Had a nasty belt squeal for a while. Kinda embarrassing to drive since it was louder than the engine itself. I could spray water on it and it would quiet down so I figured it's the belt. Bought the one in the picture from Rock Auto and the squeal is gone! Even the signature Cummins chirp on shutdown has gone away. Time will tell how it holds up. Just wanted to share for those fighting a squeal.

Another one that works really well is the NAPA Green strip belt. 

I had same problem, though it was my alternator bearings, new gatorback belt and all good. Although shutdown squick noise came back not long after. 

18 hours ago, Mopar1973Man said:

Another one that works really well is the NAPA Green strip belt. 

I looked at the green belts on Rock Auto. They were the top 2 most expensive, although not much more than what I got.This one is the third from the top. Guess I didn't like green on my white truck 

I went through a few on my old truck before having to replace the tensioner. Tried a couple different brands of belt. Should have replaced tensioner sooner. 

2 hours ago, Dmaney said:

I went through a few on my old truck before having to replace the tensioner. Tried a couple different brands of belt. Should have replaced tensioner sooner. 

Yup, that was next on the list.

I had this issue on my old 12 valve 1st gen 1990 wr 250 4x4 5.9.  Thought it was the belt? wrong. Turned out it was the tensioner pulley bearing.  Was always worse when it was damp or raining outside.

What causes shutdown squeal in these trucks?? I changed the belt to green one and tensioner pulley bearings too. Alternator is new. Still squeals in shutdown.

Squeal is obviously caused by belt slipping on a pulley but what pulley is another question. I've been thinking about that myself, the only thing I can come up with is the way the belt is routed on shot down it may jiggle back and forth enough to cause the squeak. If I had to guess it's probably an alternator pulley, since you can turn it backwards with a ratchet and rotate the engine but if you go clockwise it will just slip. 

The alternator pulley slipping on the belt at shut down is what I was always told back when mine used to do it. Has not done it in a long time.

8 hours ago, Finlandese said:

What causes shutdown squeal in these trucks?? I changed the belt to green one and tensioner pulley bearings too. Alternator is new. Still squeals in shutdown.

 

Basically, the engine can stop rather abruptly but the accessories like the alternator, water pump and fan don't so the usually squeak as the device slips a bit.  

Hi,

I know this is an old topic, but what brand Tensioner do you use?

I put a Gates Tensioner and belt green belt on mine.  It was OK for a few days 

but now it chirps constantly.  Are Gates products off shore junk and I need a Cummins tensioner or what?

 

Thanks.

 

Leaky 

The belt chirping is normal and the cause is the high speed rotating mass of the alternator rotor being forced to an abrupt stop.  As alternator capacity has grown significantly over the years this symptom and worse symptoms for long stroke four cylinder engines and some six cylinder engines (especially diesel engines) have cropped up. 

 

For many long stroke four cylinder engines there was excessive belt movement while the engine was idling.  A one-way clutch (de-coupler) pulley for the alternator was introduced in the late nineties for some four cylinder Chrysler vehicles.  This de-coupler eliminates the tug of war on the serpentine belt at low engine speeds and allows the alternator rotor (not the pulley) to free wheel when the engine is shut off.

 

It was an eye opener for me on my wie's 2006 New Beetle TDI.  I didn't know about the de-coupler pulley back then and I unnecessarily replaced a belt tensioner because of engine noises, intermittent brief losses of power steering, and a serpentine belt that looked like it was wanting to leave the premise while the engine was idling.  It turned out that the alternator de-coupler pulley locked up and was behaving like a solid pulley.   I replaced the de-coupler pulley and the belt ran as smooth as glass, the engine became quiet at idle again, and the brief loss of power steering gone. 

 

I believe starting in late 2006, the Cummins engines use a de-coupler pulley on the alternator.  I know there is one on my son-in-law's '06 and a friend of mine's '07.  There is no belt chirp on these trucks because the alternator rotor can free wheel when engine is shut down.

 

- John

 

Edited March 12, 20196 yr by Tractorman

My trucked chirped for the first several years of owner ship from new. Not unusual.

5 hours ago, Leaky88 said:

Hi,

I know this is an old topic, but what brand Tensioner do you use?

I put a Gates Tensioner and belt green belt on mine.  It was OK for a few days 

but now it chirps constantly.  Are Gates products off shore junk and I need a Cummins tensioner or what?

 

Thanks.

 

Leaky 

Do you mean that it chirps while running all the time or when shutting down?

Edited March 12, 20196 yr by JAG1

It chirps while running.  

I take everything I said, thought you meant at shut down.

5 hours ago, Leaky88 said:

Hi,

I know this is an old topic, but what brand Tensioner do you use?

I put a Gates Tensioner and belt green belt on mine.  It was OK for a few days 

but now it chirps constantly.  Are Gates products off shore junk and I need a Cummins tensioner or what?

 

Thanks.

 

Leaky 

I'm using whatever tensioner that was on the truck when I bought it ten years ago. The belt I mentioned took care of my squeekieness and it has not returned since.

I want to say my truck got the continental brand belt and dont remember on the tensioner. More than likely whatever was at the parts store. Might try to turn them in for warranty and replace. I know its a hassle but sometimes the new stuff isn't right from the get go. May check out alternator bearings as well. 

To fix a squeaky belt, simply put dawn dish soap on the belt inside/outside while its running. You'll be amazed!

If the squeal is traditional for the mighty Cummins so let it be! My truck has never done it.