steven350

Hello forum,
long time jeep owner, first post.
For the longest I’ve had a squealing issue coming from under the hood, and it only happens during the winter and cold starts. After letting it idle for 5minutes, the noise fades away, and the truck will drive fine with no noise coming back. * note the noise is throttle sensittive*
As the years past I would try to troubleshoot what is it, A pulley? A belt? Vacuum leak? Thermostat ?
I tried to get rid of the sound, but money doesn’t grow on trees, and i can’t afford to keep replacing parts that are not broken or causing the issue.
For the last year the squeal is increasingly getting worse, during hot summer months for the first time, it would come on and stay uncomfortably longer.
If anyone has this issue, or has suggestions that i haven’t tried already, i’m all ears.
2000 XJ 160k

steven350

jordan96xj

The most common cause of that symptom is a belt that is sliding on a pulley instead of turning it. The most common culprits are alternator, power steering pump, and air conditioner compressor. As these are the most likely to be creating more resistance to rotating if they are having problems. However, even if they are all working properly, during the winter when ambient moisture collects on the pulleys, it is not uncommon to have an initial squeal on cold startups because the belt is either too loose or is worn out (the rubber is harder and less grippy). This initial squeal will typically go away relatively quickly as the belt warms up and becomes more grippy, and as any residual moisture is worked off of the pulleys.

1. Check belt tension
2. If that doesn't solve, remove belt and inspect all pulleys attempting to identify if any have particularly hard resistance to rotating (can be hard to tell sometimes)
3. Replace belt if there are any doubts to its age/condition

Ralph77

How did you set the tension on the belt? I used own a '96. The yeah that looks about right way worked fine. My '00 for some reason is much more finicky. So much so that I went and bought this:

https://www.ebay.com/p/Belt-Tester-T...d=192866721746

So if I remember correctly tension for a used belt is bewteeen 140 and 160. New is between 180 and 200. Well I did it by the yeah that looks about right method and can't even begin to tell you how far off I was when I checked with the Krikit II.
I do use the low end of the scale when I set tension.

steven350

Tension was check, new belts have been installed, i don’t currently own n air compressor but i have a bypass pulley installed in its place, and that was also replaced. The crank pulley and water pump were the only parts not replaced , the noise is just so piercing that it’s hard to pinpoint what’s causing it.

steven350

Noise went away after the correct tension was set ?

Dave51

Did you change this thing?

Dave51

The idler pulley. Take it off and see if it's stiff. If so, put a little 3 and 1 oil around the bearing (even tho it's sealed the oil will seep in quickly and loosen it up -- I just did it on this old bad pulley and it works in about a minute).

JGravey

Just a thought, check if it happens with the belt off if you want to pinpoint the noise to the accessories or belt.

Dave51

That noise seems a little high for a ball bearing though. Sounds like the water pump but you just changed that.

Listen to this as you're listening to yours:

steven350

appreciate everyone’s feedback..

im not the mechanically inclined, but if i’m not mistaken, if it was a ball bearing issue, i would constantly hear that noise. correct? i’m only hearing this noise during cold startups only... it fades in 2minutes into idling and it fades out 5minutes after startup.
*side note* if i were to drive my car before the engine temperature hits <150+ degrees the squeal will stay on longer, for the whole duration of me driving. until i get to a stop and it idles. my assumption is that the heat in the engine bay expands some sort of metal and it fades away..

steven350

and since it’s throttle sensitive ( the more gas i give, it goes away) leads me to think it’s a vacuum leak somwhere

JGravey

For this reason is why I am just throwing the idea of turning on the engine with the serpentine belt off. That way you’ll know if it’s something with the engine itself or one of the bearings on the belt drive.

Hope this helps.

steven350

thank you, i will get on this and get back with an update, it’s going to be raining the next few days here. So i’ll get to it when i can.
thank you everyone

Dave51

I don't think you can make an "Always" rule about that.

It don't cost anything to check that idler and about a cent for some 3 and 1 oil.

Test don't guess!