it get acceptable gas mileage once it is rebuilt- Is the car it's being put into worth keeping- Would it be less expensive to buy a new engine, have your engine rebuilt by a pro, rebuild it yourself or buy a used engine from a salvage yard- Or would it be simpler and less expensive to buy another car- If you have considered all these matters and more, and have still decided to rebuild the engine, then it is time to decide how you will rebuild it.
A complete rebuild or overhaul of an engine involves replacing all of the moving parts (pistons, rods, crankshaft, camshaft, etc.) with new ones and machining the non-moving wearing surfaces of the block and heads. Unfortunately, this may not be cost effective. For instance, your crankshaft may have been damaged or worn, but it can be machined undersize for a minimal fee.
So, as you can see, you can replace everything inside the engine, but, it is wiser to replace only those parts which are really needed, and, if possible, repair the more expensive ones.
In the real world, where time and convenience often count more than money, a worn out engine can be simply replaced with one of the following choices:
Swapping in a rebuilt long block or good used engine is the solution most individuals and even professional shops will use. It is the quickest, and often the least expensive way to return the vehicle to service. On today's front-wheel drive cars, removing and installing an engine can be long, arduous task. Most individuals and certainly all professional shops will only want to do the job once. Installing an engine rebuilt at home, then having to remove it again (perhaps several times) because some component failed, was incorrectly installed, is out of specification or some leak needs to be corrected, can be most discouraging. Professional engine builders deal in such volume that their prices for an assembled, reconditioned engine may be less than the cost of buying parts, having other components reconditioned and then assembling the engine yourself. Dealership parts departments can often order a so-called "crate motor" which is a factory reconditioned or even brand new engine, at surprisingly reasonable prices. You simply open the "crate", transfer a few components from your engine, and you're ready for installation. A new engine (keep the receipt) should have a warranty and may even enhance the resale value of your vehicle.
If you choose to recondition the engine yourself, look into engine rebuild kits. Most popular engines have kits available containing the major components. The crankshaft is generally reconditioned to a standard undersize and matching oversize bearings are included. Pistons and rings, oil pumps, timing chain sets and gasket sets are available. Since the major components in a rebuild kit are reconditioned, or even new, it takes the guesswork out of precision measuring (if you have the proper tools) and evaluating used parts. These kits, purchased from a reliable supplier and carefully installed in your clean and prepared engine block, can produce a successful overhaul.
Later in this section, we will break the engine down into its two main components: the cylinder head and the engine block. We will discuss each component, and the recommended parts to replace during a rebuild on each.Cylinder Block Reconditioning
A thorough overhaul or rebuild of an engine block would include replacing the pistons, rings, bearings, timing belt/chain assembly and oil pump. For OHV engines also include a new camshaft and lifters. The block would then have the cylinders bored and honed and the crankshaft would be reground to a standard undersize to provide new wearing surfaces and acceptable clearances. However, your particular engine may not have everything worn out. What if only the piston rings have worn out and the clearances on everything else are still within factory specifications- You could just replace the rings and put it back together, but this would be a very rare example. Chances are, if one component in your engine is worn, other components are sure to follow, and soon. At the very least, you should always replace the rings, bearings and oil pump.Assembly
Before you begin assembling the engine, first give yourself a clean, dirt free work area. Next, clean every engine component again. The key to a good assembly is cleanliness.
Mount the engine block into the engine stand and wash it one last time using water and detergent (dishwashing detergent works well). While washing it, scrub the cylinder bores with a soft bristle brush and thoroughly clean all of the oil passages. Completely dry the engine and spray the entire assembly down with an anti-rust solution such as WD-40® or similar product. Take a clean lint-free rag and wipe up any excess anti-rust solution from the bores, bearing saddles, etc. Repeat the final cleaning process on the crankshaft. Replace any freeze or oil galley plugs which were removed during disassembly.Crankshaft
- Remove the main bearing inserts from the block and bearing caps.
- If the crankshaft main bearing journals have been refinished to a definite undersize, install the correct undersize bearing. Be sure that the bearing inserts and bearing bores are clean. Foreign material under inserts will distort bearing and cause failure.
- Place the upper main bearing inserts in bores with tang in slot.
- Install the lower main bearing inserts in bearing caps.
- Clean the mating surfaces of block and rear main bearing cap.
- Carefully lower the crankshaft into place. Be careful not to damage bearing surfaces.
Check the clearance of each main bearing by using the following procedure:
- Place a piece of Plastigage®or its equivalent, on bearing surface across full width of bearing cap and about 1 / 4 in. off center.
- Install cap and tighten bolts to specification. Do not turn crankshaft while Plastigage® is in place.
