BMW 318/325/M3/525/535/M5 1989-1993 Repair Information

Intake Manifold

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REMOVAL & INSTALLATION M20 Engine



  1. Disconnect the battery ground cable and drain the cooling system.
  2.  


CAUTION
When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

  1. Disconnect the wire harness at the air flow sensor. Remove the air flow sensor as an assembly. Disconnect the air intake hose running from the air flow sensor to the manifold.
  2.  
  3. Remove and tag the vacuum hoses and electrical plugs. Disconnect the accelerator linkage (and cruise control linkage, if so-equipped) from the throttle housing. Disconnect the throttle position sensor harness.
  4.  
  5. Disconnect the coolant hoses from the throttle housing.
  6.  
  7. Working from the rear of the manifold, disconnect the vacuum lines and the electrical harness. Tag the connectors and lines for ease of assembly.
  8.  
  9. Disconnect the fuel injector electrical connections. Disconnect the injector harness loom from the manifold and pull out of the way.
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  11. Disconnect the fuel lines from the injector rail.
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  13. Disconnect the intake manifold support from the valve cover. Remove the nuts holding the intake manifold and remove the intake manifold.
  14.  

To install:
  1. Install the intake manifold with new gaskets and torque the nuts to 16-18 ft. lbs. (22-25 Nm). Install the support and torque to 15-17 ft. lbs. (20-24 Nm).
  2.  
  3. Install the fuel lines to the fuel rail. Install the injector harness loom and connect the fuel injector plugs.
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  5. Connect all lines, electrical connections and harness connections. Connect the coolant lines, the throttle position sensor and the throttle cables.
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  7. Connect the ducting from the air flow sensor to the throttle and the air flow sensor.
  8.  
  9. Fill the cooling system with coolant mixture and connect the negative battery terminal.
  10.  

M30 Engine

  1. Disconnect the battery ground cable and drain the cooling system.
  2.  


CAUTION
When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

  1. Disconnect the wire harness at the air flow sensor. Remove the air flow sensor as an assembly. Disconnect the air intake hose running from the air flow sensor to the manifold.
  2.  
  3. Remove and tag the vacuum hoses and electrical plugs. Disconnect the accelerator linkage (and cruise control linkage, if so-equipped) from the throttle housing. Disconnect the throttle position sensor harness.
  4.  
  5. Disconnect the coolant hoses from the throttle housing.
  6.  
  7. Working from the rear of the manifold, disconnect the vacuum lines and the electrical harness. Tag the connectors and lines for ease of assembly.
  8.  
  9. Disconnect the fuel injector electrical connections. Disconnect the injector harness loom from the manifold and pull out of the way.
  10.  
  11. Disconnect the fuel lines from the injector rail.
  12.  
  13. Disconnect the intake manifold support from the intake manifold at the bottom. Remove the nuts holding the intake manifold and remove the intake manifold.
  14.  

To install:
  1. Install the intake manifold with new gaskets and torque the nuts to 16-18 ft. lbs. (22-25 Nm). Install the support and torque to 15-17 ft. lbs. (20-24 Nm).
  2.  
  3. Install the fuel lines to the fuel rail. Install the injector harness loom and connect the fuel injector plugs.
  4.  
  5. Connect all lines, electrical connections and harness connections. Connect the coolant lines, the throttle position sensor and the throttle cables.
  6.  
  7. Connect the ducting from the air flow sensor to the throttle and the air flow sensor.
  8.  
  9. Fill the cooling system with coolant mixture and connect the negative battery terminal.
  10.  

M42 Engine See Figures 1 through 7

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Fig. Fig. 1: The rear brace and hose on the M42 engines intake manifold



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Fig. Fig. 2: Remove the this nut when removing the upper section of the M42 engines intake manifold



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Fig. Fig. 3: Remove the these bolts when removing the upper section of the M42 engines intake manifold



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Fig. Fig. 4: Lift off the upper section of the intake manifold and remove the vacuum hose engine



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Fig. Fig. 5: Replace the gasket and check the dowel sleeves before replacing the upper section of the intake manifold engine



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Fig. Fig. 6: Removing the injector rail-M42 engine



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Fig. Fig. 7: Remove these bolts to remove the lower intake manifold engine

  1. Disconnect the battery ground cable. Remove the air duct to the throttle body.
  2.  
  3. Disconnect the rear mounting bracket and remove the hose.
  4.  
  5. Loosen the front mounting bracket and remove the nut directly under the throttle body.
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  7. Remove the 9 mounting bolts and lift off the upper manifold section. Pull the hose off the fuel pressure regulator at the same time.
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  9. Pull the plug plate off the fuel injectors and remove the clamp.
  10.  
  11. Remove the injector rail with the fuel injectors attached. Remove the 5 bolts holding the lower manifold section and remove the manifold.
  12.  

To install:
  1. Check the sleeves on the studs. Replace the manifold gasket and install the lower manifold section. Torque to 10-12 ft. lbs. (13-17 Nm).
  2.  
  3. Lubricate the injector seals with a slight film of oil and install the injector rail. Install the plug plate and clamp.
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  5. Connect the fuel pressure regulator vacuum line and install the upper manifold section with a new gasket. Torque to 10-12 ft. lbs. (13-17 Nm).
  6.  
  7. Tighten the nut directly under the throttle body. It may be necessary to bend the tab against the throttle body.
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  9. Connect the front and rear braces. Connect the hose to manifold. Connect the air duct to the throttle body. Connect the negative battery terminal.
  10.  

