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New noise - 300Tdi

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300tdi tdi
2K views 9 replies 8 participants last post by  roverman2010 
#1 ·
Two days before fixing the starter on my 90, my 110 started with a new noise.

300Tdi.

It seems to begin after fully warm. Most often at highway speed. Sounds like the squeaking/squealing of a lose alternator belt. But I don't think a serpentine belt can slip or squeal like that.

Or can it? The idler pulley seems to keep the correct tension.

My next thought was the accessories. I've checked idler pulley, water pump, alternator, nothing obvious. Except the idler has a little play.

I have an electric fan, so no viscus fan.

Ideas? What else to check for? How do I verify the idler is good or bad?

I'm avoiding driving it for now. Good thing I have my 90 running again.:grin

Thanks as always.

Mike & Carrie
 
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#3 ·
I'm thinking it's the bearing in the serp idler that is mounted on thr case. It's a common failure point.

Good news is that the bearing is super easy to replace with a press or a big socket and a hammer, iirc bearing numerous is a 6203-2rs (dual rubber seal)
 
#5 ·
My adjuster pulley bearing started doing that a while back. Have you tried the old trick of putting a metal rod/screwdriver near the pulley and putting the other on your ear to determine the source of the noise? Also try spraying the belt with belt dressing - if the noise goes away, then your belt is squeaking.
 
#8 · (Edited)
Can anyone say with certainty, is the tensioner pulley bolt left or right hand thread?
With much certainty, I will say that a tensioner pulley bolt is definitely left or right hand thread. Just not which one. ;)

A belt/tensioner pulley bolt will be threaded to tighten in the direction of belt travel, so that if its bearing or bushing binds/drags, it won't loosen and cause confusion and delay.

A viscous fan bolt is threaded to tighten with (or be tightened by?) the drag of the viscous coupling and fan, since those have drag by design. On some vehicles, one just installs them snug with fingers and they self-tighten further when the engine is started.
 
#9 · (Edited)
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