- Remove the cap. Using the supplied Plastigage® scale, check width of Plastigage® at widest point to get maximum clearance. Difference between readings is taper of journal.
- If clearance exceeds specified limits, it may be possible to special-order a 0.001 in. or 0.002 in. undersize bearing. Bearing clearance must be within specified limits. If standard and 0.002 in. undersize bearing does not bring clearance within desired limits, the crankshaft will have to be sent to an automotive machine shop to refinish the crankshaft journal, then install undersize bearings. A more likely solution is to exchange to damaged crankshaft for a reconditioned crankshaft kit that should come with matching bearings, and usually, reconditioned connecting rods, too.
- After the bearings have been fitted, apply a light coat of engine oil to the journals and bearings. Install the rear main bearing cap. Install all bearing caps except the thrust bearing cap. The thrust bearing has side flanges on it an it absorbs the wear of the crankshaft moving slightly forward and backward in the engine block during operation. Be sure that main bearing caps are installed in original locations. This is very important. If the bearing caps are install out-of-position or backwards, you will quickly fail the engine, if it turns over at all. Tighten the bearing cap bolts to specifications.
- Install the thrust bearing cap with bolts finger-tight.
- Pry the crankshaft forward against the thrust surface of upper half of bearing.
- Hold the crankshaft forward and pry the thrust bearing cap to the rear. This aligns the thrust surfaces of both halves of the bearing.
- Retain the forward pressure on the crankshaft. Tighten the cap bolts to specifications.
- Measure the crankshaft end-play as follows:
- Mount a dial gauge to the engine block and position the tip of the gauge to read from the crankshaft end.
- Carefully pry the crankshaft toward the rear of the engine and hold it there while you zero the gauge.
- Carefully pry the crankshaft toward the front of the engine and read the gauge.
- Confirm that the reading is within specifications. If not, install a new thrust bearing and repeat the procedure. If the reading is still out of specifications with a new bearing, have a machine shop inspect the thrust surfaces of the crankshaft, and if possible, repair it.
- Rotate the crankshaft so as to position the first rod journal to the bottom of its stroke.
The installation procedures for the following components may be found earlier in this section.
Install the timing cover(s) and oil pan. Refer to your notes and drawings made prior to disassembly and install all of the components that were removed. Install the engine into the vehicle.OHC Engines
The installation procedures for the following components may be found earlier in this section.
- Install the cylinder head(s) using new gaskets.
- Install the timing sprockets/gears and the belt/chain assemblies.
Camshaft, Lifters And Timing Assembly
The installation procedures for the following components may be found earlier in this section.
- Install the camshaft.
- Install the lifters/followers into their bores.
- Install the timing gears/chain assembly.
The installation procedures for the following components may be found earlier in this section.
- Install the cylinder head(s) using new gaskets.
- Assemble the rest of the valve train (pushrods and rocker arms and/or shafts).
Before installing the piston/connecting rod assembly, oil the pistons, piston rings and the cylinder walls with light engine oil. Install connecting rod bolt protectors or rubber hose onto the connecting rod bolts/studs. Also perform the following:
- Select the proper ring set for the size cylinder bore.
- Position the ring in the bore in which it is going to be used.
- Push the ring down into the bore area where normal ring wear is not encountered.
- Use the head of the piston to position the ring in the bore so that the ring is square with the cylinder wall. Use caution to avoid damage to the ring or cylinder bore.
- Measure the gap between the ends of the ring with a feeler gauge. Ring gap in a worn cylinder is normally greater than specification. If the ring gap is greater than the specified limits, try an oversize ring set.
- Check the ring side clearance of the compression rings with a feeler gauge inserted between the ring and its lower land according to specification. The gauge should slide freely around the entire ring circumference without binding. Any wear that occurs will form a step at the inner portion of the lower land. If the lower lands have high steps, the piston should be replaced.
- Unless new pistons are installed, be sure to install the pistons in the cylinders from which they were removed. The numbers on the connecting rod and bearing cap must be on the same side when installed in the cylinder bore. If a connecting rod is ever transposed from one engine or cylinder to another, new bearings should be fitted and the connecting rod should be numbered to correspond with the new cylinder number. The notch on the piston head goes toward the front of the engine.
- Install all of the rod bearing inserts into the rods and caps.
- Install the rings to the pistons. Install the oil control ring first, then the second compression ring and finally the top compression ring. Use a piston ring expander tool to aid in installation and to help reduce the chance of breakage.
