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Hi all--
My '89 745GL (128,000 mi) has been making quite a bit of (what sounds to me and my mechanic like) valve noise at idle. It's a high-pitched, sqeaky/chittering noise that happens when the engine surges during idle (i.e., the normal amount of RPM ebb and flow you get, the idle is as smooth as it's ever been and just as smooth as my old 745GL or my father's 945T). At first I thought the noise was belt-related, but after having the water pump replaced and the belts receiving a clean bill of health the noise is still there. I took a long stick and tried the "mechanic's stethescope" trick to isolate the noise, but got nothing on the head or manifold. The noise is loudest when I squat down next to the front passenger (right) fender.
I'm just wondering if this is anything to be concerned about. Hardened valve rings? Insufficient oil circulation? I change the oil between 3 and 4,000 miles, and am still using mineral. I tried some STP valve cleaning additive in a tank of gas with no change. I'm having zero problems otherwise, I just want to make sure I'm not building up to a catastrophic/expensive failure. Thanks!
jeff daigle
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