AC Adjuster Pulley

budhayes3 · October 21, 2004

I've noticed a couple of threads about noise when the ac compressor engages, normally you would think that the compressor is on it's way out. Luckily, not in my case as I found out the other day.

I went to the deli for my morning coffee and left my truck running with the defroster on. When I walked out of the deli I thought I heard a jackhammer going, but there was no construction that morning due rain (the intersection by the deli is being worked on). When I hopped in the truck I realized that the jackhammer was coming from under my hood every time that ac compressor cycled on.

After work I removed the plastic splash shield, started the truck, put the defroster on, and listened to the compressor and the tensioner (adjuster) with my automotive stethoscope, and the tensioner was howling away. I removed the belt and spun it by hand and it sounded like a dry bearing.

Yesterday I went to the local Chevy dealer to get the tensioner from parts, and the manager, (who I know), told me that these things have been selling like hot cakes...he had three in stock. Cost me 34 bucks.

Hopin to find the time Saturday to install it...looks like a piece of cake...2 bolts.

Just thought that anyone who has been experiencing a similar noise might want to know.

Cheers!

OUMike · October 21, 2004

Bud,

About 3 weeks about the tension pulley on my 94' went out on me. Luckily it didn't just snap off, but the bearing broke and the belt slipped. After we replaced the pulley everything seems great and the motor was even a little quieter EXCEPT now when the compressor is on it has that same "jackhammer" sound. I purchased the other pulley a few days ago in hopes that it would fix the problem...do you think that will do it, or does it sound more involved to you than just a pulley swap??

PS - Compressor is brand new...

Autumn · October 21, 2004

Bud,

I wonder if your problem could be the cause of my a/c serpentine belt breaking after only 10K miles? However, my tensioner does not make noise. I will try it today with the defroster on and see if I hear the noise.

BTW, where did you get your bowtie spash guards?

Autumn

budhayes3 · October 21, 2004

Mike-

Hopefully the pulley will fix the problem, that's definitely where my noise is coming from. If not, the noise can by identified with a stethoscope or long prybar used as a stethoscope...but it is kinda scary and potentially dangerous to do, you have to be real careful not to get caught up in the moving accesories and belts.

This will be the second tensioner replaced on this truck. I had the upper, main tensioner replaced under warranty for a similar noise.

Autumn-

If that tensioner is siezing, it will definitely throw the belt...if it's not the tensioner you have a compressor problem (hopefully not). If you remove the belt and spin the tensioner by hand, it should be quiet, if it makes a scraping sound it's no good.

I got my mud flaps from the dealership the same week that I bought the truck in 99, they were in the GM Accessories Catalog. Been on the truck 5 years and still look fairly new.

Good luck folks!

OUMike · October 21, 2004

Bud,

Thanks..

Yea, I didn't think that the 2nd pulley (the one that is fixed?) would cause anything like that. I figured since it didn't move, it didn't really do anything except spin. Upon inspection of the new one, I realized the bearing in the old could just be siezing up. This could be the problem...Thanks for the help.

budhayes3 · October 24, 2004

Just an update...I replaced the ac tensioner Saturday, what a piece of cake. I did it while I did an oil change. Maybe 15 minutes tops. Removed the front splash shield (5 15mm bolts), swung the tesioner down by putting a 3" 3/8 extension on a rachet in the hole, and slid the belt back, towards the engine. Then it's just a matter of removing 2 15mm bolts and viola...it's off. Installation is exact opposite of removal. Best part, no more jackhammer.

Tried something new with the oil change also. Been using Mobil1 5w-30 since day 1, and lately, since I've done my cam and spring swap, I've been real in tune to my engine ticking and tapping...it's always been doing it, but now I really notice it. Of course I rechecked all of the rocker arms and they were good. So I decided to try Mobil1 Truck and SUV formula, it's 5w-40. Maybe I'm crazy, but it seems as though some of the ticking that I get once the engine warms up has quieted up a bit. It's still noisy, just not as bad. Maybe I'm just listening too closely...I dunno.

All in all, it was a productive Saturday.

OUMike · October 24, 2004

Turns out my idler pulley was fine. AutoZone sold me the wrong tension pulley

so I went down to O' Rielly's and got the right one. No more noise. Of couse...now my AC is cutting in and out. Guess its time for a charge...if it isn't one thing its another

budhayes3 · October 24, 2004

Turns out my idler pulley was fine. AutoZone sold me the wrong tension pulley

so I went down to O' Rielly's and got the right one. No more noise. Of couse...now my AC is cutting in and out. Guess its time for a charge...if it isn't one thing its another

<{POST_SNAPBACK}>

Cool man, glad your noise is gone. Too bad about the compressor cycling, like you said, if it isn't one thing, it's another. Hopefully the system is just a little low, probably has a slight leak, unless it wasn't filled completely when the compressor was replaced.

MrBuck69 · October 25, 2004

Bud,

Would you happen to have a part number for the AC tensioner? I'm getting the same noise with my 2000 Tahoe 5.3. I took it to the dealer a couple of months ago for them to check my AC compressor and all they did was change the big belt and the noise stopped. Now the noise is back. I hear it when the truck is idling and it gets louder when I turn the AC on. Aren't there two tensioners on these trucks? One for the big belt and one for the small AC belt?

Buck

budhayes3 · October 25, 2004

MrBuck,

You are correct sir, there are 2 tensioners, one on top and one for the ac. I had the upper one replaced under warranty, and the lower one is the one I did Saturday. According to my recipt from the dealer, the part# is 12580196, list price $45.45, I got it for $34 even. Sorry I don't know the part# for the upper one though.

MrBuck69 · October 25, 2004

Thanks Bud,

When I stop the noise I'll post the details. I appreciate the info.

MrBuck69 · October 27, 2004

I was all set to buy an AC tensioner and belt then I decided to spray a little belt dressing on the big belt and it stopped the noise. I don't understand it. I changed the big belt twice due to this noise. It takes like 2 months for the jack hammer noise to come back after installing a new belt. Any ideas on why this noise comes back?

budhayes3 · October 27, 2004

I was all set to buy an AC tensioner and belt then I decided to spray a little belt dressing on the big belt and it stopped the noise. I don't understand it. I changed the big belt twice due to this noise. It takes like 2 months for the jack hammer noise to come back after installing a new belt. Any ideas on why this noise comes back?

<{POST_SNAPBACK}>

The belt dressing is more of a band aid...it probably changes the friction of the belt on the tensioner and disquises the noise. If you get the opertunity, crawl under there and release the tension and slide the belt back. Spin the tensioner pulley by hand, it should be fairly quiet...if it makes a slight scraping noise, it should be replaced.