- Make sure the ring gaps are properly spaced around the circumference of the piston. Fit a piston ring compressor around the piston and slide the piston and connecting rod assembly down into the cylinder bore, pushing it in with the wooden hammer handle. Push the piston down until it is only slightly below the top of the cylinder bore. Don't forget to install some short lengths of rubber hose on the connecting rod bolts to protect the crankshaft. The connecting rod bolts are hardened and the threads are sharp enough to nick the crankshaft journal. That will ruin the bearing and fail the engine shortly after start-up. Guide the connecting rod onto the crankshaft bearing journal carefully, to avoid damaging the crankshaft.
- Check the bearing clearance of all the rod bearings, fitting them to the crankshaft bearing journals. Follow the procedure in the crankshaft installation above.
- After the bearings have been fitted, apply a light coating of assembly oil to the journals and bearings.
- Turn the crankshaft until the appropriate bearing journal is at the bottom of its stroke, then push the piston assembly all the way down until the connecting rod bearing seats on the crankshaft journal. Be careful not to allow the bearing cap screws to strike the crankshaft bearing journals and damage them.
- After the piston and connecting rod assemblies have been installed, check the connecting rod side clearance on each crankshaft journal.
- If required, install the balance shaft following the procedures found earlier in this section.
- Install the rear crankshaft oil seal.
Before the engine and its components are inspected, they must be thoroughly cleaned. You will need to remove any engine varnish, oil sludge and/or carbon deposits from all of the components to insure an accurate inspection. A crack in the engine block or cylinder head can easily become overlooked if hidden by a layer of sludge or carbon.
Most of the cleaning process can be carried out with common hand tools and readily available solvents or solutions. Carbon deposits can be chipped away using a hammer and a hard wooden chisel. Old gasket material and varnish or sludge can usually be removed using a scraper and/or cleaning solvent. Extremely stubborn deposits may require the use of a power drill with a wire brush. If using a wire brush, use extreme care around any critical machined surfaces (such as the gasket surfaces, bearing saddles, cylinder bores, etc.). Use of a wire brush is NOT RECOMMENDED on any aluminum components. Always follow any safety recommendations given by the manufacturer of the tool and/or solvent. You should always wear eye protection during any cleaning process involving scraping, chipping or spraying of solvents.
An alternative to the mess and hassle of cleaning the parts yourself is to drop them off at a local garage or machine shop. They will, more than likely, have the necessary equipment to properly clean all of the parts for a nominal fee.
Remove any oil galley plugs, freeze plugs and/or pressed-in bearings and carefully wash and degrease all of the engine components including the fasteners and bolts. Small parts such as the valves, springs, etc., should be placed in a metal basket and allowed to soak. Use pipe cleaner type brushes, and clean all passageways in the components. Use a ring expander and remove the rings from the pistons. Clean the piston ring grooves with a special tool or a piece of broken ring. Scrape the carbon off of the top of the piston. You should never use a wire brush on the pistons. After preparing all of the piston assemblies in this manner, wash and degrease them again.
When cleaning the cylinder head, remove carbon from the combustion chamber with the valves installed. This will avoid damaging the valve seats.
An automobile engine is a combination of many machined, honed, polished and lapped surfaces with tolerances that are measured in the ten-thousandths of an inch. When any internal engine parts are serviced, care and cleanliness are important. A liberal coating of engine oil should be applied to friction areas during assembly in order to protect and lubricate the surfaces on initial operation. Throughout this section, it should be understood that proper cleaning and protection of machined surfaces and friction areas is part of the repair procedure. This is considered standard shop practice even if not specifically stated.
Whenever the valve train components are removed for service, they should be kept in order. This should be done in order to install the parts in the same locations and with the same mating surfaces as when removed.
The battery cables should be disconnected before any major work is performed on the engine. Failure to disconnect the cables may result in damage to the wire harness or other electrical parts.Disassembly
The engine disassembly instructions following assume that you have the engine mounted on an engine stand. If not, it is easiest to disassemble the engine on a bench or the floor with it resting on the bell housing or transmission mounting surface. You must be able to access the connecting rod fasteners and turn the crankshaft during disassembly. Also, all engine covers (timing, front, side, oil pan, whatever) should have already been removed. Engines which are seized or locked up may not be able to be completely disassembled, and a core (salvage yard) engine should be purchased.
Rotate the engine over so that the crankshaft is exposed. Use a number punch or scribe and mark each connecting rod with its respective cylinder number. The cylinder closest to the front of the engine is always number 1. However, depending on the engine placement, the front of the engine could either be the flywheel or damper/pulley end. Generally the front of the engine faces the front of the vehicle. Use a number punch or scribe and also mark the main bearing caps from front to rear with the front most cap being number 1 (if there are five caps, mark them 1 through 5, front to rear).
