BMW 3 Series 2.0d N47 (2009): Intake Repair, Air Leaks, Boost Pipes and Intake Manifold Gaskets

Part numbers are from the manufacturer's original catalogue. Check them against your VIN before ordering.

• Socket and wrench set
• Torx set (external and internal)
• torque wrench 5-25 N·m (4-18 lb-ft)
• pliers for hose clamps
• smoke machine or hand pump with pressure gauge for intake leak testing
• can of carburetor cleaner or foam sealant
• clean rags
• plugs to seal open ports

1. Read the engine fault codes and check the actual boost pressure. If it is lower than specified under load, suspect a leak downstream of the turbo. Remove the engine cover.
2. Inspect the air path: the turbo-to-intercooler pipe, the intercooler, and the intercooler-to-throttle pipe. Look for oil seepage, cracked rubber and loose clamps. An oily film at a joint indicates a leak.
3. Pressure test the intake at about 0.3-0.5 bar (4-7 psi) using a smoke machine or a hand pump with a gauge, with the inlet before the turbo plugged. The leak will show as smoke or can be heard. Do not exceed the specified pressure, to avoid damaging sensors and flaps.
4. If the leak is in the pipes, remove them. Disconnect the sensor connectors on the pipes, loosen the clamps or release the quick-release retainers. Replace the pipes and O-rings, and tighten the clamps moderately and evenly, without skewing (usually 3-5 N·m (27-44 lb-in)). Clean the mating surfaces of oil before installing.
5. If the leak is in the manifold area: disconnect the negative battery terminal. Remove the air duct to the throttle body, the pipe and, if necessary, the air filter and its housing. Disconnect the connectors of the boost pressure and temperature sensor, the throttle valve, the swirl flap actuator, and the vacuum and vent hoses.
6. Remove the exhaust gas recirculation (EGR) pipe and valve with the cooler if they block access. Cover the open ports with a clean cloth or plugs so that dirt and debris do not get into the cylinders.
7. Remove the intake manifold mounting bolts and carefully lift off the manifold. Do not drop any bolt or piece of gasket into the ports. Note the positions of bolts of different lengths.
8. Inspect the manifold: carbon and oil deposits inside are normal for a diesel and can be removed with cleaner. Check that the swirl flaps move freely and that the blanking plugs seal properly. If the flaps stick or the linkages break, replace the manifold as an assembly.
9. Clean the mating surfaces of the cylinder head and the manifold without scratching them. Install new gaskets (one per cylinder) in the correct position. Do not lubricate the seals unless the manufacturer specifies it.
10. Install the manifold and tighten the fasteners in two or three stages from the center outward. The torque for N47 manifold bolts is usually about 10-22 N·m (7-16 lb-ft); the exact value depends on the bolt and should be confirmed in the manufacturer's specifications. Install the pipes and connectors in reverse order.
11. Reconnect the battery, start the engine and check how it runs at idle. Repeat the pressure test or inspect the joints for smoke and oil seepage. Clear the fault codes and take a test drive under load, checking the boost pressure.

• Work on a cold engine and do not let any foreign objects get into the intake: even a small fragment entering a cylinder can lead to serious engine repairs
• On the N47, damage to or wear of the swirl flap actuator can cause the flaps to fall into the intake, so if there is play and a characteristic noise from the manifold in operation, assess its condition in advance
• If you have no experience disassembling engines, leave the job to a repair shop