Hissing noise coming from engine disappeares when air con or heater switched on

[Bree89]

Help!!!

My car is now making a loud hiss like noise when the engine is idiling, can not be heard when car is moving but sound disappeares when air conditioner or heater are used. Has been happening ever since Perth had the Freak Storm on monday (end of march) and I had to drive thru massive puddles of water,

Thinking would be a hose problem?

[BerlinaBen]

I had a very similar problem on my VT about 2 years ago. It turned oout to be a small vacuum hose right at the back of the engine, up top around the manifold. Could only just reach it with long nose pliers to put it back on. It fell off a few timesso I eventually used a tiny bit of gasket goo to "stick" it in place. Can't remember exactly where the vacuum tube went or what it was for, but that solved the hissing noise.
Ben.

[strgas]

I had a very similar problem on my VT about 2 years ago. It turned oout to be a small vacuum hose right at the back of the engine, up top around the manifold. Could only just reach it with long nose pliers to put it back on. It fell off a few timesso I eventually used a tiny bit of gasket goo to "stick" it in place. Can't remember exactly where the vacuum tube went or what it was for, but that solved the hissing noise.
Ben.

did this hose run underneath the plenum chamber forward to the throttle body

[BerlinaBen]

hmmmmm, stretching my memory now! Without looking at it again I couldn't really tell you. lol

[BerlinaBen]

can tell you it was a rubber hose, with a hard plastic piece in it which was pushed into a hole in the manifold or wherever it was that it went.

[BerlinaBen]

Yeah, just checked. Thats the one! it comes from under the throttle body, under the plenum to the back left hand corner of the manifold. Can't actually see where it goes from there cos it is covered by an electrical connector. It was very loose on both onds of this tube and could drop off either end without much pressure at all.

[strgas]

its the vacum hose for the carbon canister . it runs to the purge valve on the back of the manifold , common for this hose to come off in LPG engines suffering a back fire as the rubber elbows are only glued on at the factory remove and replace with a single piece of rubber fuel hose is my fix .

[BerlinaBen]

I don't think my car has ever backfired, but like I said, the hose was pretty much falling off when I touched it. the trouble was that it was actually the hard plastic piece on the end of the hose that was loose. The hose itself stayed tight on this so if i had replaced the hose I still would have needed to use the hard plastic "joiner" which was loose. A touch of sealant has kept it in place now though!