With the engine still on a rotating engine stand, turn the engine to position the #1 cylinder bore (head surface) up. Turn the crankshaft until the #1 piston is at the bottom of its travel. This should allow the maximum access to its connecting rod. Remove the #1 connecting rod's fasteners and cap and place two lengths of rubber hose over the rod bolts/studs to protect the crankshaft from damage. Using a sturdy wooden dowel and a hammer, push the connecting rod up about 1 in. (25mm) from the crankshaft and remove the upper bearing insert. Continue pushing or tapping the connecting rod up until the piston rings are out of the cylinder bore. Remove the piston and rod by hand, put the upper half of the bearing insert back into the rod, install the cap with its bearing insert installed, and hand-tighten the cap fasteners. If the parts are kept in order in this manner, they will not get lost and you will be able to tell which bearings came from what cylinder if any problems are discovered and diagnosis is necessary. Remove all the other piston assemblies in the same manner. On the V6 engines covered by this product, remove all of the pistons from one bank, then reposition the engine with the other cylinder bank head surface up, and remove that banks piston assemblies.
The only remaining component in the engine block should now be the crankshaft. Loosen the main bearing caps evenly until the fasteners can be turned by hand, then remove them and the caps. Remove the crankshaft from the engine block. Thoroughly clean all of the components.OHC Engines
If not done during the cylinder head removal, remove the timing chain/belt and/or gear/sprocket assembly. Remove the oil pick-up and pump assembly and, if necessary, the pump drive. If equipped, remove any balance or auxiliary shafts. If necessary, remove the cylinder ridge from the top of the bore. See the cylinder ridge removal procedure earlier in this section.Ohv Engines
If not done during the cylinder head removal, remove the pushrods and lifters, keeping them in order for assembly. Remove the timing gears and/or timing chain assembly, then remove the oil pump drive assembly and withdraw the camshaft from the engine block. Remove the oil pick-up and pump assembly. If equipped, remove any balance or auxiliary shafts. If necessary, remove the cylinder ridge from the top of the bore. See the cylinder ridge removal procedure earlier in this section.Inspection
With the engine block and all of its components clean, inspect for wear and/or damage. To accurately inspect them, you will need some specialized tools:
If you do not have access to the proper tools, you may want to bring the components to a shop that does.
Generally, you shouldn't expect cracks in the engine block or its components unless it was known to leak, consume or mix engine fluids, it was severely overheated, or there was evidence of bad bearings and/or crankshaft damage. A visual inspection should be performed on all of the components, 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). Zyglo®uses a spray on fluorescent mixture along with a black light to reveal the cracks. It is strongly recommended to have your engine block 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.Bearings
All of the engine bearings should be visually inspected for wear and/or damage. The bearing should look evenly worn all around with no deep scores or pits. If the bearing is severely worn, scored, pitted or heat blued, then the bearing, and the components that use it, should be brought to a machine shop for inspection. Full-circle bearings (used on most camshafts, auxiliary shafts, balance shafts, etc.) require specialized tools for removal and installation, and should be brought to a machine shop for service.Engine Block
Checking The Block Deck For Warpage
The top of the engine block where the cylinder head mounts is called the "deck." Insure that the deck surface is clean of dirt, carbon deposits and old gasket material. Place a straightedge across the surface of the deck along its centerline and, using feeler gauges, check the clearance along several points. Repeat the checking procedure with the straightedge placed along both diagonals of the deck surface. If the reading 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 deck, it must be machined.Cylinder Bores
The cylinder bores house the pistons and are slightly larger than the pistons themselves. A common piston-to-bore clearance is 0.0015-0.0025 in. (0.0381mm-0.0635mm). Inspect and measure the cylinder bores. The bore should be checked for out-of-roundness, taper and size. The results of this inspection will determine whether the cylinder can be used in its existing size and condition, or a rebore to the next oversize is required (or in the case of removable sleeves, have replacements installed).
The amount of cylinder wall wear is always greater at the top of the cylinder than at the bottom. This wear is known as taper. Any cylinder that has a taper of 0.0012 in. (0.305mm) or more, must be rebored. Measurements are taken at a number of positions in each cylinder: at the top, middle and bottom and at two points at each position; that is, at a point 90 degrees from the crankshaft centerline, as well as a point parallel to the crankshaft centerline. The measurements are made with either a special dial indicator or a telescopic gauge and micrometer. If the necessary precision tools to check the bore are not available, take the block to a machine shop and have them mike it. Also if you don't have the tools to check the cylinder bores, chances are you will not have the necessary devices to check the pistons, connecting rods and crankshaft. Take these components with you and save yourself an extra trip.
For our procedures, we will use a telescopic gauge and a micrometer. You will need one of each, with a measuring range which covers your cylinder bore size.
