: AC belt off, Serpentine belt sliding forward????



mlimanti
02-01-13, 01:07 PM
When my A/C went out I look under the hood to find the belt was off and slightly wedged behind the crank pulley. A few months ago the crank pulley separated and shredded both belts, so crank pulley and both belts are fairly new. Same shop now says the water pump is bad because the pulley has a small amount of play in it, which is causing the serpentine belt to walk. There is no leak at all at the water pump, and it just does not seem to make a lot of sense to me. Would the AC belt being slightly wedged behind the crank pulley be affecting the serpentine belt? Is there a separate tensioner for the A/C compressor belt? Weird problem, not really sure where to go from here. Any suggestions?

darkman
02-01-13, 01:48 PM
The operation of the two belts can affect one another. The A/C belt has its own tensioner. If the A/C belt is coming off the more likely cause is the harmonic balancer even if it has been replaced before. If the serpentine belt is coming off it can be caused by a failing water pump since the most common failure is the front bearing although, as you mention, failure of the front bearing is often accompanied by a leak.

dkozloski
02-01-13, 01:58 PM
An engine throwing the serpentine belts off for no obvioius reason can be caused by harmonic vibrations from a badly cracked crankshaft that is ready to let go. This is very common in aircraft engines.

mlimanti
02-01-13, 06:07 PM
The operation of the two belts can affect one another. The A/C belt has its own tensioner. If the A/C belt is coming off the more likely cause is the harmonic balancer even if it has been replaced before. If the serpentine belt is coming off it can be caused by a failing water pump since the most common failure is the front bearing although, as you mention, failure of the front bearing is often accompanied by a leak.

I suppose I should just remove the AC belt and see if the serpentine belt stays in place after that. Then I suppose it would likely be the AC tensioner, is it a separate serviceable part, or is it apart of the compressor assembly, its kind of hard to see??? If the serpentine belt keeps walking I guess I should go ahead with a new water pump.

darkman
02-01-13, 06:28 PM
I suppose I should just remove the AC belt and see if the serpentine belt stays in place after that. Then I suppose it would likely be the AC tensioner, is it a separate serviceable part, or is it apart of the compressor assembly, its kind of hard to see??? If the serpentine belt keeps walking I guess I should go ahead with a new water pump.

The AC belt has its own separate tensioner that is replaceable. The AC belt is much shorter than the main system belt, which is why it acts as an early warning mechanism for a defective harmonic balancer. Many times folks with a defective harmonic balancer report thrown AC belts as the first symptom since the balancer itself is hard to see.

Yes, you could remove the AC belt temporarily to see if the sepentine belt stays on. However, that process requires the removal of the radiator and the serpentine belt to get to the AC belt. By the time you do all that, it might sense to change out the water pump anyway, especially if it has very many miles on it.

Bill Rubeck
02-02-13, 12:25 AM
Only my opinion, (newb), but any real tech should be able to show You proof of worn/bad parts. Ask to see. I have 20+ years in the biz...(sorry, Ford tech, not GM), but I would not want to see a third failure before I got it fixed right. Like I said, only my opinion, but sounds like guessing here.

PISNUOFF
02-02-13, 11:25 AM
Yes, you could remove the AC belt temporarily to see if the sepentine belt stays on. However, that process requires the removal of the radiator and the serpentine belt to get to the AC belt. By the time you do all that, it might sense to change out the water pump anyway, especially if it has very many miles on it.

Are you sure you actually have to remove the radiator to remove the AC belt? I am sure the service manual probably says to remove it but I can't recall if you can get a hand down in there to reach the tensioner.

darkman
02-02-13, 11:38 AM
Are you sure you actually have to remove the radiator to remove the AC belt? I am sure the service manual probably says to remove it but I can't recall if you can get a hand down in there to reach the tensioner.

Nope - I am not absolutely sure. The Service Manual does say that and I sometimes forget that my own front engine clearances are substantially reduced by my Ron Davis radiator. Additionally, if you put the front of the car on jack stands and removed the underneath apron you might also reach some stuff from underneath. The AC belt is inside the serpentine belt, of course, so both belts have to come off.

Twitch
02-04-13, 12:10 PM
You can RR the A/C belt without removing the radiator, I did it.
I forgot exactly how but you need to be under the car. I do remember thinking it would be sooo much easier/faster if I had a helper (probably to hold the tensioner).

Tony

bjazz69
02-05-13, 12:07 PM
Just changed the a/c belt and tensioner pulley yesterday I did not remove the radiator and had a friend help it is a PITA I have smaller hands so o could get down around the hoses from the water pump. Had to place the belt around the crank and tensioner then work it around the compressor while having friend rotate the crank clockwise the belt wants to slip off the tensioner and work behind the crank do it takes a lot of work to get it in place. I used a wire wrapped around a wrench to keep the tensioner pulled down. Also replace the serpentine belt and tensioner pulley.

darkman
02-05-13, 12:26 PM
I think I can change the belts in less time and trouble by puiling the radiator. I have pulled the radiator on mine now enough times that I can it have it out in a few minutes.