Loud squeal when reved


#1

I’ve been working on a 04 Buick rendezvous and it has a very loud high pitch squeal when revved past 3000 rpms. Along with a serious power loss when the squeal starts. Has a new power steering pump as of today. And I took the belts off and reved it and the squeal is still there. That rules out the squeal coming from the belts. It is coming from some where in the engine bay and I’m stumped. I was almost positive it was the power steering pump since it sounded like it was about to go. But alas it was not. I does a little squeak when first started but nothing when ideling. Any ideas? I’ve heard of a squeal coming from a clogged cat and it blowing out the egr valve. The squeal is so loud that you can hardley stand near the car.


#2

Have you checked if the harmonic balancer on the crankshaft is worn out?

Tester


#3

How do you check? I tried spining it by hand and there is no play in it. It doesn’t budge. as it shouldn’t be easy to turn


#4

Could also be the tensioner pulley on the timing belt or could be a water pump if it is not driveb by a serpentine belt.


#5

Your plugged exhaust idea has merit…Remove the forward 02 sensor and check for excessive back-pressure at that point…


#6

One question…why would you ever rev an engine over 3000 rpm unless you were on a race track? Just curious.


#7

? I believe your car gets above 3000 rpm daily when driving through traffic. Getting on the interstateinterstate. Just going through the gears? Why would it not


#8

Sitting still and driving are two completely different things. Are you sitting still or driving above 3000 rpm? Revving an engine usually means that the engine is running and the transmission is in neutral. It’s not good for the engine to rev over 3000 rpm when it’s not going anywhere. Like I said…just curious.


#9

Whether in neutral or drive. Only reason I was reving it in park was to replicate the sound. Come to the conclusion its most likely a bad bearing in the engine.


#10

V6-3.6L has multiple timing chains and tensioners. Hold a piece of hose against the timing cover and your ear should narrow it down.


#11
...it has a very loud high pitch squeal when revved past 3000 rpms. Along with a serious power loss when the squeal starts.

Wild guess: vacuum leak inside the brake booster.


#12

I don’t know, but one time I had an early 60’s Ford w/a V6 and it would whistle like a tea pot. Not a little whistle, really loud. That turned out to be the valve cover has worked loose.

If it is something like that, it would have to be explained by a condition where some pressure changed during high revs. The intake pressure is usually low at high revs. So that would tend to point to the exhaust.

A length of garden hose can sometimes be used as a stethoscope to narrow down the location. Best of luck.

Edit: Another idea, water pump. If it is driven by the timing belt.


#13

Does this vehicle have the 3.4 or the 3.6 engine?


#14

FWIW, I think Tester is on the right track when he suggested the harmonic balancer might be the problem. When you removed the engine belt and still heard the squeal, the harmonic balancer would be my chief suspect. Both V-6 engine options on that Buick use timing chains and thus those would seem unlikely to cause a squealing sound. When you used hand power to inspect the harmonic balancer, it might not have been loose enough to be moved by hand. After all, you rev it past 3000 rpm to make the sound. That’s a lot of force. You can make a match mark on the inner and outer part of the balancer to see if there is any movement after revving the engine a bit and getting it to squeal. The balancer can also fail by wobbling or by the outer portion walking forward or backward relative to the inner portion.

By coincidence two weeks ago I replaced a harmonic balancer on a Pontiac Montana with a 3.4 engine. This one was wobbling slightly but did not produce squealing noise at the time. It wasn’t too difficult aside from being a bit tight when pulling it off. The new one going on was much easier. I used a puller to remove it and an installer tool to replace it. I did have to buy shorter (2" long) puller bolts to accommodate the limited room but I didn’t have to lower the subframe. BTW, although the center crank bolt is a metric 15mm hex, the tapped holes on the balancer use standard 3/8" x 16 UNC bolts (9/16" hex).