- Position the telescopic gauge in the cylinder bore, loosen the gauges lock and allow it to expand.
- Hold the gauge square in the bore, 90 degrees from the crankshaft centerline, and gently tighten the lock. Tilt the gauge back to remove it from the bore.
- Measure the gauge with the micrometer and record the reading.
- Again, hold the gauge square in the bore, this time parallel to the crankshaft centerline, and gently tighten the lock. Again, you will tilt the gauge back to remove it from the bore.
- Measure the gauge with the micrometer and record this reading. The difference between these two readings is the out-of-round measurement of the cylinder.
- Repeat steps 1 through 5, each time going to the next lower position, until you reach the bottom of the cylinder. Then go to the next cylinder, and continue until all of the cylinders have been measured.
The difference between these measurements will tell you all about the wear in your cylinders. The measurements which were taken 90 degrees from the crankshaft centerline will always reflect the most wear. That is because at this position is where the engine power presses the piston against the cylinder bore the hardest. This is known as thrust wear. Take your top, 90 degree measurement and compare it to your bottom, 90 degree measurement. The difference between them is the taper. When you measure your pistons, you will compare these readings to your piston sizes and determine piston-to-wall clearance.Engine Block Bearing Alignment
Remove the main bearing caps and, if still installed, the main bearing inserts. Inspect all of the main bearing saddles and caps for damage, burrs or high spots. If damage is found, and it is caused from a spun main bearing, the block will need to be align-bored or, if severe enough, replacement. Any burrs or high spots should be carefully removed with a metal file.
Place a straightedge on the bearing saddles, in the engine block, along the centerline of the crankshaft. If any clearance exists between the straightedge and the saddles, the block must be align-bored.
Align-boring consists of machining the main bearing saddles and caps by means of a flycutter that runs through the bearing saddles.Refinishing
Almost all engine block refinishing must be performed by a machine shop. If the cylinders are not to be bored, then the cylinder glaze should be removed with a cylinder hone. Two types are in general use. A "ball hone" uses round marble-like balls of hard abrasive on flexible wire arms. Driven by a power drill, it breaks up the glazing on the cylinder walls. The second, more expensive type of hone uses abrasive stones to perform the same job. Hones using abrasive stones, when used by a skilled automotive machine shop technician using special power hone equipment, can produce precisely reconditioned cylinder walls equal to or better than factory-original finish. Both types of hones will leave very tiny scratches in the cylinder walls which trap and hold engine oil to provide piston ring lubrication, always important, but especially during engine break-in. When removing cylinder glaze with any hone, use a light or penetrating type oil to lubricate the hone. Do not allow the hone to run dry as this may cause excessive scoring of the cylinder bores and wear on the hone. If new pistons are required, they will need to be installed to the connecting rods. This should be performed by a machine shop as the pistons must be installed in the correct relationship to the rod or engine damage can occur.
Because the top piston ring does not travel to the very top of the cylinder, a ridge of unworn cylinder wall is left between the end of the travel and the top of the cylinder bore.
Pushing the piston and connecting rod assembly past the ridge can be difficult, and damage to the piston ring lands could occur. If the ridge is not removed before installing a new piston or not removed at all, piston ring breakage and piston damage may occur.
There are several different types of ridge reamers on the market, none of which are inexpensive. Unless a great deal of engine rebuilding is anticipated, borrow or rent a cylinder ridge reamer.
- Turn the crankshaft until the piston is at the bottom of its travel.
- Cover the head of the piston with a rag.
- Follow the tool manufacturers instructions and cut away the ridge, exercising extreme care to avoid cutting too deeply.
- Remove the ridge reamer, the rag and as many of the cuttings as possible. Continue until all of the cylinder ridges have been removed.
Anything that generates heat and/or friction will eventually burn or wear out (for example, a light bulb generates heat, therefore its life span is limited). With this in mind, a running engine generates tremendous amounts of both; friction is encountered by the moving and rotating parts inside the engine and heat is created by friction and combustion of the fuel. However, the engine has systems designed to help reduce the effects of heat and friction and provide added longevity. The oiling system reduces the amount of friction encountered by the moving parts inside the engine, while the cooling system reduces heat created by friction and combustion. If either system is not maintained, a break-down will be inevitable. Therefore, you can see how regular maintenance can affect the service life of your vehicle. If you do not drain, flush and refill your cooling system at the proper intervals, deposits will begin to accumulate in the radiator, thereby reducing the amount of heat it can extract from the coolant. The same applies to your oil and filter; if it is not changed often enough it becomes laden with contaminates and is unable to properly lubricate the engine. This increases friction and wear.