M50 ENGINE
  1. Disconnect the negative battery cable and drain the coolant to a level below that of the throttle housing. Unscrew the fastener from the throttle cable cover and pull the cover forward and off. Unclip the cable and pull the cable out with the rubber holder.
  2.  
  3. Pull the vacuum fitting from the brake booster and plug the openings.
  4.  
  5. Remove the engine and intake manifold covers. Unscrew the bolt holding the ground strap on the front lifting eye. Replace the bolt before lifting the engine.
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  7. Unscrew the 2 bolts holding the plug plate and pull off the plug plate. Be careful not to damage the rubber seals. Take off the ignition coil electrical plugs. Remove the plug plate complete with the electrical leads.
  8.  
  9. Remove the cylinder head vent hose and pull off the air temperature sensor plug. Remove the tank venting hose and the throttle heating hoses from the throttle body. Remove the throttle valve switch plug. Unclip the hose mounted on the manifold for the idle speed control valve. Mark and disconnect the fuel hoses from the pipes near the throttle and disconnect from the pipe on the subframe.
  10.  
  11. Disconnect the manifold support braces. Unscrew the hardware holding the intake manifold to the cylinder head. Remove the intake manifold taking care not to drop anything into the exposed ports.
  12.  

To install:
  1. Inspect the intake manifold seals and replace. Install the intake manifold and torque to 14-17 ft. lbs. (20-24 Nm). Install the intake manifold supports.
  2.  
  3. Connect the fuel hoses near the throttle body and the subframe. The rear line is the return line and the front line is the feed.
  4.  
  5. Install the hose for the idle speed control by pushing it into the manifold. Connect the throttle switch plug and the throttle heating hoses. Connect the air temperature sensor.
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  7. Clip in the crankcase vent hose connector. Plug in the ignition coil harness connectors. Install the plug plate and the ground strap. Install the covers, brake booster vacuum line and the throttle cables.
  8.  
  9. Fill the cooling system with coolant, connect the air intake duct and the negative battery terminal.
  10.  

S14 Engine

A Torx nut driver is needed to perform this operation.

  1. Disconnect the negative battery cable. Remove the cap nuts at the outer ends of the 4 throttle necks. Then remove the mounting nuts underneath.
  2.  
  3. Make sure the engine has cooled off. Loosen the hose clamps for the air intake lines and for the fuel lines where they connect with the injector fuel rail. Collect fuel in a metal container.
  4.  
  5. Disconnect the throttle cable.
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  7. Pull off the intake manifold. Remove the crankcase ventilation hose running to it from the crankcase. Then, remove the manifold and place it aside. Use a new crankcase ventilation hose during installation.
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  9. Pull off the throttle valve switch plug.
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  11. Pull the fuel pressure regulator vacuum hose off the pressure regulator.
  12.  
  13. Remove the 2 mounting bolts for the injector pipe. Then, carefully lift off the pipe and injectors. Remove the clips holding the connectors to the injectors and pull the plug plate off the injectors.
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  15. Unscrew the nut attaching the ball joint at the end of the throttle actuating rod to the throttle linkage. Supply a new self-locking nut.
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  17. Remove the nuts attaching the throttle necks to the cylinder head. Then, remove the 4 throttle necks as an assembly.
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  19. Separate the throttle neck assemblies by pulling them apart at the connecting pipe.
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  21. Inspect the O-rings in the connecting pipe and at the outer ends of the throttle necks. Replace as necessary.
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  23. Reverse the removal procedure to install. Use the new throttle linkage self-locking nut and the new crankcase ventilation hose.
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  25. Torque the nuts attaching the throttle necks to the head and the intake manifold to the throttle necks to 6.5-8.0 ft. lbs. (9-11 Nm). Adjust the throttle cable.
  26.  

S38 Engine

  1. Disconnect the negative battery terminal. Disconnect the throttle cable. Remove the air intake hose. Remove the screws on each throttle valve assembly.
  2.  
  3. Disconnect the hose for the idle speed control, the venting hose and the oil return hose. Remove the nuts for the oil trap and pull off the air intake assembly.
  4.  
  5. Pull off the plug plate from the fuel injectors. Disconnect the fuel lines from the fuel rail. Pull of the intermediate plug for the idle speed control. Remove the fuel rail with the fuel injectors.
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  7. Disconnect the vacuum hoses after noting the routing. Remove the 6 10mm nuts and the 9 13mm nuts. Remove the shaft connection nut. Disconnect the throttle linkage and remove the throttle bodies.
  8.  
  9. Separate the throttle bodies by disconnecting the connecting pipes. Check the O-rings on the pipe. Clean the throttle shafts before pulling out of the bores and do not use tools on the shaft or it may be damaged.
  10.  

To install:
  1. Install the throttle bodies together using new O-rings on the connecting pipes. Install the throttle bodies on the engine using new gaskets. Tighten the 10mm nuts to 6.5-8.0 ft. lbs. (9-11 Nm) and the 13mm nuts to 14-17 ft. lbs. (20-24 Nm).
  2.  
  3. Route and connect the vacuum hoses. Install the shaft connection nut and the throttle linkage. Install the fuel rail and the fuel connections. Connect the intermediate plug and the injector plug plate.
  4.  
  5. Check the O-rings on the air intake assembly and attach the pins at the bottom of the assembly. Install the air intake assembly.
  6.  
  7. Connect the oil return hose, the idle speed hose and the venting hose. Install the air intake duct and install the screws at each throttle. Connect the negative battery terminal.
  8.  

 
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