2 thing about hissing...

Gris · **Posted:** Tue Jul 10, 2007 1:15 pm

I heard a hissing sound coming from my engine for a while now. I usually hear it when I turn the engine off after driving to or from work.

I had time last night and said what the heck, so I did some investigating. I saw some liquid on various things near the radiator. sniffed it, bingo, antifreeze. I trace it back and find this tiny little crack spewing a the faintest spray. It was tiny. I could barely see the spray, more saw it collecting on a piece of metal nearby than the spray or the crack. But if I wiped the spot on the radiotor dry, it started to get wet again, so I knew that was it. It didn't make sense to me that such a small crack could make such a loud hissing noise. Anyway, I dump some of that alum.oxide powder in and dumped a full gallon of 50/50. It must have been leaking for a while. Ran the engine a bit, added in about 1/4 gallon of 50/50. After a few minutes the leak stopped completely. YAY for that. I turned the engine off, still hissing.

GRRRR

OK, short version...

I have a somewhat loud hissing sound comping from the passenger side of my Jeep. I can't tell if it's from the front of the hood or closer to the firewall. It usually lasts around 20 seconds before fading away. Doesn't matter if I was running the AC or not. Any ideas?

ATXKJ · **Posted:** Tue Jul 10, 2007 1:46 pm

If you're not seeing any drips - I'd look for a vacumn leak
lines going to a power brake booster or any line attached to the intake manifold.

(the old fashion way to leak check was to idle the engine and spray carb cleaner on anything suspect - if it rev'ed up - you found the leak - I'm not sure how well that works on Sensors and computer controls)

Blue KJ in PA · **Posted:** Tue Jul 10, 2007 2:00 pm

I have the same hiss noise now...when sitting still I hear it and it continues 15 to 25 seconds after the engine goes off...I was placing it near the exhaust pipes. I have been blowing it off but it has started to get on my nerves now I'll need to investigate more.

Gris · **Posted:** Tue Jul 10, 2007 2:04 pm

any intake mods? There is that valve thing that connects to the intake tube or stock box. I wonder if that might be leaking.

I caught one of the downpipes on the stock headers some time in the past and put a nice dent in it. I checked it at the time and there was no leak. Maybe it finally worked through. I'll check that out.

Blue KJ in PA · **Posted:** Tue Jul 10, 2007 4:39 pm

My hiss is definitely coming from the rear but it does not seem to be ehaust as the sound does not change as the engine is accelerated. I climbed under after work but I could not find any reason for the sound. Hopefully when it goes in on Thurs for inspection my mechanic will figure it out.

myjeepwalks · **Posted:** Tue Jul 10, 2007 6:55 pm

Mine hisses once i shut it off but it's coming from under the hood. It the the a/c system pressures equalizing. Dont know if this is what you guys are talking about. It does it for about 20 seconds after i shut off the vehicle.

Dutchy · **Posted:** Wed Jul 11, 2007 5:19 am

myjeepwalks wrote:

Mine hisses once i shut it off but it's coming from under the hood. It the the a/c system pressures equalizing. Dont know if this is what you guys are talking about. It does it for about 20 seconds after i shut off the vehicle.

Yes, same here, my 2002 did it and my 2003 does it, after shutting the engine it hisses for 20 secs or so, this is normal.

You can also hear a loud PLOINK from the dash after shutting your KJ's engine for 5 Minutes or so, also normal.

Gris · **Posted:** Wed Jul 11, 2007 9:13 am

yup, that's probably it. Will that happen even if I didn't use the AC though? That's why I was leaning elsewhere.

Blue KJ in PA · **Posted:** Wed Jul 11, 2007 9:24 am

Does the hiss occur all the time the engine is running? Mine does the hiss all the time and it has not hissed from day one...only maybe the last month or so.

Dutchy · **Posted:** Thu Jul 12, 2007 6:46 am

Gris wrote:

yup, that's probably it. Will that happen even if I didn't use the AC though? That's why I was leaning elsewhere.

I'm not sure, but the ac will run on several un-expected ventilator settings, for example the defrost setting will have the ac running as well.

Blue KJ in PA: this does not sound normal as the hissing can't normally be heard when the engine is running (at least not in my case as I have a CRD) and in your case it started doing so suddenly since a month.

Blue KJ in PA · **Posted:** Thu Jul 12, 2007 10:25 am

Yep, my hiss was different. Turns out it was a hose off of the evac (I think that is what he said on the phone) located on the passenger side at the rear of the KJ. I'll add the exact details after I pick it up and see the write up. He also said my rear pads were almost gone but my fronts looked all but new... :shock:

2 thing about hissing...

Who is online