'79 911 Turbo Waste Gate

Germaneighter · 11-11-2002, 07:26 AM

When the waste gate operates, does it make any noise?

arrivederci · 11-11-2002, 10:39 AM

No, the stock wastegate won't actually make any noise. You may hear a hissing noise if yours vents to the atmosphere (through a separate muffler). Some 930 wastegates vent back into the muffler.

I have GHL headers and muffler on my car. The kit came with a straight pipe off the wastegate. When the wastegate cracks open, you hear an unmuffled flat 6 (the left 3 the cylinders, I suppose) barking at the ground. Good stuff...

Germaneighter · 11-11-2002, 10:56 AM

hmmmm,.......I am looking at taking ownership of a buddy's '79 turbo. All seems well except a noise when the turbo starts to kick in. It sounds like an exhaust pipe knocking against something solid.....a low frequency bumping sound. Thought it might be the waste gate. I am new to turbos......
Some have said a pulled head stud. I haven't had a chance to pull valve covers yet, to confirm.

To me it sounds more mechanical than pneumatic.

any thoughts?

arrivederci · 11-11-2002, 11:31 AM

Does the pitch or frequency of the noise change as the revs climb or as speed increases...is it dependent on a specific gear? It might not be exhaust/turbo related at all...

Have you ruled out tranny/diff problems? What about something in the CVs or bad wheel bearings? Torque can do all kinds of things. The turbos also tend to squat quite a bit under boost in 1st and 2nd gears...changing the suspension geometries. The wastegate is a pretty simple device. IMO, not much can go wrong with it...just a big spring and a valve.

Germaneighter · 11-11-2002, 11:55 AM

the frequency or pitch is unchanging at different RPMs. Appears to deminish at higher RPMs but can't be sure. I ran out of road....

The noise is also sparatic like an ignition misfire.

Thinking about it, it sounds almost like a backfire that is muffled.

beepbeep · 11-11-2002, 03:08 PM

Take warmed up car to long strech of highway, do some full-throttle runs in 3:rd gear, take some tape-recorder with you, recor the sound and post it here (or e-mail it to me).

Wastegates can make lot's of noise if they vent to atmosphere, but it surely isn't low-frequency. If sound isn't RPM-related then it's probably some (big) rubber-seal that is leaking, opening and closing.

Check big "L" shaped rubber hose between CIS and turbo for cracks and check intercooler seals.

It sounds almost like your intercooler isn't properly sealed and pops up and down under boost. I don't believe it's something to do with driveline.

Cheers!