89dieselkong

When my fan engages there is a high pitch screeching/sqealing sound that comes with it. Is this the fan clutch going bad? Is there any other part that it could be? It only comes on when the fan is engaged so I am pretty sure that it is fan related. Thanks!!

Zeus1987

possible serpentine belt slipping ?

papaduck

The back side of the belt (flat side) is probably glazed and the tensioner has gotten weak. I would replace both.

89dieselkong

The tensioner was replaced roughly 10,000 miles ago (not to say it isn't bad) and so was the belt. I'll check them though. Why would it happen when the fan comes on only though? The extra drag created when the fan comes on?How can I tell if the fan clutch is bad?

papaduck

The fan can require up to 20 horse power to turn it and it is driven by the flat side of the belt. If the clutch is engaging when it should I do not think the clutch is bad.

Try spraying some water on the belt when it is squeeling and see if it stops.

89dieselkong

It definitely engages when it should and runs what seems to be fine i.e. it blows hard when needed. It only screeches when it blows hard so I guess it would make sense that the belt might be slipping. I can't put water on it only because it only does it under load, like towing or heavy acceleration from a stop where the fan really has to spin fast.

Grit Dog

Bringing this back up looking for others experience. My truck is doing the exact same thing as kongs. It does not sound at all like a belt squeal, more like high pitched steel on steel, only when the fan clutch is engaged.
I have a belt squeal as well but know the cause of it, got oil on the belt when the hydro boost blew a couple years ago. But it's just a chirping when wet out or AC is on. Tensioner is pretty new and old one was not toast when I changed it.
Anyway it sounds like the clutch slipping when the fan engages.
Of course tough to duplicate since only happens under load. First hot weather and towing this year. Fan normally doesn't engage ever unless hot out and towing.
Thoughts? Tests? Just go get a new fan clutch before this one takes a dump?

Oh and I'd like to find the designer of the serpentine system on these trucks and punch him in the ... Mouth! Lol
I hate taking the belt off and on this truck. Why is the fan shroud not easily remove able? Would solve a lot of problems working on the front of the engine!

Grit Dog

So no one else has had this happen?
Man this place is dead. Why'd everyone leave this site. I like dtr but needs to get on cummins forum I guess.