Serpentine Belt Tracking Off Fan Pulley

[TAchterberg]

Last week my serpentine belt split one groove completely off the back side. I replaced the belt, and immediately upon startup it jumps one groove back on the fan pulley, ONLY the fan pulley. After re-positioning and double checking all alignment several times, I still have the issue. Half way up the pulley it's 1 groove off, at the top it's 1 1/2 grooves of, then coming back down the other side it's back to 1 groove off again. A friend mentioned that some guys have shimmed the fan pulley forward with washers in order to stop the "squeek" when shutting the motor off. I removed the pulley but there was no shimming behind it. Does anyone have any idea why the belt would only be tracking off as it rounds the top of the fan pulley but not any others? I tried cross referencing the pulley part number to make sure it was correct, but to no avail. Factory Parts Manual lists the same part number for all 1st Gen's.

 

[RSchwarzli]

Is the pully seated flat? Any run out?



How is the belt tentioner condition?

 

[TAchterberg]

Pulley is seated flat, no run-out. Just replaced the tensioner, no change. Noticed some end play in the water pump, can watch it move in & out with the engine running. Shouldn't have an effect on belt tracking though since it runs on the back side of the belt and cannot "pull" the belt one way or the other, OR ... am I wrong?

 

[TAchterberg]

Removed the fan hub support & inspected all components. No axial or radial runout found on fan hub bearing. Bearing and hub both appear to be seated as they should. Hub retainer and bolt were both in place and tight.

 

[cerberusiam]

Are you sure the fan support bearing is in the right position? I had the same problem and the bearing had moved forward in the support and needed reseating.

 

[HHhuntitall]

Are you sure the fan support bearing is in the right position? I had the same problem and the bearing had moved forward in the support and needed reseating.

Similar experience, only it had moved rearward... ... if the bearing is stiff and not turning freely, it could be generating enough heat and vibration to move in the bore, albeit I don't understand how it could do it... . It's the only explanation I could think of on mine.....



FWIW, the bearing is replaceable by itself... .

 

[cerberusiam]

if the bearing is stiff and not turning freely, it could be generating enough heat and vibration to move in the bore, albeit I don't understand how it could do it... . It's the only explanation I could think of on mine.....

I know why mine went forward. I found that problem at the same time was changing the clutch fan cuz it locked solid. The fan was trying to pull the bearing out and take off. Bent the retaining washer to do it.



The old guy that was helping me cuz I could not get the stupid fan loose (you would NOT believe how long a cheater bar it takes to break that fan loose after running with a seized clutch for a while) #@$%! takes the washer to an anvil and beats it back straight, reseats the bearing and done. Said it happens. That was +150k ago and no more belt problems. :-laf

 

[HHhuntitall]

Ya' know... I had to order a radiator for that truck this morning... . seems where something hit the radiator a while back started leaking... . I wonder if that was done when the fan moved back? The bolt was loose somewhat in mine... . the fan was locked down and I diliberately didn't replace it because my ranch hands don't have a clue how to turn one into the wind to help reduce head pressure for the a/c or to help 'em cool down after pulling a trailer... .

 

[TAchterberg]

Ordered a new bearing today, we'll find out if it makes a difference next week.

 

[TAchterberg]

Replaced the fan support bearing, it didn't have any rough spots or play in it, but had the bearing already so did it as Preventive Maintenance. Grabbed ahold of the water pump one last time before installing the belt, found excessive radial runout this time, along with the end play. Replaced water pump, no more prob's.