Loud Noise Help!

[DForce909]

Hey Yall,

I need some help figuring out what is the source of a loud noise coming from my engine. To give a short background, my truck (daily driver) has sat for almost 4 months. I was gone on a deployment and got back a couple days ago. I noticed that whenever I hit the accelerator there is a loud noise that gets faster as I hit the accelerator and accelerate. I figured it had to be a pulley or the belt, but the belt is fine from what I know. No cracks or anything like that. I replaced the tensioner and idler pulley but have had no change in the sound. I even had a spare belt I keep just in case and changed it to that but the sound persists. Then I out some belt lubricant stuff since I thought maybe the dust and grime build up of just sitting has caused the noise, it helped for only a short time and the noise came back. I took the belt off and revved it and I have no noise coming from the truck, so it has to be a pulley or the belt. I also spun each pulley without the belt and didnt hear anything. Need some help figuring this out cause im at a loss. Its a 1997 chevy silverado c1500 5.7 V8. Any advice would be great as to where I need to turn to next. Thanks

 

[df2x4]

Did any of the accessory pulleys feel weird when you spun them? Anything that felt like resistance from a dying bearing? The fact that it doesn't make the noise with the belt off makes me think it has to be accessory related.

 

[df2x4]

If you can't feel anything strange, I'd run the truck with the belt on and check the accessories individually with a mechanic's stethoscope. Something like this.

https://www.amazon.com/Lisle-52750-Stethoscope-Kit/dp/B0015DLMOO

It's exactly what it looks like, you just put the probe end up against a solid surface. When you find the accessory that's to blame for your noise it'll be much louder than the others.

I accomplished basically the same thing by jamming a long plastic handled screwdriver through the bottom of a red Solo cup and taping it into place, it helped me diagnose a failing pulley on my Suburban's alternator. Beware that this method may only work for the stuff on top as you can't really squeeze your head and a Solo cup Rube Goldberg contraption down behind the radiator support.

Be careful with either method, don't get something stuck in the belt or around a pulley while the truck is running and you're testing.

 

[Pinger]

Might be worth checking the front pulley on the crank for snugness as well as the above.

 

[Schurkey]

Rock caught in the grooves of a pulley--or the belt?

Damaged accessory. You'd pretty-much have to check each one separately. Using the stethoscope as mentioned above is a fine idea.

A long wood dowel works OK, too.

I've seen A/C compressors, AIR pumps, PS pumps, idler pulleys, tensioner pulleys, and alternators make noise. I've removed damaged water pumps, but I don't remember them being noisy. Sure is possible, though.

Any belt you've sprayed with "belt dressing" you might as well toss. "Belt dressing" is a product that shouldn't be sold. They quiet the belt, but they don't make it stop slipping--they just lubricate it so it isn't noisy (for awhile). And the chemicals in the belt dressing may cause rubber to deteriorate, too.

 

[DForce909]

Thanks yall for the tips, I am going to see what I can find with what yall told me. Thank you!

 

[RichLo]

All of the above is great advice,

Another thing you could try as using some non-silicone lubricant like WD-40 and spray a small amount into the bearing area of each accessory. When the noise goes away you've found the culprit. I assume thats what happened with your belt dressing, a little got into the bad bearing for a short time.

 

[Schurkey]

WD-40 is NOT a lubricant. It's pretty terrible at just about everything except displacing water--from a wet distributor cap, for example.

WD-40 sells all sorts of chemicals under the WD-40 "Specialist" brand name, and some of them work quite well. But the WD-40 PRODUCT (not brand name) is damn near worthless.

https://www.wd40.com/#

The bearings on just about all the accessories are going to be sealed. The lube won't get in to do any good unless the seal is damaged.

 

[R422b]

Rock caught in the grooves of a pulley--or the belt?

Damaged accessory. You'd pretty-much have to check each one separately. Using the stethoscope as mentioned above is a fine idea.

A long wood dowel works OK, too.

I've seen A/C compressors, AIR pumps, PS pumps, idler pulleys, tensioner pulleys, and alternators make noise. I've removed damaged water pumps, but I don't remember them being noisy. Sure is possible, though.

Any belt you've sprayed with "belt dressing" you might as well toss. "Belt dressing" is a product that shouldn't be sold. They quiet the belt, but they don't make it stop slipping--they just lubricate it so it isn't noisy (for awhile). And the chemicals in the belt dressing may cause rubber to deteriorate, too.

I remember reading a document from a major belt manufacturer and it explained that one of the leading causes of belt failure is belt dressing.

Talking about GMT400s using Tapatalk

 

[RichLo]

WD-40 is NOT a lubricant. It's pretty terrible at just about everything except displacing water--from a wet distributor cap, for example.

WD-40 sells all sorts of chemicals under the WD-40 "Specialist" brand name, and some of them work quite well. But the WD-40 PRODUCT (not brand name) is damn near worthless.

https://www.wd40.com/#

The bearings on just about all the accessories are going to be sealed. The lube won't get in to do any good unless the seal is damaged.

I understand WD40's purpose in life and that too many people dont understand what you explained.

I just said WD40 because I didnt want him spraying a REAL lubricant right next to his belt where it would probably saturate the belt and cause it to slip and fail.

And the noise went away when he applied belt dressing... so WD40 or any other non-lubricant should quiet it down with a direct squirt to it.