2001 Cherokee 4.0 small leak

I have a small evap leak on my 2001 Cherokee 4.0, code PO456. I tried smoking it to no avail. However, my Jeep will make a loud “squeal” of sorts that is evap leak related. It goes away randomly but when it is present when I hit the throttle it goes away and when I let off the throttle it comes back.

make sure your evap solenoid is up side right, mine was upside down in my 2000 chased a 0456 code for years before i saw it is stamped on it the direction it is suppose to be, either says top, or bot on it iirc, just take a peek at it to be sure, they made it obvious on it's direction and it is easy for anyone to put it upside down. at least that is what i told myself.

i dont know about the squeal though

A worn seal on the gas cap will do this. So will cracks in the rubber connecting tubes for the fuel vent lines. If you replace the gas cap, use OEM.

The “squeling” noise is very prominent in the engine bay

I am still trying to figure out how the "Jeep will make a loud “squeal” of sorts that is evap leak related". P0456 is common for a gas tank cap like Greenz said. I think you need to check the tension on your belt. One thing I can tell you is that my '00, compared to my '96, is very fussy with belt tension. On the '96 the "yeah that looks about right" method was fine. Not so on the '00. I purchased one of the Krikit II belt tension tools just because of this. When I checked it after using the "yeah that looks about right" method I could not believe how far off I was on the low side. Needed to be tighter. If not that then you need to pull your belt and check all the pulleys.

It’s hard to describe the noise, I’ll try and get a video uploaded to YouTube and provide a link. Sound comes and goes but is coming from the back of the engine bay. When I throttle up “squeal” goes away. I guess it’s more of a whine but hard to describe with words.

I guess the best way to describe the noise is like a teakettle.

does it sound like a vacuum leak? did you check over your evap solenoid yet ?

check all connections to it as well as all other vacuum lines and make sure the evap solenoid is pointing in the right direction.

It sounds like a vacuum leak, it is pointing in right direction. Need to double check connections.

I had code for small evap leak. Traced it to cracking single-wall rubber hose that connects the charcoal canister to the evap pump on the firewall. They use gray plastic tubing for most of it but there are two connectors of single-wall hose. Mine were cracking. Replaced them with double-wall fuel hose. One connectior is aft, the other is in the engine bay near the firewall and subject to heat.

I noticed you are in Wisconsin. Heres the thing, I have an '01 also, and I know EXACTLY what whistling noise you are talking about. I used to live there up until about 2 1/2 years ago. The whistling on mine only came around when the cold weather showed up. In the summer, GONE! I never did figure out what it was, but after I moved here to Arizona, I have never heard it again! Aside from that, I had that code for quite a while, always seemed to come back even after changing the gas cap. Finally found that the little rubber elbow that attaches a vacuum line to the outside surface of the intake manifold was deteriorated. It looked fine at first glance, but as soon as I bent it and inspected it, all the cracks showed up and even a small rotted out hole in it. Changed it out and the code never came back. So just give all those little rubber vacuum fittings a check. Good luck on figuring out the whistle. Or just move to a warm climate to solve that issue!

Also check all hoses that just push on the evp system , I cleaned all those hoses and added a small clamp to them and the small leak is gone , that was about 3 years ago and still no problems .

These fixed the same code on mine:

https://www.amazon.com/dp/B00GHSDJC...colid=K3GZ9V5BTVHB&psc=0&ref_=lv_ov_lig_dp_it