Harmonic Balancer Question

1996 XJ, 2WD, Auto Trans, 4.0, 203,000 miles.

I have been trying to track down a knocking noise that sounds like it's coming from the front of the engine. I don't hear it when it's cold but after a minute or two I can . At idle it's kind of intermittent, but when I accelerate, the noise does too. Can't really hear it at cruise speed. I guess it could be a bearing but I'm trying to diagnose the simpler (cheaper) things first. This is different from the normal noise I've heard at startup for the 4 years I've had the Jeep. I always assumed that was piston slap.

I noticed that the harmonic balancer is wobbling at idle. That's bad, right? It seems like I read on a thread here that it could possibly cause a knocking noise. I was wondering if anyone has cured a noise by replacing a balancer.

I guess I need to take the belt off and run it to make sure it's not the water pump, but I'm not having temp issues right now. I would probably be taking this to a shop for repairs because of time/skill/tool issues.

Thanks for your help.

If your balancer is wobbling it's likely that the rubber between the two halves of the balancer is degenerating. When that happens the belt goes out of whack, the outer part of the balancer moves in OR out and either rubs on the timing cover or pulls the belt off other pulleys.

In the process it might make any sort of noise. If your balancer looks anything like this one, it's on it's way south.

Ok, thanks. I need to take a closer look at that tomorrow. I'm sure it needs replacement since it is wobbling. Just hoping that might cure the noise as well.

tnjeff said:

I'm sure it needs replacement since it is wobbling.

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correct-- if it's wobbling, it's done. Fix it first, and see where you are after that-- you'll probably solve half of your known problems, and a bunch you didn't even know you had.

Thanks. It'll probably be a week or two before I can get it done but I'll post the results here as far as the noise.

First clue I had mine was going south was a piece of rubber slapping the cooling fan, 87 Renix XJ.

Be sure and check the timing chain cover bolts tight. Maybe even consider replacing the front crank seal and the timing chain cover gasket while you're in there.

Both my '84 and one of my '01 XJ have had loose bolts after many years.
The '01 had one backed out and rubbing on the balancer pulley's back face.

Well, I had it replaced at a shop (165.00). Didn't cure the knocking noise but I guess it needed to be done anyway. I will check the timing cover bolts if I can get to them. I guess it's probably something internal though. Doesn't knock until it's warmed up. It's a shame, because it's running really well.
I guess I'll keep on driving it because I really don't have any money to put into it right now, and I need it for transportation but I probably ought to start looking around for an engine.
I'm through buying cars. I love my jeep and I'll be driving it for as long as I can.

tnjeff said:

Well, I had it replaced at a shop (165.00). Didn't cure the knocking noise but I guess it needed to be done anyway. I will check the timing cover bolts if I can get to them. I guess it's probably something internal though. Doesn't knock until it's warmed up. It's a shame, because it's running really well.
I guess I'll keep on driving it because I really don't have any money to put into it right now, and I need it for transportation but I probably ought to start looking around for an engine.
I'm through buying cars. I love my jeep and I'll be driving it for as long as I can.

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What brand of oil filter are you using?

There are common sources of knocking sounds from the front of the engine. The water pump is the most common, followed by AC pulley/clutch, Alternator, PS pump, and even fan clutch.

I've used wix filters and Castrol 10w30 high mileage since I've owned it, changed every 3000 miles. I'm getting the rubber hose out today and see if I can't narrow down the location of the noise a little closer. Don't think it's the ac, and I replaced the fan clutch last summer.