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Serpentine Belt suddenly loose.


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So, i was driving to get groceries, and i think i hear a sound like a spring... and notice i don't have power steering.  I get to the store and pop the hood, and see that the serpentine belt has come loose, and the pulley on the Alternator is spinning freely, like a bolt has come loose.  I manage to get it back home without power steering, or any of the other accessories that run off the belt (kinda scary!)

 

I get looking into it, thinking maybe something slipped to cause the belt to come loose - but the Power Steering pulley hadn't moved a bit - i had to loosen all the bolts around to get it to move at all.  I even fully extended the bolt to adjust the tightness, and cannot get the belt tight.

 

I considered the belt may have stretched at some point, so i ordered a replacement belt, and alternator just to be sure.  that pulley didn't seem right.

 

they arrived today - the belt is exactly the same as the one on there, so that ruled out the belt stretch theory.  I'm stumped.  Something must have moved somewhere to make it so the belt can't tighten up?

 

this is on a 1990 2.5L MJ ...

 

 

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Ok, so that is the typical AC-less set up for the 2.5L. Now you have three bolts for the PS pump loosened right? Two right behind the pulley and the other on the back? Then there should be the two down below the pump. One secures the adjuster in place and the other tighten or loosens the belt. If that bolt that secures the tensioner is still secured the pump won't move with it.

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No, later models might have that but the Renix era does not. The only idler pulley is the one right by the Alt.

I remember going through something like this once, except I wasn't driving I was at home still. But my issue ended up being that nut at the bottom. If the whole pump assembly isn't free moving right now, then something still isn't loose. In order to tension the belt, all the bolts have to be loose and then the tensioner(the long bolt underneath the pump closest to the air box) can be tightened to increase tension on the belt. If still no movement you can always give the pump a love tap with a mallet(rubber).

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Confirmed that all the bolts on the PS are loose, and i have the tensioner bolt fully extended to what should be the tightest point.  The PS Pump is swinging freely now.

 

The thing that is bugging me - when i first started checking everything, the PS Pump was locked down tight, and i've been driving without issue since i bought it a year or so ago... so what changed suddenly..

 

are there any sort of gaskets or liners or something that should be around one of the pulleys that maybe came off? maybe around the Fan Pulley?

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So to follow up... I ended up getting a shorter Belt (70" vs 72") - and it fit great.  From what i can tell the Power Steering adjustment is roughly where it was in the first place.

 

There is still the question of Why - but "Ours is not to question 'Why'"

 

thanks for everyone's input!

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It's been awhile since I had my old 2.5, but from looking at your pics I'm thinking you had the first belt routed wrong.  It should come off the right side of the PS pump pulley like you had it, but then it should go down and wrap clockwise around the HB instead of around the water pump like you show it.  Then it would wrap about 75% around the HB, back up and over the water pump pulley counter-clockwise then over to the alternator.  I see a new alternator there.....did you replace it or have a shop do it?  I'd wager that the belt got re-installed wrong.

 

It's not a hard thing to do to route a belt wrong......every time I take the belt off/on my Focus, I have to concentrate to get it back on the right way.  To the point where I draw a diagram of it before I take it off. :beerchug:

 

edit:  I found a pic.  The red trace is how I think your old belt was routed (I think).....the highlighted trace is how it should be routed.

belt.JPG

Edited by mjeff87
add pic
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You are absolutely correct!  I even looked at the diagram and was certain I had it right... this is such a relief!  I'll be back home tomorrow and will put the right belt on the right way.

 

Thanks to all!!

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