hot day and hissing

Smudge · 15-02-2006, 01:18 PM

I was driving my AU1 XR8 yesterday...it was rather warm (35degrees) and humid and when I parked I walked past the passenger side and noticed a hissing sound.

Popped the bonnet and noticed a lot of condensation on some pipes where the hissing was coming from, and I also noticed bubbling in the overflow reservoir (I think thats what it is) but that just looked like coolant flowing back into it...

Since I assumed the hissing was due to condensation build-up from the air-con, I took her for a run w/out the air-con on and got no noise on parking.

I have read on here that the XR's run hot and need to be "driven accordingly" (woteva that means), but I thought it wise to ask people here if they think that sounds normal enough to happen?

Thanks,

Smudge

XR6-VCT-2000 · 15-02-2006, 01:37 PM

I dont know about on XR's if its normal , but it sounds normal to me as i used to have the exact same thing happen with my old XE with the v8 and aircon. It was explained to me that because of the very high temperature water from the engine / mixing with the cold/cooler water coming back out the aircon unit (and it's colder than usual because of pipes condensation which occurs on hot days )... the two different temp waters mixing together again build up exreme pressure/bubbling, and that presssure is released from the radiator overflow - because of the high pressure u'll get that hissing or squeeling noise .
Anyway, i was told on days like that to turn off the aircon a few minutes before stoping the car , to allow the condensation on the pipes to unfreeze a bit and bring the aircon unit back to a normal warmer temp., worked form me and never had any problems with it after that .. and that was ONLY on real hot days i had to do it. And it was only on the real hot days i got condensation.. But hey - thats a sign ur gas is good in it ! ..lol

XR6-VCT-2000 · 15-02-2006, 01:44 PM

Oh..sorry - also ... if u have any exposed aircon piping under the hood , covering it with that black 'soft pipe foam' with greatlly readuce any condensation on your aircon piping/tubes on really hot days (u can get it from 'clark rubber' cheap ), thus helping keep the aircon unit under the hood at its normal temp, instead of the pipes making it to cold - and making the water coming out of it to cold too. ....

XR6-VCT-2000 · 15-02-2006, 01:52 PM

but ......'but !' ..don't quoet me on this with the xr's ! , i was going off the setup of my old 351 cleveland and the aircon unit on that had the water running the the back of the unit too. I haven't even remotelly looked at the aircon setup yet on the xr's !! - darn i dont even know if they use water ??? ...lol

fairmont1998 · 15-02-2006, 05:08 PM

Unless you saw steam coming out your coolant bottle the hissing would have been the gas in the aircond system. Once you turn the motor off the gas continues to circulate in the system until the pressures in the high and low side are balanced.

Condensation on the large pipe running from the firewall to the aircond compressor is perfectly normal and acceptable.

The coolant movement in the bottle is also normal, even thought the motor is off, the coolant still moves around the system due to the fact that heat is still transferring out of the motor into the coolant. You will know if your motor is too hot when you stop it, you will hear distinct bubbling coming from inside the motor, and probably hissing from the coolant bottle. That is coolant boiling.

**Mechan1k** · 16-02-2006, 08:07 AM

It's your aircon system makeing that hissing sound ... my Territory does it as well and so does the AU ute. All the exposed piping has condensation on it ... and is bloody cold to the touch as well.

On really humid days ... my console around my air vents gets condensation and you can see the cold air vapour pour out of the vents in the sun ... pretty trippy actually.

xd5.8l · 16-02-2006, 06:15 PM

The hissing noise is just the accumulator releasing the a/c gas from the high pressure side of the system (big black tank on left side of firewall. It is like a TX valve/reciever drier in one.

stiddy · 16-02-2006, 08:17 PM

Quote:

Originally Posted by Mechan1k

You can see the cold air vapour pour out of the vents in the sun ... pretty trippy actually.

lol and I thought I was seeing things, makes me feel a little better knowing its not just my car with mist coming in from the vents..

but yeah xd5.8 pretty much summed it up.. its nothing to be worried about.. just the high pressure end of the a/c venting some built up pressure..

Smudge · 17-02-2006, 10:04 AM

I actually wasn't that worried just thought i would ask "in case", so I figure I must be learning something about cars after over 12 years of driving hey?

Thanks for the replies to guys most helpful once again.

sanjay · 08-03-2008, 06:49 PM

sorry to bump an old thread but its good to know this is the source of my hissing (AU XR6) as well! recently had the aircon regassed and had never heard it before, really hot in adelaide today (39 degrees). good to know its nothing serious (sick of spending money on this car! another $300 for 2 front tyres, alignment and balance today! :()