vacuum leak( hiss sound)

[nikstik]

Hay Guys I keep hearing a off and on hissing sound coming from just behind the drivers side rear rocker cover. Its driving me mad as I can't seem to track down whats leaking.
Its very quite and intermittent and no fluid is present. Its leaking air I'm sure but what??

Niko.

[darcycammo]

how high is your rpm because maybe a hose has come off or has a crack in it somewhere ?

[noddycommodore]

Your brake booster may have fractured or is starting to rust out. If you un plug your booster and block the vaccine line going into it see if the hissing noise goes way

[nikstik]

Brake booster is good, it seems to be coming from right next to the rear of the rocker cover and its not a very loud hiss. Will try and check more today.

[nikstik]

how high is your rpm because maybe a hose has come off or has a crack in it somewhere ?

I think rpm is ok too, will check.

[1_johnboy]

vacuum leak to the heater tap?

[nikstik]

Don't think so as its coming from that back corner more near the engine. Had another look see just now and it almost sounds like its coming from the trani filler tube but not. Prob is its not a constant sound so I can't locate it quick enough.

[VYMAD]

It can't be the actual rocker cover leaking or oil would be present and it wouldn't be making a hissing noise. It has to be one of the vaccum lines going into the plenum area. Have a very thorough check over all these hoses. A small split can be hard to see, so you'll need to just take your time.

[nikstik]

Cheers, Checked for codes and got zip too. Will keep looking.

[the_doctar]

The hose from the throttle body that runs through the valley

[aceventura]

Vacuum hose to the fuel regulator?

[nikstik]

Could be, I'll do a soapy water test and see if I can see the leak. (bubbles)

[Cobra Clutch]

Don't think so as its coming from that back corner more near the engine. Had another look see just now and it almost sounds like its coming from the trani filler tube but not.

I was topping up the tran fluid today and I have the exact same thing.

My A/C gas has gone recently, so I assumed I already had a leak somewhere anyway.

[nikstik]

Cobra, you may be on to some thing here as ac doesn't work too. No cold air coming out the vents.

[Sp3cial K]

hey guys, i have a 97 VS ute and have the same problem ( i think ) i have a sort of whistling/hissing noise coming from around the back of my engine near the rocker covers. Did anyone find a solution to the problem?

[BNGRANT_99]

I had the same thing, took me a few days to track it.. found that the emission control line that attaches under the throttle body was loose. I guess they were glued in originally. Pulled it off with alot of force and re-attached with hose clamp. and no more noise.