Wierd noise

paintguy · January 20, 2005

'89 Chevy Van 350 TBI:

This noise has been getting worse in the past 6 months. It is worse now with the frigid temperatures. The noise gets worse or better with engine rpm. It sounds like a mix between a fairly loud humming noise and a whistling noise. I used to spray Prolong lubricant on the upper serp belt tensioner and the alt and a/c pullies and it would subsied, but that has stopped working. I think it could be a pulley or the serp belt tensioner? Someone metioned it may be a cracked pully (but you know vans, they are so easy to see the front end under the hood!!!) Also I am thinking it could be the alternator bearings? The alt. works fine as in recharging the battery.

Does anyone have any idea what this noise may be seeing that it stops and starts depending (inconsistently) on engine rpm?

Also, when it is idling (it idles really nice), it sort of comes and goes.

I was originally thinking it might be a vacuum leak, but it just seems to loud and I had checked that when it originally started happening..

Any thoughts would be greatly appreciated.

Brandon

Wingnut · January 20, 2005

Really...It could be any/all of the above.

If it only does it on wet/humid days, I would lean more towards the belt being bad.

But the pulleys on these things aren't the best quality and will go bad, but if it's the idler pulley (I'm not sure if the 89 even has one), it will probably shuck the belt off. I would lean more towards the tensioner pulley on that one.

On my 5.7 TBI, the alternator bearings have gone out at least 3 times. Then I had a speed shop rebuild mine to 185 amps with some higher quality parts. Havn't had a problem since.

Welcome to the forums by the way

paintguy · January 25, 2005

Thanks for the reply Wingnut. It stopped doing it again after a good dosing of Prolong -- I know that is not the answer, and the next time it happens I will investigate it more fully so I don't have a breakdown. It has been so d**n cold here in upstate NY lately, so I haven't taken the time to properly diagnose. I will repost if it happens again and I find the prob.

Thanks again.

Brandon

paintguy · February 17, 2005

It wound up being the tensioner pulley making the funny noise -- I found out when it broke off and I lost the serp. belt. It probably was cracked for a while and that is what was making the wierd noise -- the air hitting the crack, therefor the noise changed with engine speed/rpm. It was the original tensioner pulley that had 190k miles on it! Unfortunately, it was a saturday afternoon when it happened and GM was not open and I needed to get it back on the road, so I had to use the cheapo one from autozone. Good thing is that the belt was fairly new and it was not damaged -- bought a new pulley, installed it roadside, and was good to go!

Thanks WINGNUT for your imput.

Brandon