Cummins Diesel Forum banner

Horrible squeal coming from around the belt.

3K views 17 replies 7 participants last post by  CTK30 
#1 ·
I thought it was the belt, so I put dressing on it. Worked for like 10 minutes.

I can't pinpoint where it's coming from, it almost sounds like bearings or something.

The AC compressor kicks on and off and the noise really doesn't change that much.

I'm guessing either the alternator or tensioner.

I know you can't see it from your house, but any tips I can use to narrow it down?

TIA.
 
#2 ·
pull the belt and see if the water pump spins ok

also could be the tensioner, i had one go out on my 3500 before, bearing was shot
 
#5 ·
Water pump is working good, it's a brand new Cummins unit, less than 4 months old.

I'm leaning towards the tensioner. It's moving a little bit and the sound seems to go along with its movement.

Get a piece of heater hose (something hard works better like a pry bar or long screwdriver, the more rigid/less rubber or wood in the handle the better, put it to your ear and put other end to the alternator/tensioner/any other pulleys you suspect. Napa may even sell a stethoscope setup with a lil metal rod on the end (made for this kind of diagnosis). I've had alternators do this before. Never noticed it in a tensioner without movement of some sort in the pulley. May also be the spring squeaking in the tensioner if it's about to go. With the truck running watch the tensioner and see how much "bounce" it has. Just some ideas.
Thanks bud, I'll check it out.
 
#3 ·
Get a piece of heater hose (something hard works better like a pry bar or long screwdriver, the more rigid/less rubber or wood in the handle the better, put it to your ear and put other end to the alternator/tensioner/any other pulleys you suspect. Napa may even sell a stethoscope setup with a lil metal rod on the end (made for this kind of diagnosis). I've had alternators do this before. Never noticed it in a tensioner without movement of some sort in the pulley. May also be the spring squeaking in the tensioner if it's about to go. With the truck running watch the tensioner and see how much "bounce" it has. Just some ideas.
 
#4 ·
I dont think my tensioner was bouncing with the belt on it, but when I removed the belt the pulley was super loose and loud.
 
#6 ·
The water pump being new: I replace tensioner with wp's whenever possible as they seem to go together. I had the wp go out on my 01 and 1 week later tensioner spring broke.
 
#7 ·
It's probably the tensioner.

I sprayed it with WD40 and it went away for a little - I'm guessing alternator or tensioner.

Hope it's not the AC compressor.
 
#8 ·
#9 ·
Just me, but I wouldn't pour water on my engine. I would take the belt off and turn the pulleys and see if I could repeat the squeal. If I was going to throw parts at it, I'd start with the tensioner. Cheap(er) and easier to replace.
 
#10 ·
Why wouldnt you "dump" water on a 12 valve? What are you going to break? I agree I wouldnt do it to troubleshoot this problem, but its fine to dump water on an engine. Unless interpreted what you said wrong.

Hell ive sprayed down the engines on every vehicle i have ever owned to degrease them and have never had an issue. Obviously dont soak the alternator but thats common sense
 
#11 ·
Take a screwdriver a long one and press the tip against the tensioner and then the alternator and stick your ear against the other one, you'll be able to hear if it is either one through the screwdriver.
 
#13 ·
Put a new belt on it and it fixed the noise.

Everything checked out ok under the hood.
 
#16 ·
In the future:
The way I check for belt driven failing bearing noise is to use a hand squeeze water sprayer and wet the bearing area with the engine running.
When you hit the right spot the sound changes or goes away for few seconds.
 
#17 ·
Thanks for the tip, bud.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top