I have some loud squealing coming from the serpentine/accessory belt area. It's sporadic but pretty loud, and persists from idle to 50 mph (probably keeps on going but it's hard to hear at those speeds). I want some help diagnosing this.

I originally though it was the water pump. The pump was leaking every so slightly. I figures the bearings were shot = leaking + squealing. I changed the water pump on the weekend - job went perfect - but the squealing persists.

Is there any good, easy way to check the source other than replacing the accessories one by one? thanks.

 

While the engine is idling, spray the belt with water or hold a tire marker crayon on the belt to apply the wax from the marker to the belt. If the squealing stops, the belt needs to be replaced. If the squealing persists then remove the belt and check the idler and other pulleys.

Jimmy

 

Idler arm and pulley, also go ahead and change the belt while you've got the old one off. Usually the noise happens when under load, sometimes at idle and cruise.

 

Ok... been away on work for a while and finally looking at this.

Today I removed the belt to check it over. I also checked play in the tensioner and idler pulley. The belt looks fine. No cracks, no missing strips etc. The tensioner and idler pulley each have about 0.5mm of play. How much is acceptable? I put the same belt back on and applied a little bit of wax to both sides and, lo and behold, the squealing is gone. I'll give it overnight and drive around a little tomorrow to be sure.

If it's really gone for good, I guess it is the belt...even though it seemed 100% fine. I'm also concerned about the acceptable amount of play in those two pulleys.

 

Pulleys should have no play or lateral movement at all. They should spin completely quiet and smooth as glass when you spin them by hand. They also need to be replaced if they feel rough or gritty when you spin them. The belt can look OK but still be stretched just enough that it squeals.

Depending on the miles on the truck the tensioner may need replacing. With the engine off try to push the tensioner pulley towards the driver's side of the truck. It should not move easily by hand and should not move more than half an inch at the very most. There is also a mark on the tensioner that you can look at for reference with the engine idling. The mark is near the bottom of the tensioner body, hard to find if you don't know where it is or what it looks like. If the mark on the tensioner moves past the reference mark on the bracket while the engine is idling, the tensioner needs to be replaced. There may be Youtube videos on how to find the mark and check the tensioner.

On my own truck I replaced the tensioner at 42,000 miles, and again at about 130,000 miles. Use Napa or Rock Auto if you need a new tensioner. The ones they sell at Autozone are not made the same as OEM and will not work well. At least in my case it didn't. I went through 2 different Autozone tensioners before I realized the AZ part was not the same size or shape. It kept slinging the belt off every time I started my truck. The Napa part was $85.00 but worked great, looked and fit exactly the same as my OEM tensioner. The second one I ordered from Rock Auto, it was exactly the same as Napa/OEM however it only cost about $32.00. I replaced my idler pulley around 70,000 miles. It was squealing but not too bad. A new Napa pulley worked great.

Jimmy

 

Thanks for your advice. The truck has about 83,000 miles and I've only had it for 6 months, so I don't know what has been replaced and what has not.

The tensioner seems quite good. It is not easy to move by hand (or with a wrench for that matter). But the pulleys on the tensioner do have a little give. Almost as if the bolt holding them on needs to be tightened a 1/4 turn. Of course you can't tighten these.... They spin freely and do not have any resistance/gritty feeling/grinding sound.

But maybe the little give on the tensioner pulleys is enough to throw the whole thing out of alignment. I'll check rockauto for prices.

 

both pulleys separate from their mounts. The top one comes straight out and is threaded to the front of the motor, the tensioner is bolted into the arm- whack it with a big wrench in regular lefty form and it'll come loose.

 

When you go to buy the pulleys they will have two listed. One is grooved (Inside of belt is against the pulley) and one is not (OUTSIDE of belt is against the pulley).
Of course if you are replacing both you need one of each.
Not hard to replace at all. MAKE SURE to follow the diagram on the fan shroud for belt routing.
I put mine on and had the engine fan turning the wrong way. I realized it as soon as I started it but it could have been bad