So I replaced my belt about 2 months ago and it developed a chirp about a week ago. I checked the tention and its has about 3/4" deflection. It doest do it all the time and is fine at idle. I think the new belt might have just stretched. I don't think its a bearing and sounds like its comming from the alt/fan/ ac compressor side of the motor. I put in a bypass pulley a few months ago and the alt is fairly new. I'm worried about damaging something if I over tighten the belt. Any input?

What brand of belt is it?

You can try isolating the noise, by removing the belt, spin each pulley by hand and check for play, drag, noise. Put belt back on and tighten up. And it needs to decent tight. New belt will stretch somewhat.

Everything is newish replaced in the last 2 years. Idler,alt,water pump, bypass. I installed the bypass because my compressor was chirping a lot.... but it was a different sounding chirp. I checked the alt, idler , and the fan at that time 2 monts ago they seemed fine. Its a Gates belt by the way.

Don't you go dying on me! ;-) to your sig.
no oil or coolant on your belt? Try tightening some more, the belt needs to be really really tight in the XJ...

Dear Bulletstang,

I had a similar problem on my 2000. Get one of those stethoscope tools and start the motor. Touch it to the alternator, the water pump and the AC compressor. My money is on the compressor. I had the same problem last year.

If you buy a compressor make sure you buy the little bottle of oil for it. My new compressor came prefilled. I would not buy used because you just end up replacing it sooner. 4 bolts on top. The belt tensioner is a bad design, but you already know because you did the alternator already.

Problem solved, hopefully.

this

No, I found that that the tighter you go, the more it chirps.

I earlier asked the OP what brand of belt. He said Gates. I chased a chirp with new Gates belt after new one for 4 years. Gates is supposed to be a good brand.

I replaced the last of 5 with another brand. No. More. Chirp.

Embarassingly, I don't remember now what I put on it. Not a Dayco, probably a Goodyear.

I'll check when I get home and see, and let ya'll know.

This is not the only vehicle I've had chirping problems with Gates belts. I'll never buy another one.

Interesting, because does that actually make sence?
More chirp when tightening a belt, would more indicate a pulley as the cause, you'd reckon.
Since chirp is friction-induced vibration, if the belt would be the cause of the chirp, slipage would be suspected...

More on this, actually written by Gates as I now find out, here.

I have to agree with this.
Plus a most of times a new belt has to be readjusted after it breaks and and stretches.

Nope, guys, at least in my situations, it has definitely been the Gates belt causing it.

All the pulleys, idlers, balancers, components, etc. had been replaced over time with little to no effect.

I think the Gates rubber is just too hard a compound. That causes it to slip on the pulley instead of grabbing and conforming as it goes around everything.

FIVE YEARS of that squeak, guys. More of a shriek. Two vehicles. Made them sound like a POS.

Here's the lesson: Get Goodyear Gatorback for serpentine, and a regular Goodyear for V-belts. They don't make Gatorback in V-belts.

Reap the rewards from my trials and tribulations.

Edit: I just read your Gates article. It shows they KNOW their belts chirp. That's why they developed new belts with a new elastomeric compound to eliminate the chirp.

Thanks for the input. I already pulled out my compressor a few months back and put in a bypass. It seems to be fine when the humididty is low or it isnt raining and I live in Seatle so its always raining.

Move down to California. They have a drought going on.

Tightened the belt it was a bit looser than I thought. Now the chirp is steady but I can feel on the back of the belt where its supposed to be smooth it feels different like it might be slightly damaged. I think that is why the chirp is steady. Im just going to order a Goodyear gator back.

This may sound strange but search distributor chirp on youtube.
I thought I had a bad belt on my XJ back in Nov when I put a new belt on.
Finally sometime in mid Dec I stumbled across the distributor chirp issue. The youtube vid sounds just like the problem I had.
Replaced the cap and rotor (super easy) and I made sure to spray some CLP on the distributor shaft before I put the rotor on. CLP is a firearms cleaner, stands for Cleaner, Lubricant, Protectant. Let it seep down the shaft to the bearings.
Not a noise or problem since.
It sounded exactly like a loose belt chirp BTW. It drove my shop nuts because even they couldn't figure it out.