There are a number of methods for evaluating the condition of your engine. A compression test can reveal the condition of your pistons, piston rings, cylinder bores, head gasket(s), valves and valve seats. An oil pressure test can warn you of possible engine bearing, or oil pump failures. Excessive oil consumption, evidence of oil in the engine air intake area and/or bluish smoke from the tailpipe may indicate worn piston rings, worn valve guides and/or valve seals. As a general rule, an engine that uses no more than one quart of oil every 1000 miles is in good condition. Engines that use one quart of oil or more in less than 1000 miles should first be checked for oil leaks. If any oil leaks are present, have them fixed before determining how much oil is consumed by the engine, especially if blue smoke is not visible at the tailpipe.Compression Test
A noticeable lack of engine power, excessive oil consumption and/or poor fuel mileage measured over an extended period are all indicators of internal engine wear. Worn piston rings, scored or worn cylinder bores, blown head gaskets, sticking or burnt valves, and worn valve seats are all possible culprits. A check of each cylinder's compression will help locate the problem.
- Make sure that the proper amount and viscosity of engine oil is in the crankcase, then ensure the battery is fully charged.
- Warm-up the engine to normal operating temperature, then shut the engine OFF .
- Disable the ignition system.
- Label and disconnect all of the spark plug wires from the plugs.
- Thoroughly clean the cylinder head area around the spark plug ports, then remove the spark plugs.
- Set the throttle plate to the fully open (wide-open throttle) position. You can block the accelerator linkage open for this, or you can have an assistant fully depress the accelerator pedal.
- Install a screw-in type compression gauge into the No. 1 spark plug hole until the fitting is snug.
- According to the tool manufacturer's instructions, connect a remote starting switch to the starting circuit.
- With the ignition switch in the OFF position, use the remote starting switch to crank the engine through at least five compression strokes (approximately 5 seconds of cranking) and record the highest reading on the gauge.
- Repeat the test on each cylinder, cranking the engine approximately the same number of compression strokes and/or time as the first.
- Compare the highest readings from each cylinder to that of the others. The indicated compression pressures are considered within specifications if the lowest reading cylinder is within 75 percent of the pressure recorded for the highest reading cylinder. For example, if your highest reading cylinder pressure was 150 psi (1034 kPa), then 75 percent of that would be 113 psi (779 kPa). So the lowest reading cylinder should be no less than 113 psi (779 kPa).
- If a cylinder exhibits an unusually low compression reading, use a squirt-type oil can and introduce about a tablespoon of clean engine oil into the cylinder through the spark plug hole and repeat the compression test. If the compression rises after adding oil, it means the oil has made a temporary seal where the rings meet the cylinder walls. It shows that the cylinder's piston rings and/or cylinder bore are damaged or worn. If, on the other hand, the pressure remains low, the valves may not be seating properly (a valve job is needed), or the head gasket may be blown near that cylinder. If compression in any two adjacent cylinders is low, and if the addition of oil doesn't help raise compression, there is leakage past the head gasket. A quick of the oil dipstick is another indicator. If the dipstick has a light-brown foamy substance looking like melted ice cream, it's a dead giveaway that there is water in the oil and the engine has major problems, such as a blown head gasket. Oil in the cooling system is another indicator of a blown head gasket. Oil and coolant in the combustion chamber, combined with blue or constant white smoke from the tailpipe, may be yet another symptom of this problem. However, don't be alarmed by the normal white smoke emitted from the tailpipe during engine warm-up or from cold weather driving.
Check for proper oil pressure at the sending unit passage with an externally mounted mechanical oil pressure gauge (as opposed to relying on a factory installed dash-mounted gauge). A tachometer may also be needed, as some specifications may require running the engine at a specific rpm.
- With the engine cold, locate and remove the oil pressure sending unit. On some engines, this may be a real challenge. In general, accessibility to the oil pressure sending unit determines whether this test can be done.
- Following the manufacturer's instructions, connect a mechanical oil pressure gauge and, if necessary, a tachometer to the engine.
- Start the engine and allow it to idle.
- Check the oil pressure reading when cold and record the number. You may need to run the engine at a specified rpm, so check the specifications.
- Run the engine until normal operating temperature is reached (upper radiator hose will feel warm).
- Check the oil pressure reading again with the engine hot and record the number. Turn the engine OFF .
- Compare your hot oil pressure reading to that given in the chart. If the reading is low, check the cold pressure reading against the chart. If the cold pressure is well above the specification, and the hot reading was lower than the specification, you may have the wrong viscosity oil in the engine. Change the oil, making sure to use the proper grade and quantity, then repeat the test.
