belt slipping off

[RacerX10]

1998 4x4 explorer sport, SOHC, 120,000 miles or so

the drive belt (a/c,ps/h2o pump/etc) was tearing on one side so i put a new one on.

the new one did the exact same tearing (about 1/8 on the side coming apart)

looked closer and found the tensioner was tweaked, it was sitting at an angle because the spring inside had broken or something

put new tensioner and new belt on, but it's still tearing up the drive belt about 1/8 on the back side. i look at it after a short run and i see that the belt is coming off of the crankshaft pulley, and riding back towards the block in exactly the same amount the belt is tearing

i know it's a ribbed belt and seems odd that it would do this, but it sure enough is

i've put the same belt back on it that it had original equipment, and the tensioner is one i got from O'Reilly's for about 45 dollars. It looks to be the same thing as the original part, but i'm not sure if the tension amount is the same.

any ideas on this ?

thanks,


dld

 

[RiverRat]

sounds like something is still out of alignment. Check all accessories (p/s, a/c, w/p, etc). Was it in a crash?

 

[RacerX10]

yeah, i'm thinking something out of alignment too, but where do you start looking ?

never been in a crash, i've owned it since it was new.


thanks !


dld

 

[RacerX10]

bounce .. please more ideas .. been several weeks and i still don't have this solved.

thanks !

dld

 

[RiverRat]

Get some saftey goggles or sheild and rev the engine with the belt on. See if you can see which pulley is off alignment. Maybe the bearings of one of the pulleys are broken. I had a honda where the waterpump pulley could be rocked. It had 1/4" play, bearings were shot and the timing belt came off.

 

[yob_yeknom]

With the belt off, try to move the pulleys back and forth by hand. See if any of them have play in them. Make sure all pulley brackets and parts with pulleys are bolted in place tightly.

 

[RacerX10]

checked all the pulleys with the belt off. they all turn smothly and have no play left/right front/back

only thing i've noticed is that the fan seems very hard to turn, it's not free at all like i would expect @ 40 degrees outside air temp and a cold engine.

is it possible that a tight fan might make the water pump pulley hard to turn, and tension too much on the main crank pulley .. making it walk back to the block ?

i think i'm going to pull the fan / fan clutch off, start it up and see what happens.


thanks for your ideas !

dld

 

[my91explorer]

Had almost the same problems and the water pump bearings were bad. It had just enough wobble to ruin and pop off the belt.
Check all the pulleys for any wobble.

 

[RacerX10]

i will check that, thanks 91exp. i keep thinking it has to be somethign with the water pump pulley because that's the last place it goes before the main crank pulley, and that's the one it keeps coming off of.

dld

 

[mrboyle]

Don't rule out the crankshaft pulley! It is possible for the harmonic balancer to fail, allowing the pulley to move back and fourth. This isn't a common problem, but I have seen it happen on several vehicles.

 

[RacerX10]

how can i check for this ? i grabbed it and pulled / pushed but it seemed pretty solid.


thanks !


dld

 

[KEbert]

I would say that it is the bearing in the idler pulley. It may not feel loose, but it is possible that it is causing a vibration strong enough to move the belt.

 

[RacerX10]

idler pulley ? you mean the one on the tensioner ? i put a whole new tensioner assembly on it.

thanks


dld

 

[676cyl]

Check to make sure nothing is loose and rubbing on it.

 

[Fred Garvin]

The idler pulley is different than the tensioner/tensioner pulley.

The idler pulley is up high b/t the alt & the PS pump.

 

[Tiffany1028]

I have a 2001 ford explorer sport(NOT SPORT TRAC). It is a 4.0 SOHC, the 2dr version. It is the first generation also. My husband and I are having the same problem with the belt coming off the harmonic balancer. We have had the tenisor changed, the idler pulley, water pump, and most recently the harmonic balancer. We just put a new belt on this morning, and not even 12 hours later, it is coming off the just the harmonic balancer. But before coming off the harmonic balancer, it squeals like a pig and then once it is on the edge towards the engine block, it is quiet(no squeals). The only pulleys we haven't replaced is the a/c pulley and the p/s pulley. This is our only running vehicle right now. We have lost count how many belts we have gone through. SO PLEASE, WE NEED SOME INSIGHT AS TO WHY THIS KEEPS HAPPENING!