After replacing the harmonic balancer and belt tensioner the serpentine belt falls off?

CJISTOOOLD

MEMBER
1995 PONTIAC BONNEVILLE
2.0L
V6
2WD
AUTOMATIC
190,000 MILES

Replaced the belt tensioner. Then harmonic balancer went. Replaced it. Now the serpentine belt slips off. Checked the bearing and it seems to be good it does not wobble or make noise. Cleaned all the pulleys, feel no play in any of them, and the belt itself is only slightly worn, no cracks or breaks. Could there be a slight misalignment between pulleys from those 2 parts exchanges?

7 Replies

KASEKENNY

MECHANIC
18,907 POSTS

More than likely that is the issue. What I would do is use a laser pointer to see if each of the pulleys are lined up. Clearly if this did not happen until these pulleys were changed, then I would Just lay the pointer in a center groove and point it to the other pulleys and see that it is on the center groove of those.

Here are a couple guides that will help with replacements of these parts in case you see something that you may have missed even though that is unlikely:

https://www.2carpros.com/articles/replace-serpentine-belt

https://www.2carpros.com/articles/how-a-harmonic-balancer-works

Another way is if you have a belt that is slipping off now, you should be able to install it again and then start the engine and watch it to see what pulley it starts to walk off. Normally (not always) it walks off the one that is not aligned.

Please let us know what you find with this, and we can go from there. Thanks

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Tuesday, September 28th, 2021 AT 6:43 PM

CJISTOOOLD

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Thank you for your response, after I posted this question, I went ahead and changed the tensioner assembly again. The belt is definitively walking off the tensioner pulley. I just finished and started the ol girl up. It is still walking off the pulley just not as fast. The belt would start slipping and be off with in 5 minutes. I backed he up, drove her forward and it is just now after 10 minutes of running starting to slip. None of the pulleys are wobbling, there is no play and no noise when I spun them during the exchanging of tensioner assemblies. I am at a loss, I also cleaned all of them when inspecting them with a clean no lint rag. I love this darn car and don't want another!

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Tuesday, September 28th, 2021 AT 8:12 PM

KASEKENNY

MECHANIC
18,907 POSTS

Since the belt is slipping off it may have frayed or stretched the belt that it will do it all the time now.

I would suggest changing the belt again and see if a brand-new belt with the new tensioner still slips off.

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Wednesday, September 29th, 2021 AT 5:25 AM

CJISTOOOLD

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Thank you, I have ordered the belt for pickup. Do you think it wise to change the actual pulley to a metal one with a slight rim?

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Wednesday, September 29th, 2021 AT 6:31 AM

KASEKENNY

MECHANIC
18,907 POSTS

Can you get a picture of the tensioner pulley that you have on there?

If there is not rim on a pulley that has ribs, then I would expect it to walk off.

The smooth idler pulleys are normally the only ones without rims on them to keep the belt from walking.

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Wednesday, September 29th, 2021 AT 6:34 AM

CJISTOOOLD

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This what it looked like when I shut it off last night. I will have to drive it today; I have no choice it is my only transportation and I already missed 3 days in this period for these problems. These are the best I can do right now. When and if it slips all the way off I will snap another, but am only going to slip the belt back on so I can go to Orielys and Petro station. Thanks CJ

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Wednesday, September 29th, 2021 AT 7:58 AM

KASEKENNY

MECHANIC
18,907 POSTS

Okay. That is great. Couple things to start with. First check the parts and make sure they are correct. Both the belt and tensioner just to be sure that is not causing the issue.

Next, we need to make sure the belt is not too loose or tight. Basically, both of these will cause the belt to walk.

I noticed you named the word "Petrol" so is this vehicle not in the USA? I see you mentioned it was a 2.0L, is that accurate?

Lastly double check the routing. I attached it below. If you look at this guide, you will see that most tensioners have a rim on them so if you have one as an option that does, I would go with that if all else checks out.

https://www.2carpros.com/articles/how-a-serpentine-belt-tensioner-works

Thanks

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