How-to change the 4.0 idler pulley and tensioner

MountaineerTom

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This is so simple it really doesn't deserve a How-To, but may help someone new to Jeeps or new to working on vehicles in general.

I started hearing a squeaky/rattle sound near the front of the engine while it was running. I suspected it was the idler pully based on where the sound seemed to be coming from and the fact that the tensioner is less than 2 years old and the water pump is less than 3 months old.

Using an automotive stethoscope, I slowly and carefully fit it between the spinning fan and spinning belt and put it on the head of the bolt. All kinds of crazy noises were coming from it.

Ordered a MOPAR idler assembly from Amazon . It came with the spacer, pully and bolt all completely assembled.

Loosen fan belt,
Remove old pully assembly using a 14mm socket,
Install new assembly and torque to 35 ft/lbs,
Reinstall fan belt.


IMG_9564.JPG
 
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You beat me to it @MountaineerTom - I just did this, the belt, and the tensioner assembly over the weekend along with spark plugs. Your pulley was in better shape than mine was. I had a little guide started but not finished :)

Could not be an easier job. Ended up using Mopar belt and pulley with a Gates tensioner after waffling a couple times. You can use a 1/2'' breaker bar to loosen the belt via the tensioner.
 
You beat me to it @MountaineerTom - I just did this, the belt, and the tensioner assembly over the weekend along with spark plugs. Your pulley was in better shape than mine was. I had a little guide started but not finished :)

Could not be an easier job. Ended up using Mopar belt and pulley with a Gates tensioner after waffling a couple times. You can use a 1/2'' breaker bar to loosen the belt via the tensioner.


Oh dang, I'm sorry. Do it anyway, the more the merrier.

A co-worker told me about this Gearwrench ratcheting serpentine belt tool. I got one almost a year ago and it's great. I've used it on 3 vehicles now and it's very easy to position so that you have plenty of leverage and available movement.
 
Here's the old tensioner and pulley - piggybacking on your post after the part about loosening belt. I've seen the tool you described and it would certainly be helpful for the tight space. I'm not a big guy luckily and I was able to work hands/arms in there with a 1/2" to adjust the tensioner.

IMG_20200202_121028.jpg


If you're replacing everything, you can take the belt off at this point. I removed the pulley with a 14 mm socket like you said. I removed the tensioner with a t40 torx bit. Go easy on that torx, I was nervous about stripping mine and you need to reuse that bolt.

After everything was off, I cleaned the mating surface (where the two nodules(?) fit in) for the tensioner with a wire brush. There wasn't really rust but it was grimy and the video I had watched showed him doing this so whatever.

After that, just put everything back on. I think I used the tiniest dab of antisieze just in case. I just went with "feel" rather than a torque wrench for both the pulley and the tensioner.

For me, there was a sticker indicating how to align the new belt (with and without A/C) - this part was a bit of a pain in the ass working around the fan/shroud but my brother-in-law led me through it.

Side note - I somehow didn't know until recently that you can just push the TJ hood all the way back to rest on the top of the windshield (as opposed to using the hood prop), way easier to work this way.
 
Side note - I somehow didn't know until recently that you can just push the TJ hood all the way back to rest on the top of the windshield (as opposed to using the hood prop), way easier to work this way.

I almost always do that. I've been thinking of adding another set of bumpers on the hood to line up the top of the windshield.
 
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That's a great video Tom, kudos for making it. Simple little jobs like these might not seem worth making a whole video and writeup to some folks who have been doing it for a long time, but stuff like this is what helps get folks into doing some of their own maintenance. It also helps out folks who just want a quick explainer on the simple stuff so they don't have to waste time figuring it out on their own.

I started working on cars in my teens as a profession, and to this day I still google/youtube anything I haven't done before. I watched a YouTube video on how to change the oil on my silverado just so I would know how many skidplate bolts there were and where they were located, where the oil filter was, etc.... Nice work!
 
Thanks.

I should have done a video of the noise but didn’t think of it until I was done.
 
Hi everybody, the T40 holding the tensioner onto my alternator bracket is siezed up. The thing is I have a new alternator bracket to put in and a new tensioner. I don't have the bolt. Were any of you able to find a replacement? Or will I have to figure out a way to reuse that T40?
 
Hi everybody, the T40 holding the tensioner onto my alternator bracket is siezed up. The thing is I have a new alternator bracket to put in and a new tensioner. I don't have the bolt. Were any of you able to find a replacement? Or will I have to figure out a way to reuse that T40?
Saw a video where the T40 was stripped, so they took a grinder/cutting wheel and made the head of the bolt square, then used a 18mm socket on it. Or maybe an open end wench . Might work in a pinch.
 
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Does anyone remember the part number for the belt they used? 4.0 engine?
I bought whatever NAPA pulled up: NAPA p/n UNR 25060882. Kind pricey though, was around 80 CAD which is 65 USD. Haven't installed it yet pending my pulley replacements, but tested the width and groove against the alternator and it looks good so far.
 
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Does anybody know the part number for the bracket the tensioner (and alternator) attach to on a 2002 TJ (believe this is the same for RHD and LHD)?

I am trying to change my tensioner and one of the ‘studs’ had corroded and snapped off in the bracket. I will try to remove the remainder of the stud (any tips appreciated), but I am also preparing for the worst case scenario.