Low oil pressure readings could be attributed to internal component wear, pump related problems, a low oil level, or oil viscosity that is too low. High oil pressure readings could be caused by an overfilled crankcase, too high of an oil viscosity or a faulty pressure relief valve.Engine Preparation
To properly rebuild an engine, you must first remove it from the vehicle, then disassemble and diagnose it. Ideally you should place your engine on an engine stand. This affords you the best access to the engine components. Follow the manufacturer's directions for using the stand with your particular engine. Remove the flywheel before installing the engine to the stand.
Now that you have the engine on a stand, and assuming that you have drained the oil and coolant from the engine, it's time to strip it of all but the necessary components. Before you start disassembling the engine, you may want to take a moment to draw some pictures, or fabricate some labels or containers to mark the locations of various components and the bolts and/or studs which fasten them. Modern day engines use a lot of little brackets and clips which hold wiring harnesses and such, and these holders are often mounted on studs and/or bolts that can be easily mixed up. The manufacturer spent a lot of time and money designing your vehicle, and they wouldn't have wasted any of it by haphazardly placing brackets, clips or fasteners on the vehicle. If it's present when you disassemble it, put it back when you assemble, you will regret not remembering that little bracket which holds a wire harness out of the path of a rotating part.
You should begin by unbolting any accessories still attached to the engine, such as the water pump, power steering pump, alternator, etc. Then, unfasten any manifolds (intake or exhaust) which were not removed during the engine removal procedure. Finally, remove any covers remaining on the engine such as the rocker arm, front or timing cover and oil pan. Some front covers may require the vibration damper and/or crank pulley to be removed beforehand. The idea is to reduce the engine to the bare necessities (cylinder head(s), valve train, engine block, crankshaft, pistons and connecting rods), plus any other 'in block' components such as oil pumps, balance shafts and auxiliary shafts.
Finally, remove the cylinder head(s) from the engine block and carefully place on a bench. Disassembly instructions for each component follow later in this section.Engine Start-Up And Break-In
Breaking It In
Make the first miles on the new engine, easy ones. Vary the speed but do not accelerate hard. Most importantly, do not lug the engine, and avoid sustained high speeds until at least 100 miles. Check the engine oil and coolant levels frequently. Expect the engine to use a little oil until the piston rings seat. Change the oil and filter at 500 miles, 1500 miles, then every 3000 miles after that.Starting The Engine
With the engine installed and every wire and hose is properly connected, take the time to go back and double check that all coolant and vacuum hoses are connected. Check that your oil drain plug is installed and properly tightened. If not already done, install a new oil filter onto the engine. Fill the crankcase with the proper amount and grade of engine oil. Fill the cooling system with a 50/50 mixture of coolant/water.
- Connect the vehicle battery.
- Start the engine. Keep your eye on your oil pressure indicator; if it does not indicate oil pressure within 10 seconds of starting, turn the vehicle off.
- Confirm that there are no fluid leaks (oil or other).
- Allow the engine to reach normal operating temperature (the upper radiator hose will be hot to the touch).
- At this point you can perform any necessary checks or adjustments, such as checking the ignition timing.
- Install any remaining components or body panels which were removed.
When raising or supporting the engine for any reason, do not use a jack under the oil pan. Due to the small clearance between the oil pan and the oil pump screen, jacking against he oil pan may cause the pan to be bent against the pump screen resulting in a damaged oil pickup unit.
Anytime the air cleaner and ducting is disconnected, the intake opening should be covered. This is to protect against accidental entrance of foreign material which should follow the intake passage into the cylinder and cause extensive damage when the engine is started.
Work in a clean and well lit area. You should have on hand: a suitable parts cleaning tank, compressed air supply, tray to keep parts and fasteners organized and an adequate set of hand tools. An approved engine repair stand will help prevent personal injury or damage to the engine components. Precision measuring tools are required for inspection of certain critical components. Torque wrenches are necessary for the correct assembly of various parts.Repairing Damaged Threads
Several methods of repairing damaged threads are available. Heli-Coil® (shown here), Keenserts® and Microdot® are among the most widely used. All involve basically the same principle-drilling out stripped threads, tapping the hole and installing a prewound insert-making welding, plugging and oversize fasteners unnecessary.
Two types of thread repair inserts are usually supplied: a standard type for most inch coarse, inch fine, metric course and metric fine thread sizes and a spark lug type to fit most spark plug port sizes. Consult the individual tool manufacturer's catalog to determine exact applications. Typical thread repair kits will contain a selection of prewound threaded inserts, a tap (corresponding to the outside diameter threads of the insert) and an installation tool. Spark plug inserts usually differ because they require a tap equipped with pilot threads and a combined reamer/tap section. Most manufacturers also supply blister-packed thread repair inserts separately in addition to a master kit containing a variety of taps and inserts plus installation tools.
