Checking the exhaust system for leaks (BMW 5 Series E39)

In vehicles with a regulated catalytic converter, a leak in the exhaust system before the oxygen sensor can cause the following problems:

• difficulties starting;
• engine loses crankshaft speed;
• vibrations are noticeable at idle;
• jolts during acceleration.

Prerequisite for checking: the engine is cold or warm to the touch.

Start the engine and, while the engine is running, plug the exhaust pipe with a rag or a plug. Together with an assistant, listen to the exhaust system for exhaust leaks (whistling noises, gas leaks can be felt by hand).

Spray the joints between the cylinder head and the exhaust manifold and the exhaust manifold/front exhaust pipe with standard Leck-Sucher leak detection agent and check for bubbles.

Eliminate the leak.