Hi there. I am the (normally) very happy owner of a 1991 Alpine White E34 M5. This is my first post on this Board. I need some help eliminating a very annoying noise. It is a whistling noise. Starts when the car is just starting to warm up. The engine has probably only been running five minutes or less. The whistle is not present when the car is idling. It comes on at about 1400 rpm and continues up to about 2200 rpm when it is lost in the general engine noise. It gets higher in pitch as the rpms increase. It is louder when the engine is hot.

First thought was a vacuum hose. All have been checked and seem fine. Any suspect one was replaced. Next thought was the alternator or something being run by one of the belts up front. All belts were removed and the engine run (briefly). The noise was still there. Starter fluid has been sprayed on the connectors from the throttle bodies to the intake manifold (looking for a funny idle problem) but there was no sign of any leak there.

Then my mechanic (Bavarian Professionals in Berkeley) traced the noise with a sophisticated stethoscope which allows you to home in on one frequency. The noise seemed o be coming from behind the harmonic balancer. They removed the front crank seal. There was a groove being worn in the crank seal cover so that was ground out, everything was lubed up, a new gasket installed and put back together. The noise was still there.

Next I replaced the cam chain tensioner with the newer version from the E36 M3. No change in the noise. Recently we have dropped the oil pan and replaced the oil pump. They inspected the oil pump drive chain and sprockets and there was no sign of unusual wear or anything. No change in the noise.

The cheap solution would of course be to buy earplugs, but then I wouldn't be able to hear that wonderful roar of the engine. Has anyone had a similar problem? Were you able to fix it? How? Anyone have any suggestions?