Before attempting to repair a threaded hole, remove any snapped, broken or damaged bolts or studs. Penetrating oil can be used to free frozen threads. The offending item can usually be removed with locking pliers or using a screw/stud extractor. After the hole is clear, the thread can be repaired, as shown in the series of accompanying illustrations and in the kit manufacturer's instructions.Replacing Engine Gaskets
Do not reuse any gasket unless otherwise specified. Gaskets that can be reused will be identified. Do not apply sealant to any gasket or sealing surface unless directed to do so.
Use a rubber mallet to separate components. Bump the part sideways to loosen the components. Bumping should be done at bends or reinforced areas to prevent distortion of parts.
Remove all gasket and sealing material from the part using a plastic or wood scraper. Care must be used to avoid gouging or scraping sealing surfaces. Do not use any other method or technique to remove gasket material from a part. Do not use abrasive pads, sand paper or power tools to clean gasket surfaces. These methods of cleaning can damage the part. Abrasive pads also produce a fine grit that the oil filter cannot remove from the oil. The grit is abrasive and has been known to cause internal engine damage.
When assembling components, use only the sealant specified. Sealing surfaces should be clean and free of debris or oil. When applying sealant to a component, apply a bead size as specified in the service procedure. Do not allow the sealant to enter into any blind threaded holes, as it may prevent the bolt from seating properly or cause damage when the bolt is tightened.
Tighten bolts to specification. Do not overtighten.Separating Parts
In addition to its sealing capabilities, RTV sealants can form an adhesive bond between parts that can make them difficult to remove or separate. RTV is weakest in shear strength and parts should be bumped sideways if possible, rather than using prying tools to remove them. This technique should prevent part damage when the bonding strength of the RTV is stronger than the part itself. Any bumping should be done at bends or reinforced areas to prevent part distortion.Tools
The tools required for an engine overhaul or parts replacement will depend on how much work you will be doing yourself. With a few exceptions, they will be the tools found in a mechanic's tool kit (see Section 1 of this manual). More in-depth work will require some or all of the following:
The use of most of these tools is illustrated in this section. Many can be rented for a one-time use from a local parts jobber or tool supply house specializing in automotive work.
Occasionally, the use of special tools is called for.Use Of Rtv And Anaerobic Sealer
Two types of sealer are commonly used in engines: Room Temperature Vulcanizing (RTV) sealer and anaerobic gasket eliminator sealer. The correct sealer must be used in the proper place to prevent oil leaks. Do not interchange the two types of sealers. Use the sealer recommended.Applying Anaerobic Sealer
- Anaerobic gasket eliminator hardens in the absence of air. This type of sealer is used where two rigid parts (such as castings) are assembled together. When two rigid parts are disassembled and you do not see any gasket or obvious sealer, the parts were probably originally assembled with an anaerobic gasket eliminator.
- Remove all gasket material from the part using a plastic or wood scraper. GM recommends Loctite® brand Gasket Remover P/N 4MA or equivalent. Follow all safety recommendations and directions that are on the container. Do not use any other method or technique to remove gasket material from a part. Do not use abrasive pads, since they leave a fine grit that will not filter out of the oil.
- Apply a continuous bead of gasket eliminator to one flange. Surfaces to be resealed must be clean and dry.
- Spread the sealer evenly with your finger to get a uniform coating on the sealing surface.
- Tighten bolts to specifications. Do not over tighten.
- Remove the excess sealer from the outside of the joint.
- Do not use RTV sealant in areas where extreme temperatures are expected. These areas include the exhaust manifold, head gasket and other areas where gasket eliminator is specified.
- Use a rubber mallet to separate components sealed with RTV. Bump the part sideways to shear the RTV sealer. Bumping should be done at bends or reinforced areas to prevent distortion of components. RTV is weaker in shear (lateral) strength than in tensile (vertical) strength.
- Remove all gasket material from the part using a plastic or wood scraper. GM recommends Loctite®brand Gasket Remover P/N 4MA or equivalent. Follow all safety recommendations and directions that are on the container. Do not use any other method or technique to remove gasket material from a part. Do not use abrasive pads, since they leave a fine grit that will not filter out of the oil.
- Apply RTV to a clean surface. Use the proper bead size, if specified. Do not allow sealer to run into blind threaded holes as it may prevent the bolt from seating properly or cause damage when the bolt is tightened.
- Assemble components while the RTV is still wet (within 3 minutes). Do not wait for the RTV to skin over.
- Tighten bolts to specifications. Do not over tighten.