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

Exhaust Manifold

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REMOVAL & INSTALLATION M20 Engine



  1. Disconnect the negative battery terminal.
  2.  
  3. With the exhaust system cool, disconnect the exhaust pipes from the manifolds. Remove the 3 nuts on each flange connection and lower the exhaust pipes. Support the exhaust system. Make sure the oxygen sensor wire is not being stretched.
  4.  
  5. Remove the nuts securing the manifolds to the cylinder head. Remove the manifolds.
  6.  

To install:
  1. Clean the mounting surfaces on the manifolds and the cylinder head. Check the condition of the studs and replace if necessary.
  2.  
  3. Install the new exhaust manifold heat shield gaskets and install the manifolds. Torque the nuts to 16-18 ft. lbs. (22-25 Nm). Use new copper nuts.
  4.  
  5. Connect the exhaust pipes to the manifolds using new gaskets. Connect the negative battery terminal. Start engine and check for leaks.
  6.  

M30 Engine

  1. Disconnect the negative battery terminal.
  2.  
  3. With the exhaust system cool, disconnect the exhaust pipes from the manifolds. Remove the 2 nuts on each flange connection and lower the exhaust pipes. Support the exhaust system. Make sure the oxygen sensor wire is not being stretched.
  4.  
  5. Remove the nuts securing the manifolds to the cylinder head. Remove the manifolds.
  6.  

To install:
  1. Clean the mounting surfaces on the manifolds and the cylinder head. Check the condition of the studs and replace if necessary.
  2.  
  3. Install the new exhaust manifold heat shield gaskets and install the manifolds. Torque the nuts to 16-18 ft. lbs. (22-25 Nm). Use new copper nuts.
  4.  
  5. Connect the exhaust pipes to the manifolds. Connect the negative battery terminal. Start engine and check for leaks.
  6.  

M42 Engine See Figures 1 and 2

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Fig. Fig. 1: Remove these bolts when removing the exhaust manifold engine



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Fig. Fig. 2: Make sure the graphite side of the exhaust manifold gasket faces the cylinder head

  1. Disconnect the negative battery terminal.
  2.  
  3. With the exhaust system cool, disconnect the exhaust pipe from the manifold. Remove the 4 nuts on the flange connection and lower the exhaust pipes. Support the exhaust system. Make sure the oxygen sensor wire is not being stretched.
  4.  
  5. Remove the nuts securing the manifold to the cylinder head. Remove the manifolds.
  6.  

To install:
  1. Clean the mounting surfaces on the manifolds and the cylinder head. Check the condition of the studs and replace if necessary.
  2.  
  3. Install the new exhaust manifold gaskets with the graphite side towards the cylinder head and install the manifolds. Torque the nuts to 16-18 ft. lbs. (22-25 Nm). Use new nuts and anti-seize.
  4.  
  5. Connect the exhaust pipe to the manifolds. Connect the negative battery terminal. Start engine and check for leaks.
  6.  

M50 Engine

  1. Disconnect the negative battery terminal.
  2.  
  3. With the exhaust system cool, disconnect the exhaust pipe from the manifold. Remove the 3 nuts on each flange connection and lower the exhaust pipes. Support the exhaust system. Make sure the oxygen sensor wire is not being stretched.
  4.  
  5. Remove the nuts securing the manifold to the cylinder head. Remove the manifolds.
  6.  

To install:
  1. Clean the mounting surfaces on the manifolds and the cylinder head. Check the condition of the studs and replace if necessary.
  2.  
  3. Install the new exhaust manifold gaskets with the graphite side towards the cylinder head and install the manifolds. Torque the nuts to 16-18 ft. lbs. (22-25 Nm). Use new nuts and anti-seize.
  4.  
  5. Connect the exhaust pipe to the manifolds. Connect the negative battery terminal. Start engine and check for leaks.
  6.  

S14 Engine

  1. Disconnect the negative battery cable. With the engine cool, remove the coolant drain plug from the block. Remove the 2 electrical connectors from the front of the coolant manifold that runs along the exhaust side of the engine. Disconnect the radiator hose from the front of this pipe. Then, remove all the mounting bolts for this pipe and remove it. Inspect the O-rings and replace any that are worn or damaged.
  2.  
  3. Disconnect the exhaust pipe at the manifold flange. Remove the heat shields from under the engine.
  4.  
  5. Remove the mounting nuts at the cylinder head and remove the manifold.
  6.  
  7. Clean all gasket material from the surfaces of the manifold and head and replace the gaskets.
  8.  

To install:
  1. To install, position the manifold on the head, torquing the manifold bolts to 6.5-7.0 ft. lbs. (9 Nm) and the coolant pipe mounting bolts to 7.5-8.5 ft. lbs. (11 Nm). Torque the bolts at the flange attaching manifold and exhaust pipe first to 22-25 ft. lbs. (30-34 Nm) and then to 36-40 ft. lbs. (48-54 Nm). Make sure to refill the cooling system with fresh anti-freeze/water mix and bleed the cooling system.
  2.  

S38 Engines See Figures 3, 4 and 5

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Fig. Fig. 3: Removing the air injection pipe on the S38 engine



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Fig. Fig. 4: Exhaust manifold mounting locations on the S38 engine



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Fig. Fig. 5: To remove the manifold halves, pull outwards then apart on the S38 engine

  1. Disconnect the negative battery cable. Remove the exhaust system. Drain the coolant below the level of the head. Disconnect the right side engine mount and ground strap.
  2.  
  3. Disconnect the air injection pipe and the heat shield. Remove the fan cowl and coolant expansion tank. Remove the air pump air filter housing.
  4.  
  5. Lift the right side of the engine as far as possible without damaging any connections.
  6.  
  7. Remove the heat shield holder and the air injection pipe. It may be necessary to use an universal joint on an extension. There is a mounting tab at cylinder number 1.
  8.  
  9. Disconnect the sensor plugs on the coolant pipe. Remove the coolant pipe.
  10.  
  11. Remove the exhaust manifold nuts and pull of the studs. Push the rear manifold back and pull the front manifold. Remove the rear manifold.
  12.  

To install:
  1. Clean the manifold mounting surfaces of the manifold and cylinder head. Install new gaskets with the graphite surface towards the cylinder head.
  2.  
  3. Install the manifolds. Place the manifolds in the reverse order of removal. Torque the nuts 6.5-8.0 ft. lbs. (9-11 Nm).
  4.  
  5. Replace the O-rings and install the coolant pipe. Torque to 8.0-8.5 ft. lbs. (11-12 Nm). Replace the air injection pipe gaskets and the air injection pipe. Torque to 25-33 ft. lbs. (35-45 Nm).
  6.  
  7. Install the heat shield. Lower the engine. Install the air pump filter, coolant expansion tank and the fan cowl. Connect the air injection pipe and tighten to 25-33 ft. lbs. (35-45 Nm). Install the heat shield holder.
  8.  
  9. Connect the ground strap and the engine mount. Torque to 30 ft. lbs. (42 Nm). Install the exhaust system and fill the cooling system. Connect the negative battery terminal.
  10.  

 
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