I have a 97 318i 4 cyl 118k was running great for years drove about 8 miles to store no issues.. Got back in car 30 minutes later and cranked it up, sounds like a bad bearing squeal or grinding sound ,when rev. Engine sounds it's higher pitched.. Took both belts off and cranked up with no change help!!!!!
Water pump is belt driven so removing the belts will eliminate any water pump noise. Only other thing, is it possible that the starter is remaining engaged.
When that happens, it makes a lot of extra noise and it would be higher pitched as well.
Other than that, there is your throw out bearing if you have a standard. Push lightly on the clutch to see if pitch changes.
Timing chain issues like guides etc I don't think would make a high pitched sound. Also if something skipped a cog, the engine would run differently.
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