1998 Buick LeSabre -- constant loud whirring noise (loudest when starting)

1998 Buick LeSabre with about 60,000 miles on it … for the last 6 weeks there has been a constant whirring sound that is loudest right after ignition. When hitting the accelerator, it volume goes up, too. Initially thought it might be a belt but it’s not. My mechanic suggests it could be the alternator.

Thoughts on this? Advice? I figure that the low mileage (I bought three years ago at 35,000 miles) makes it worthwhile to pay for the fix. Also not sure how long it’s OK to keep running it with that noise.

Had the intake gasket replaced in February.

Remove the belt and start the engine. You can let it run for a few minutes if needed. If the sound isn’t there then the problem is likely the alternator or one of the other accessories run off the belt. If the noise continues closely inspect the intake plenum and throttle body for vacuum leaks.

I’m going to suggest using a mechanic’s stethoscope (about $10). Put the listening piece in your ears, and put the tail on the item that you are suspecting (be sure not to get whacked by the belt!). I had a similar sound in my 1993 Jeep and I diagnosed it this way. The grinding was very loud when I touched the power steering pump. Changed that, all good.

JP

A length of old garden hose can work as a sound locating stethoscope too. As well, a long screwdriver, carefully position the tip on the alternator case and listen at the end of the handle. Might be able to isolate where the whirring noise is coming from. Just by the description I lean toward the mechanic, “alternator” is the primary suspect.