BELT TENSIONER, IDLER, ? CHATTER

[bldn10]

'02 5.3 Tahoe 2WD. I have a chatter or rattle that started very subtle and is getting progressively louder and more frequent. It sounds from the seat like it is in the right front but I do not think it is suspension. It only does it when there is a load on the engine, when it is accelerating. It makes no difference if the A/C is on or off. FWIW I previously replaced the A/C tensioner and subsequently the compressor. Any ideas/suggestions?

 

[corvette744]

Sounds like a tensioner-i would take both belts off and spin and push and pull on everything see if its noticeable.

 

[retiredsparky]

If you still can't find, an automotive stethoscope is a handy, cheap tool to help hear how the various bearings sound internally. You don't place it against anything moving, just adjacent to the idler, pulley, etc.

Also, a digital thermometer can show the running temp. Old bearings heat up as they lose their lube and smoothness.

Fan clutches, harmonic balancers, water pumps, alternators are other sources of weird noises.

 

[M1Gunner]

Also since the compressor was replaced the transmission lines may have been disturbed. Make sure they are properly secured and clear of other components. Also double check the heat shields on the catalytic converters. They may look fine but tap on top especially the passenger side converter. All it takes is one small bead to break. An engine under load will cause the these two things vibrate/chatter at just the right frequency. Food for thought.

 

[OR VietVet]

If it will make the noise sitting still you can remove the belt(s) and accel and see if noise is still there or get to an area where you can start and accel from a stop, with the belt off, and not be in traffic, like a large parking lot. I agree with checking the exhaust shields and all engine/exhaust mounts areas. The recommendation about the mechanic's stethoscope, by retiredsparky, is a great one. I have one and is a fantastic tool in my arsenal for tracking down noises. Inexpensive and a must have. In case you are interested, other must have time savers are a collection of 3-4 different gauges of wire in assorted lengths with alligator clips on the ends, your own cheap code retrieval tool, digital volt/ohm meter-cheap and if you don't have a dedicated bolt and nut drawer in your tool box you will be kicked out of the tech society. Almost forgot, an assortment of nice picks with different ends. Still have my Snap-On set I bought over 30 years ago.

 

[bldn10]

Thanks for all the suggestions. I haven't had a chance to try anything yet but will tomorrow. To clarify, it DOES NOT do it sitting still, it does not even do it driving when off throttle. FWIW I also recently had the rear main seal replaced - don't know what they had to take off to do that. It would be nice if I could put it on them.

 

[M1Gunner]

[QUOTE="It would be nice if I could put it on them. [/QUOTE]

Just pullin the tranny. To access the rear main. If they would’ve left a torque converter bolt loose it you would make the noise even at a sit still. They also pull the y-pipe to remove the tranny. So it could very well be a transmission line that wasn’t secured properly vibrating on something at a certain rpm or the heat shield of the pass side cat doin the same thing.

 

[OR VietVet]

Yea, something left loose or dangling after trans reinstall.

 

[1_8TTony]

Dip stick tube rattling against the firewall???? The 13mm nut which secures the tube is difficult to get to......maybe the shop tech's were too lazy to secure the tube.

Or...

Broken a/c belt tensioner???? I've replaced some broken ones over the years due to cracked spring housings.

Broken sheet metal due to fatigue located at the front tip of the fender where the fender underlaps the hood and bolts onto the radiator core support???

Or...

Broken tab on the face of the a/c clutch.

 

[bldn10]

Would it be the A/C tensioner if it does it even when the A/C is not on?

 

[M1Gunner]

Would it be the A/C tensioner if it does it even when the A/C is not on?

Maybe if it was rode hard and put up wet and 20 yrs old... but I don’t believe that’s gonna be your problem.

 

[OR VietVet]

Yes, it could be. Sometimes the noise made by that can go away just by turning on the a/c because of the increased load on the belt and tensioner and then the noise dynamic is changed and cannot be heard as easily, if at all.

 

[Doubeleive]

make it simple, crawl under the vehicle take a 3/8 drive ratchet and stick it in the front of the a/c belt tensioner, pull the tensioner with the ratchet so you can remove the belt, start the vehicle if the noise is gone that's your problem, this will literally take you a couple minutes to do

 

[bldn10]

"To clarify, it DOES NOT do it sitting still, it does not even do it driving when off throttle."

 

[Doubeleive]

"To clarify, it DOES NOT do it sitting still, it does not even do it driving when off throttle."

did you take off the ac belt to see if the problem goes away?, the a/c belt tensioners are notorious which is why I think they eliminated them altogether now.

 

[bldn10]

And drive it?

 

[D is for DENALI]

Yes, that's why they put 2 belts in my opinion, so if the a.c. went put somehow you could cut the belt and still have a serp belt to drive on...

If the defroster is on, the ac kicks on at any temp, its trying to blow dry air...

I had that chatter and it was a bad compressor that wouldn't the noise under power, even stopped, just hit the pedal and I the increase in load would make it chatter... I replaced the compressor, orifice, accumulator, tensioner and pulley, and it went away... lolz but now I have air that's 38°...

 

[Doubeleive]

And drive it?

YES AND DRIVE IT, WONT HURT ANYTHING THE BELT CAN JUST HANG THERE.
I will clarify that, take off a/c belt only, not the serpentine belt

 

[bldn10]

I took off the A/C belt and the noise pretty much stopped. Tensioner, right? So I replaced the tensioner, put the belt back on, and . . . noise again. The problem is not the tensioner, it's the location of the compressor. I don't know how I missed this thread but post #27 explains it: http://www.tahoeyukonforum.com/threads/rattle-coming-from-engine-when-a-c-on.16386/page-3

Apparently another Chevy design mistake. The tensioner I took off was eaten away at the stop, where it had been banging back and forth. I've taken the belt back off so I don't have to listen to that noise and ruin another tensioner and maybe compressor until May.