: How much runout is okay?

10-24-06, 10:33 AM
My serpentine belt is chirping. It didn't start chirping until a few days ago. I checked the belt one day, and saw it was one groove off on the crank pulley... So I reseat it and it starts chirping. I thought I had gotten some oil on it or something, so I sprayed the belt with brake cleaner, and it stopped immediately. When it dried it started again.

I sprayed the back of the belt and it did nothing, so now I know the problem is with the grooved side. When I was doing this, I noticed the crank pulley was wobbling a bit. How much... I don't know. Enough to be noticeable. Maybe 1/16"

Now, there is a chip on the outer flange/edge of the pulley... barely 1/2" long. I'm wondering if in the removal process someone dropped the engine on it's pulley - caused the chip - and the excess wobble. (and my chirp and belt jumping)

1. Does anyone have any figures for "acceptable" runout on the crank pulley?

2. How much work is it to replace the pulley? I'm not even sure if a puller would fit down there.

10-24-06, 11:47 AM
The dampner is a casting so it is not unusual to see what looks like a wobble. You might also have broken the bond on the rubber between the hub and the rim. In which case it can come out of there like a grenade. I would do a very careful inspection and replace the whole thing if it looks damaged in any way.

10-24-06, 09:46 PM
Don't worry about the outer surface of the damper "wobbling" a bit. Take the belt off and look carefully at the runout of the belt grooves. That is what is important. The front face of the damper is as cast so it can look like it has some runout but it is really not an issue. The belt grooves should have very little to no runout. If they have discernable runout then I would consider replacing the damper. If the damper has really been hit hard by dropping the engine on it or something like that then it could easily be damaged as dkoz indicates and should be replaced. You need a special damper puller and installer to pull the new damper on. Not impossible to do in the car. Work thru the right front wheel well with the tire/wheel off. Remove the inner fender splash panel and you will be staring at the damper. You will probably have to loosen the cradle on the right side and lower it slightly to get sufficient clearance to remove the damper.

10-24-06, 10:03 PM
The belt grooves should have very little to no runout. If they have discernable runout then I would consider replacing the damper.

Cripes. I was looking at the belt grooves. :(


Well, at least it's only a $30 part. Rock auto says: DORMAN Part # 594195 - $30.79.

I'll do a search on replacing it. Thanks guys

edit - looks straightforward. Bolt is lubed with oil, tightened to 44ft-lb, then an additional 120 degrees. Does autozone rent the puller and installer? Just the "standard" harmonic balancer puller, right?

10-25-06, 03:20 PM
Well, I'm not convinced it's the cause of my chirping (although it's too late - I already ordered it)

After a second look, it doesn't appear to be wobbling at all. It must have been the light/dark patches playing tricks on my eye. Another thing is that the chirping is about every 3/4 of a second. The crank pulley is rotating 10+ times a second. The chirp isn't that fast. This leads me to believe there's a glazed spot on the belt or something.

Although that doesn't explain the belt jumping.... I had to double check that all my pulleys have 6 grooves. Now I'm just confused. Also, it has all new idler/tensioner pulleys and I bought a new tensioner last year. Watching it move, it isn't in time with the chirps, so I know those aren't an issue.

10-25-06, 07:11 PM
Carefully hold a bar of soap on the grooved side of the belt for a few seconds with the engine running. This should quiet it down.

10-26-06, 12:02 AM
If you do replace the damper remember that the tension from the damper bolt is what holds the damper tight to the oil pump drive sleeve....in other words if you screw up tightening the damper bolt you won't have oil pressure or could loose oil pressure....so make sure it is installed and tensioned correctly.

You really do not want to put the new damper on the crank and try to pull it on with the stock damper bolt. It is not long enough to have enough thread engagement when the damper is first starting to press onto the crank and it will deform the first few threads and cause major problems as you continue to tighten it. Use a damper installer to pull the damper into place and make sure that it is completely seated before installing the damper bolt and tensioning it.

It is a good idea to do the torque and angle on the damper bolt then loosen it and redo the torque and angle to make sure it was completely seated.

You will find that it will take about 250 ft lb to reach 120 degrees of angle on the bolt after the initial torque so have the proper tools to reach that sort of torque level as you turn the bolt to 120 degrees.

You will also need to remove the dust cover on the torque converter so as to be able to access the flexplate to lock the crank so that it will not turn as you tension the damper bolt. You will need to make up some sort of lock to engage the teeth on the flex plate and hold it from turning by using one of the adjacent mounting bolts....and/or have someone to help by holding it with a big screwdriver in the teeth of the flexplate.

10-26-06, 03:33 PM
Carefully hold a bar of soap on the grooved side of the belt for a few seconds with the engine running. This should quiet it down.

No need. I splurged the $12 on a new belt, and it's quiet now.


I'll probably keep the balancer just in case...