Thread: Fan belt slippage - cause unknown

Is it definitely the belt squealing and not a leaking exhaust manifold? They sound surprisingly similar?

What about the belt tensioner, have you replaced that? Mine looked fine, but when replaced the squealing went away, must have lost some of its spring...

Is it a new belt? I had a similar problem a while back, turns out a batch of belts made in Italy were made slightly oversize, somehow. A new belt from a different batch fixed the problem, Bob

Thanks, the tensioner and belt are new, and the belt appears to be the right size, and have adequate tension.
Something is "on the way out," and I want to prevent a failure when out the back of beyond (as much as possible!)

You said you get a squeal on startup even if aircon is off.so it`s not likely to be the aircon compressor,the only part rotating is the aircon clutch.
you seem to have checked most things,make sure the clutch is freewheeling.
At the Ks you have,if it hasn`t been done already the harmonic balancer is prob.due for replacement.they can make all sorts of weird noises.Mine rattled,but im told other odd noises can be caused by this.
Not a cheap part,but at those Ks may be a good idea to renew.

Trev.

What brand belts ??. Change to Q&H or Contitech belts (same )..no more squeezing!. They grip on their back side .

I'd remove the belt and start it up briefly.
This will let you know if it is in the belt or as hinted earlier an exhaust chirp.

If your are chasing a belt issue there are a few things to try.
If you have the old belt fit it up and see what it does to confirm Bob's hint.
Recheck the fan bearing, it will only need one slightly notchy spot to chirp.
Mine chirped at idle and was in the adjuster bearing but I see you have done it.

Originally Posted by Wasa57

All seems well until startup (even with air con off) and a shreiking noise eminates, then goes away as speed increases.

By "startup" do you mean acceleration from a standing start? If so you are experiencing the classic "broken exhaust manifold stud causing an exhaust leak" problem, which is common on TD5s. Which would explain why you can't fix it by playing with the belts.

Probably the alternator has a shorted turn on the stator (manufacturing fault) and is loading the belt up when asked to deliver power. I'd follow it up with your alternator supplier.