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Author Topic: blowing through alternator belts  (Read 9220 times)

350boatracing

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    • 91 Capri 5 speed Non turbo
blowing through alternator belts
« on: September 18, 2014, 11:11:58 AM »

I drove my 4/91 capri for almost 2 months when the belt broke one day with no warning. I had a garage put one on. As soon as I started the car it squeeled non stop for about 10 minutes until the second belt broke. I drove the car home and got a dayco and put it on. The car ran with no squeeling (only occasionally) for about 2 weeks until it broke again. The first break i don't know what the belt looked like after. After the second break the belt had no signs of wear. On this last break the belt looked like it wore on one side for about the whole length of the belt. My buddy watched me put it on said it looked too wide from the get go. I read about the 2 different alternators that go on these cars. So I called mazda and the guy said it looks like up until 4/91 the alternators were bosch, after 4/91 mitsubishi. He also said it looks like all the belts have the same part number for both alternators. I have a couple questions:
1. What's the oem belt number?
2. If my car was on the diving date of 4/91 which alternator should it have?

Later I will pull mine if needed but I don't want to until I get some other facts.
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blueamber

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Re: blowing through alternator belts
« Reply #1 on: September 18, 2014, 02:28:37 PM »

Early 91's have the Bosch unit (has external cooling fins), later cars have the Mitsubishi (no visible fins), both used the same belt.  Not exactly interchangeable, plug connectors into units are different.
Original alternators in good shape will not give you problems in shredding belts.
It doesn't matter what alternator came with the car, just what is in it now.  Many aftermarket alternators use a different pulley that is not quite right, making keeping a belt on a challenge.

This doesn't sound like the usual belt issue the Capri's have.  Constant squealing then breaking (from overheating) then wearing on one side seems to indicate an alignment issue.  If the water pump was starting to fail, that pulley could be out of alignment with the crank and alternator pulley.  If the alternator mount has worn, that pulley could be misaligned.  If either water pump or alternator is binding internally, that could also wear the belt quickly.

Pull the belt, use a straight edge to verify pulleys are in line.  While the alternator is loose, check for play at the mounting joint, should be 0 play
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350boatracing

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    • 91 Capri 5 speed Non turbo
Re: blowing through alternator belts
« Reply #2 on: September 18, 2014, 04:31:57 PM »

Thanks for the reply. the first break there was no overheating i think they over tightened it. That aside, i had a buddy send pics of alternators off 2 newer capris and the pullies look the same as what I have on my 91. I used a lazer edge and the pullies seem to look inline with it although with the naked eye the alternator pulley looks to side a little sideways. I will pull it and check. I've read tons of posts online with similar issues to this, people with belts lasting 5 months to belts breaking instantly.
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350boatracing

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    • 91 Capri 5 speed Non turbo
Re: blowing through alternator belts
« Reply #3 on: September 18, 2014, 04:33:05 PM »

I also felt to make sure the alt and water pump pullies spin freely.
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350boatracing

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    • 91 Capri 5 speed Non turbo
Re: blowing through alternator belts
« Reply #4 on: September 18, 2014, 05:12:05 PM »

I pulled the alternator with dissapointing news (I was hoping it was just the wrong one). It IS actually a mitsubishi. #90JA-10200-AA and it does have 04/91 Al stamped on it. What in the world could the problem be?
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azgtx

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Re: blowing through alternator belts
« Reply #5 on: September 18, 2014, 07:24:44 PM »

Check to see if the crank pulley has a wobble. B6 motors up until 09/91 had the small nose crank and were prone to keyway failure.
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JJ

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Re: blowing through alternator belts
« Reply #6 on: December 26, 2014, 10:03:12 AM »

I've read about this before but can't remember. how can you tell about crank pulley wobble? if the belt is off will it move by hand? or do you have to see it run?

JJ
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azgtx

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Re: blowing through alternator belts
« Reply #7 on: December 26, 2014, 03:49:03 PM »

Watch the crank pulley while it is running while goosing the throttle. If the car is a late 91( after Sept build ) or newer this is a non issue as the cranks were upgraded.
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mitch1204

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    • 1991 Mercury Capri NA Auto/ 1994 Mercury Capri NA
Re: blowing through alternator belts
« Reply #8 on: December 29, 2014, 03:08:26 PM »

Watch the crank pulley while it is running while goosing the throttle. If the car is a late 91( after Sept build ) or newer this is a non issue as the cranks were upgraded.

Mine was made 09/91. Does that mean I'm screwed?  :D
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JJ

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Re: blowing through alternator belts
« Reply #9 on: January 13, 2015, 10:48:24 PM »

get anywhere on this? alternators can be a touchy subject.  If you put the belt in the pulley, how far down does it go? is it below the top of the pully so it sits down in the v? or does the belt stick way over the top?
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mitch1204

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    • 1991 Mercury Capri NA Auto/ 1994 Mercury Capri NA
Re: blowing through alternator belts
« Reply #10 on: January 14, 2015, 10:13:54 AM »

It should be flush with the top of the pulley. Tension is the key. You don't want it too loose or too tight. I went with about 3/8" deflection both ways on the long stretch. I had some rubber dust at first but that quickly cleared up.

Manufacturer is another. I bought a Dayco off Amazon. It's still holding up well 15 months later.
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JJ

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Re: blowing through alternator belts
« Reply #11 on: January 15, 2015, 11:35:25 PM »

The alt on my car kept breaking belts. When I put my working belt from my working alternator in that pulley, it was a good 1/3" to 1/2" below top of the pulley. I also swapped the top bent arm bracket. it looked like a hare off from mine, so could have put the alternator off center, but i'm not sure what would have solely done it...
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cjizzle252

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    • 91 Capri XR2 89 Suzuki gsx1100 Katana
Re: blowing through alternator belts
« Reply #12 on: January 16, 2015, 09:14:22 PM »

hey guys this belt works perfect for me, and you can order from pep boys with DAYCO part number 15350
http://www.rockauto.com/catalog/moreinfo.php?pk=962496&cc=1196636
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mitch1204

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    • 1991 Mercury Capri NA Auto/ 1994 Mercury Capri NA
Re: blowing through alternator belts
« Reply #13 on: January 17, 2015, 11:55:46 AM »

hey guys this belt works perfect for me, and you can order from pep boys with DAYCO part number 15350
http://www.rockauto.com/catalog/moreinfo.php?pk=962496&cc=196636

Yeah that's the one. All my belts are Dayco.
JJ, I went out and looked at mine. It sits at most 3/16" below the top of the alternator pulley but it only sits 1/16" below the top of the water pump and crank pulley. It could be a difference of belt manufacturers. Alignment is very important. Looking at the manual the Bosch has a two piece pulley and it has a dish shaped washer behind it. The manual makes special note that the washer is put on correctly with the dish top towards the fan blades. Is it a reman? Maybe they screwed up and left the washer out or it's facing the wrong way? Maybe they replaced it with a flat washer? It's a 8mm Allen wrench and 29mm wrench to take the pulley off and inspect. It torques back 40-50 ft lbs.
« Last Edit: January 17, 2015, 12:00:36 PM by mitch1204 »
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JJ

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Re: blowing through alternator belts
« Reply #14 on: January 17, 2015, 08:15:37 PM »

ya, mine is fine now. I'm just noting to people if their belt is too low, it's prob the pulley or pulley placement.
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