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Belt Shredding Diagnosis?

V

verrive

NAXJA Forum User
Location
Ellensburg, WA
Hey Guys,
My serpentine started cutting itself up again. When I got a look, the belt was off on both my cooling fan pulley and my I wanna say crank shaft pulley. Is one or the other more likely to be the culprit? Is there a way I can test to see which is screwed up? The belt is off the fan pulley by an 1/4" of an inch and the crank shaft one is off one notch. Not sure if the crank shaft one would be over more like the fan pulley but it has the notches keeping it in place more than the other. Any help would be appreciated :D

I had the same problem before and I got my water pump replaced, problem solved.

- Kevin
 
sounds like the classical harmonic balancer failure. The rubber on the crankshaft pulley fails and the pulley "walks" forward or back.

Get your XJ to the shop tomorrow and do not drive it any more except to get it to the shop. As posted on here over the years the pulley can walk into the radiator OR walk into the timing cover and and eat it up.

Any time over 100K miles they fail, mine failed at 115,000 miles.

Also in the future tell us the year, mileage and engine. I take it you have the 4.0 since that is the engine most who post in here. Eagle found out some stuff on damper redesign and knows what years are affected. I recall he went with the crown automotive damper since it was the stock damper for a late 80s 4.0, do a search or maybel he will post
 
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Whoops, forgot the good info ;) It's a 1992 Cherokee with the 4.0 engine. 145k on the car, roughly 5k or less on the engine. Where is this rubber located? I was looking at this part towards the radiator and it looked a little warped.

- Kevin

PS I hear a little bit of almost a grinding sound. Wouldn't call it grinding as it's not really loud or deep. A girly grinding so to speak.
 
Looking at the crank pulley/harmonic balancer straight on, there is a spoked hub in the center, then a thin strip of rubber, and a weighted piece on the outer rim. The bond on the rubber fails, and the outer piece/pulley can walk in or out as Martin describes.
 
I got out today and snapped some pics. Unfortunetly I'm not seeing what you describe. As well, the pic from the bottom isn't straight on but I couldn't see anything more straight on. You must copy the links and put them in your address bar.

http://pics.bbzzdd.com/users/verrive/Front.jpg

http://pics.bbzzdd.com/users/verrive/Bottom.jpg

Thanks,
Kevin
 
Your harmonic balancer looks fine. The thing that causes belts to jump the track like yours is pulley missalignment. That means one of the pulleys isn't straight. The most common problems are the rear bolt on the alternator coming loose letting the alternator pivot a bit, or the same type thing happening on the power steering pump. Take a good look at your pulleys and make sure they are all straight. Also there is a possibility you got it off by a rib width when you replaced the belt. It is real easy to do. The last thing that causes this is a shot waterpump bearing, but you didn't complain about any noises or leaking.
 
I'll go take a look again when the rain dies down. I don't think it is the waterpump although it did as I said it was replaced. As well I don't think it is the fact it was off a rib, as the belts been on there for a few months. Although I do think it could be the alternator, if I remember right I remember hearing the belt hitting my hood after I hit a bump. Thanks for the idea :D

- Kevin
 
Went back out and felt around the alternator, no luck with that. Here are some pics of the fan pulley that's way off. Unfortunetly it's hard to go off of just pics so I appreciate all the help I can get.

http://pics.bbzzdd.com/users/verrive/FanSide.JPG

http://pics.bbzzdd.com/users/verrive/Fantop.JPG

It looks to me like the Fan pulley is more towards the radiator than the rest.

- Kevin
 
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It's hard to tell from the pictures, but I reread your response and you said there was a screeching sound. From the picture it looks like the fan shaft is not perpendicular to the belt. That would lead me to believe that you have a bad bearing on the water pump. Pull the belt and see if you can wiggle the fan shaft. If it wobbles, that says that the water pump bearing is hosed. Sometimes you can locate a whine/screech by using a small tube. Hold one end up to your ear and use the other as a probe. When you get it close to the source of the sound, you can really tell the difference. Be carefull poking it around those moving parts, it can get quite interesting quite quickly. LOL

The real key is to look real hard at all the pulleys. They won't necessarily be sitting forward or back, but will be tilted. Normally you can spot it by eye.
 
Sorry, I forgot. I still haven't got as much experience with 4.0L's as 2.5L's. They have the fan mounted on the water pump.
 
Ahh, I gotcha. As well, when I was going to take the belt off and look(although I couldn't because it was seemingly impossible to get to the tensioning bolt) I noticed that one of the two bolts on the back of my ps pump are gone. How important are those? :x

- Kevin
 
That is probably your problem. It allows the pump to sit crooked.
 
?

Bah, after looking I sitll can't tell, I give up. I'm gonna give it to my mechanic. After all is said and down I'll still probably end up on top, it will take me like 5 times as long for me to do it than him so oh well :(

Kevin
 
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Re: ?

verrive said:
Bah, after looking I sitll can't tell, I give up. I'm gonna give it to my mechanic. After all is said and down I'll still probably end up on top, it will take me like 5 times as long for me to do it than him so oh well :(

Kevin
Click to expand...

Pull the air box, will give you more room. I have a 98 and it is just a matter of loosening the tension pulley and backing the adjuster off. I'm on my second serp belt at 195,000mi the first replacement went in at 190 or so. At that time I also replaced BOTH my idler pulleys. I also have two TJ's, did both belts in them and both idlers, one was noisy and they are not expensive. My guess is that whoever did the last serp did not tighten the PS bolts back down and they fell out or never bothered to put them back in at some point, just tightening them down enough to work.
How do you check your belt tension ??? finger pressure does not fly, NAPA carries a tension gauge called a Krikit II for about $14, takes the guess work out. Most people guess at 190lbs or pressure is closer to 80....
 
So if I out the air box, I have easy access to the tentioner? As well it's the lower sliding bolt and I couldn't figure out where it goes through. Does anyone happend to know the size and length? I was looking to clean my air filter anyways so this may work well, there was a bunch of bees and months in my air filter :p

- Kevin
 
Well whoever told me about the airbox, thanks :D I took that puppy out, gave it a cleaning and took the old belt off, put the new bolts in and a new belt. When I was checking the pulleys I had a question. Should they move at all? When I was feeling up my water pump pulley it moved some. Not a ton but enough I could notice. It would kinda squeak when I would move it. If I was to fix that, would it be a problem with the pulley or the water pump itself?

Thanks,
Kevin

PS I haven't found if it's fixed or not yet, hopefully tomorrow we will see :D
 
The water pump should not move AT ALL. There should be NO PLAY either radially or axially. If there is, you have a water pump that is failiing. FIx it now, before you are stranded by the side of the road with a cooked engine in your XJ.
 
It is a really good idea to not have ANY movement in any of the pulleys. You might also want to replace the idler pulleys while you have it apart. I do it as standard when I do a belt change. I'm also keeping an eye on my harmonic balancer on my 98XJ, both TJ's are good but I figure when the time comes to put the new rad in in a couple of weeks I'll do the harmonic as a preventative measure, also considering the water pump along the same lines, as long as I have it apart I might as well...
 
Guess I have a chore to do tomorrow then :p Idler pulleys being? I'm really not very mechanically smart. The fact I even did that ups my knowledge some ;) Is it possible to install a new water pump without taking the radiator out? I assume I atleast have to drain the fluid.

- Kevin
 
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