BMW E46 finding an intake leak
E46 intake leak: where is it usually found?
The most common leak points are the throttle body and intake pipe bellows, which tear on the hidden side, and the vacuum hoses and their connections. On the M52TU engine, the plugs at the rear of the intake manifold can also become brittle and leak.
How do you locate an E46 intake leak?
1. Start the engine and let it idle. 2. Spray suspect spots with starting spray or brake cleaner. 3. When the spray is sucked in at the leak, the engine's running changes. Alternatively, you can blow compressed air into the intake system, and the leak can be heard.
How do you find a leaking vacuum hose?
A vacuum gauge shows whether vacuum is missing. Remove the hoses one at a time: the hose with no vacuum has a crack or is not connected to the intake manifold.
Why does an intake leak cause fault codes and why is the fault not fixed immediately?
The leak makes the mixture lean, and the engine control tries to correct it by enriching. When the correction is not enough, a mixture correction fault code is set. So the code alone does not mean the fault is in the oxygen sensor. If the car does not learn the new situation after the leak is fixed, reset the learned values by disconnecting the battery.