Screeching/chirping (crickets?) at 1200 RPM

[heydanno]

Hi folks,

Noticed recently on my 2000 UZJ100 with 190k a screeching/chirping/crickets/cicada like sound coming from the truck when driving around town. It happens around 1200-1500 RPM; if I goose throttle a bit or let off to get away from that range it goes away. My foot doesn't have to be on the accelerator to get it happen, I can be coasting with the RPMs dropping through the range and it will rattle. It's pretty loud, especially when there is a wall to reflect it, but so far my attempts at recording it have failed. Could it be a loose... something that resonates at that RPM? Any thoughts?

Thanks.

 

[adrenalinefjz80]

Check your serpentine belt tensioner. Might have locked up or bearing is making rotational noise. Also might be cat shields rattling under car, so you need to locate where sound is coming from.

 

[marshotel]

When my '98 LC did this, it was the heat shields on the catalytic converters rattling. It would rattle around 1200-1500 rpm, but not at idle, nor at higher engine speeds.
https://forum.ih8mud.com/threads/vibration-noise-in-99.27565/

The problem can be fixed with hose clamps and high temperature caulk:
https://forum.ih8mud.com/threads/heat-shield-fix-where-in-tysons-va.205408/#post-3043993

Or you could replace the heat shields with new.

I would check the heat shields on the catalytic converters first by tapping on them to see if you can replicate the sound.
hope this helps

 

[dougc]

I'm no expert by any means, but I had a chirp like that a couple months ago and it ended up being my driver side front wheel bearings. I ended up replacing both sides. give the wheels a lateral shake just to make sure. It drove me nuts driving next to any type of jersey wall or even other cars.

^ these previous suggestions are also good ones. Hope this helps.

Doug

 

[NWForester]

@heydanno, I have the same thing going on with my 2000 and I have not figured it out yet (though I haven't dedicated any time to troubleshooting either).

I have clamped my convertor shields previously, and to be honest the sound is different this time; the convertor shields are a rattle.

I would like it to be the idler pulley because that is a known issue, but I suspect it's something different due to the fact that the sound doesn't change with engine or vehicle speed.

Please post back here if you get it sorted.

 

[heydanno]

Thanks for the suggestions, everyone. I tapped around the cats and I don't think the shields are loose. I didn't have much time this evening but I was able to get the noise to occur intermittently when revving the engine in the driveway (so I don't think it's wheel bearings), and it does seem to be coming from the engine compartment. I will look more closely at the idler and tensioner pulleys for the drive belt to see if one of them is the culprit. I have records from the PO and the idler pulley and drive belt were last replaced at 75k miles. The tensioner may still be original.

 

[spressomon]

Recently had similar chirp. I had the serp belt idler wheel sitting in my parts pile, thank you @beno, and finally swapped it out (5-minute job). No more chirp. I've also had similar chirp come from dry alternator bearings...too many water crossings.

You're on the right path...

 

[ton504]

I had a chirp too. I replaced my fan bracket yesterday.

Take off the belt and start spinning some pulleys. They will usually show themselves.

 

[lrowe_csp]

I had a chirp, replaced the tensioner and serpentine belt and the chirp is gone...

 

[heydanno]

Thanks everyone. As suspected, it was the serp tensioner. I installed the new one (following these directions) and the chirp is gone.

However, I managed to cause a small, temporary antifreeze leak in the process and about a teaspoon of antifreeze dripped on the timing belt during the time the tensioner was removed (RTH thread here). Everything I read says anything but air touching the timing belt is death... am I in for a TB replacement now (current one is less than a year old)? One step forward, one step back!