serpentine belts not lasting long

rwms666sc

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Jan 8, 2019
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HI, I am new to posting to the Buick Forums here, though I have read many over the years and am grateful for much good advice. I have an 87 GN that I have had for almost 30 years, with high miles. Recently, I have had trouble with the serpentine belts crapping out. I have put three new ones on in the last month (not cheap ones either) and within about 5 minutes of idling, they somehow start coming apart on the engine side of the belt. I have checked all the pulleys etc. and don't see any way they should be getting cut. The only thing out of the ordinary I noticed was the tensioner sort of 'pulsating' when the engine idles low. Has anyone else had this type of problem? This is the first time I've encountered it.
 

Chuck Leeper

8/10's of a century!
Staff member
May 28, 2001
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Check the idler position. There are gauge marks on it.
If it's loose/spring tension low, it could cause the issue.
If the belt is too long, same thing.
 

earlbrown

runs with scissors
May 26, 2001
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Here's a side by side shot. On the left is acceptable with a tentioner in great shape, on the right is the desired result no matter what shape the tentioner is in.

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Notice the intercooler bracket and A/C nut for reference. The snug belt is close to the round bar, and the 'correct' belt has the pulley slightly overlapping the A/C nut.
 

scgnx2

Member
Jan 24, 2009
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A loose AC compressor did the same thing to my belts. Under load the Compressor would swing out of alignment causing the belt to run on the crank pulleys lip. Lost the hood liner as the belts tore that up too.
 

DR BOOST

Technical advisor
Aug 2, 2001
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The stock size GM Parts belt for a 1986-7 turbo engine is 1618 mm.

I have seen aftermarket GN belts sold by auto stores can be too large, measuring up to 1642 mm.
There is also another situation that makes this problem worse. A non-stock alternator such as the commonly used LT1 alternator uses a smaller pulley which requires a shorter belt.
 

rwms666sc

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Jan 8, 2019
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Okay, here is a little bit more info....I did replace the alternator about two years ago, but turned in the old one to NAPA. NAPA man said it was a match for the stock one, so I trusted him. Also, as far as a pic of the tensioner, I have already taken the old shredded belt off, and have to get a new one before I can send a pic. Will try to get a Gates K6063 as mentioned. Thanks.
 

DR BOOST

Technical advisor
Aug 2, 2001
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Also check the crank bolt. It is the big 1 1/8" in the center of the crank pulley. a walking balancer will do this.
 

TurboBuRick

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Staff member
Feb 18, 2006
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Look at all the pullys. Look at the edge on the side the belt is being chewed up on. Look for one with a shinny metal edge. That could be a tell tale sign of the one causing an issue.

Also snap some pics
 

rwms666sc

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Jan 8, 2019
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Put a new tensioner assembly on, another Dayco belt (kept my new Gates belt for later), cranked up and all seemed fine. Drove about 12 miles to gas station, everything still fine. About 5 miles from the house on the way back, I heard the new belt start to separate again. Made it to the house okay: I noticed that about 1/5 of the belt inside was cut and gone. This time I saw that all the accessory pulleys had the cut down belt aligned with the outside of the pulleys whereas the engine pulley (crank pulley) was aligned to the inside. I guess this must be the culprit, even though I have not done anything to it over the years as far as removing it, etc....
 

TexasT

Texas, Where are you from
Sep 10, 2002
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another thing that lets things get out of alignment is the "ell" bracket not being reinstalled in the Dr side begin the alt/ac compressor. Ac compressor can become worn and the pulley wobble all over the place. But it sounds like you found your problem.
 
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