Hi everyone, this is my first post. I have a 99 Bonneville SE, nice car, good condition, black with tan leather interior, 116,000 miles. My problem started about 2 months ago, the engine started making a strange noise sounded like a tensioner pulley had a bad bearing. I replaced it and the noise remained. It sounds like it is comming from the front (belt side) of the engine. I took the belt off and spun the alt. (wasn't charging consistant anyway) sounded like it was a little dry as well, replaced it. Noise still there. I then replaced the powersteering pump. Noise still there. Took the belt off, started the car and it still made the squealing noise like a slipping belt. Asked a local mechanic and he said move the belt and watch the harmonic balancer if it moves at all it needs replacing. Tried the belt, outer ring moved, replaced the balancer. Never guess, noise still there. The noise will remain as long as the car is running, shut the car off and give it about 30 seconds and restart it and no noise for about 15-30 seconds, then sqeels like a pig. I have driven about 4500 miles since this started (I have a long commute to work) noise still there, no visible material in the oil, (metal or plastic). I was thinking something in the timing chain and tensioner, possibly a plugged oiling hole. The car still runs great, good mileage, good power. Any suggestions? Thanks!!!

Check the PCV, it'* at that end and if BOTH o rings aren't properly in place, it'll whistle. Whislte vs sqeal...well...at this point you sound desperate.

The next thing I'd check is take a picture of the marks on the tensioner while the belt is on. It might be weak and letting the belt slip. Last thing would be ...try a new belt if that one is old.

I agree with Bill on the PCV problem, especially as the problem is still there with the belt off.

With the belt off, it still squeals. That certainly limits the possibilities. Like Boosty said, could be PCV whistle. But if it is squealing like a slipping belt, without the belt- the only things moving on that end of the engine would be the HB, the timing chain, oil pump and cam. Could something be bent and rubbing or jammed against the HB? Maybe a piece of debris (like an old interrupter magnet) got jammed against a rotating shaft? Never heard of a noisy oil pump, or a squealing timing chain. Please let us know what it was when you figure this one out.

Did you replace ALL tensioners/idler pulleys? I had a very loud sqealing/sqeaking idle. Of the 4 tensioners/idlers, two were bad.

Psst Pete..squeals w/o belt. (don't make me point out my goof up above..ok?)

Did the squealing/whistling start when/if you replaced the serpentine belt?

I had the exact same issue on my 99. I let it go for about year and finally this past March we had a nice day and I had the windows. It was driving me NUTS so I replaced the serpentine belt. No more squeal.

The noise originated some 40,000 miles ago when I replaced the factory belt with a GatorBack. The GatorBacks are very noisy and cause a whistle.

WIth the engine running, take the oil cap off. Does it try to suck your t-shirt into the engine? Does the noise stop?

I have noticed that there seemed to be a large amount of vacuum in the crankcase before. I tried the removal of the oil cap while the engine was running and making the noise, as soon as I broke the vacuum seal, the noise quit, I them replaced the cap and the noise came back but it took a while. I tried it again and the noise quit. Now what can I do to lessen the crankcase vacuum to get the best of both worlds. I had replaced the pcv valve when I did the plenum replacement, but I put nearly 8,000 miles on the car before the noise started.

Thanks to everyone who responded!

I have several more gray hairs trying to figure this out and worring about the catastophic engine failure that I was sure was going to happen at the most inoppertune time. Now to explain to my wife how I spent close to $600 chasing down problem that now looks to be very minor.

Best not to tell the wife.

Who’* post was it that had the good pictures showing how to check the o-rings?


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