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PS AC Belt Keeps Slipping Off

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RJ_IS_BATMAN

Proven Member
105
19
May 7, 2020
Ontario, California
Hey Everyone,

Another issue to add to my many fixes ive been doing on my 420A! I purchased the car without an ac or ps belt, i purchased a duralast belt and within 5 mins of driving it just got tore up and spit out in pieces. I got a warranty replacement and so far this one has slipped off 3 times. I made sure each time to tighten the belt on the tensioner accordingly to the manual but still it keeps slipping off. Not sure what to do at this point, i want to keep the PS and the AC since i live in 100+ degree weather in the summer.

Any thoughts or ideas?
 
Are you sure you have the proper belt cross section dimensions (width and depth for a V belt or ridges (or micro-grooves) width and depth for a serpentine or poly-v belt)?
For example, the depth must not be deep enough to ever touch the bottom of the pulley groove or it will never stay tight and fly off or self destruct. Yet it should match the pulley grooves shape.
 
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https://www.autozone.com/ignition-t...inental-serpentine-belt-4050508/940887_0_8287

I used this one on my 420a and haven't had a problem since and I got PS an AC also check the pulley its self are there knick's or cuts in grooves of metal that will also tear a belt up as well as over tightening and the specifications of belts, the belt you bought is longer and is also for the Idler pulley. the belt I suggest is the Continental Serpentine belt would give a tighter hold. specs are as follows

Continental Serpentine belt

Part # 4050508
WEIGHT 0.28lbs
WARRANTY
Notes
Poly-V A/C & P/S
Belt Material EPDM Rubber
Temperature Range Minimum (°F) -40
Top Width (mm) 0.7
Temperature Range Maximum (°F) 225
Effective Length (in) 50.8
Belt Rib Quantity 5

Duralast Serpentine belt
Part # 510K5
WEIGHT 0.25lbs
WARRANTY
Notes
Poly-V PS, A/C & Idle
Belt Material EPDM Rubber
Temperature Range Minimum (°F) -45
Top Width (mm) 0.68
Temperature Range Maximum (°F) 265
Outside Circumference (in) 51.56
Effective Length (in) 51
 
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Thanks for the information, i was planning on getting that belt when i originally was going to change it but it was out of stock. The pulleys same fine with no knicks or cuts, it just seems to keep slipping off.

I literally will drive for 5 mins and just lose power steering and the ac, I drive back home 5 mins and it always seems to be off at the tensioner, still held on at the power steering pulley.
 
I’ll pick up that belt tomorrow, also when I was working on the tensioner I noticed I had an extra piece not shown in the diagram.

I circled the piece in the attached image. I have one on the pulley tensioner side and also one on the bracket side. Is this normal or did someone added an extra piece in the past?

I just figured it was a space that was needed
 

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Surprised no one has asked if your pulleys are properly installed and free of being bent in any spots or otherwise damaged to where they could throw the belt off. Every time I've had a belt come off, it was due to one of these factors, not having the wrong belt. If your belts are still off, and you are able to reach the pulleys by hand, rotate each one and inspect them thoroughly.
 
Surprised no one has asked if your pulleys are properly installed and free of being bent in any spots or otherwise damaged to where they could throw the belt off. Every time I've had a belt come off, it was due to one of these factors, not having the wrong belt. If your belts are still off, and you are able to reach the pulleys by hand, rotate each one and inspect them thoroughly.

I still have the belt off and am in the process of going through the motor so ill look up the pulleys to see if i can see any damage, from what i could tell they all looked fine and the tensioner is where the belt seemed to always be off
 
Make sure any pulley, usually the water pump pulley, isn't on backwards is what I have found, like Tom was pointing out.
 
Ooooo, IDK. I forgot this was a N/A car so it is probably totally different. Thanks for pointing that out Gary!
 
Even though it's an N/A DSM, it wouldn't hurt to check. I've owned 2 420A DSMs and never noticed.


Let me correct this, I just looked at an engine shot of my last 420a DSM. It appears like it does indeed go on one way, but it could always be flipped.

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So just wanted to give an update, I checked all the pulleys and they all seemed fine with no damage. I took your guys advice and made sure not to overtighten the belt. This time around it seems to be holding, Previously it would come off within 1-2 miles of driving. I have 40 miles so far of test drives and its working fine, Thanks for all your help!
 
And really, when you over tighten that belt, it is hard on the water pump bearing so its good to have it "just tight enough"!
Thanks for checking back in with the update!!! :thumb:
 
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