BMW E32 intake air leak and intake manifold gaskets
Why do the E32 intake manifold gaskets leak?
On the M70 engine the weight of the intake manifold and throttle body housing rests on the gaskets, so they harden and leak. The original gaskets almost always leak. New rubber pads support the weight. A car that has stood for a long time dries out the gaskets even more.
How do I find an intake air leak on an E32?
With the engine running, the leak can be found by spraying starter spray at the suspected spots: the revs change at the leak. The leak can also be in a vacuum or breather hose, which are worth checking and replacing at the same time. On the M30, all the vacuum hoses must be in good condition.
Is an uneven idle on an E32 always an intake air leak?
No. An intake air leak is one possible cause, but a hunting idle can also be caused by the distributor cap or a partly loose crankshaft sensor. Rule out the intake air leak first and go through the sensors one by one if needed.