overboost problem

[ornas]

Hi, today was my first try to run engine at higher revs after rebuild. Boost gauge showed 1.4bar. Waste gate is connected without any boost controllers. What can couse wastegate failure?

[tobluforu]

Is it frozen shut?

[ornas]

not sure, will try to give is some pressured air. will see does it hold pressure or not. Is there any kind of membrane inside of something that could be worn? or can it get stuck just because of lying for 2 year without use?

[spuggy]

Originally Posted by ornas

not sure, will try to give is some pressured air. will see does it hold pressure or not. Is there any kind of membrane inside of something that could be worn? or can it get stuck just because of lying for 2 year without use?

Diaphragm can split, also the owners handbook for the early, 3.0 930's states that you should, every time you drive the car, open the wastegate by using full acceleration through a gear to redline. Heh. Warning is that the valve can stick otherwise.

My guess would be either a split diaphragm or a seized/stuck valve; it's a pretty simple device

If I recall correctly, the top of the wastegate is just a vent; apply air pressure - gently! so as not to split the membrane - to the port in the body; valve should open. Do not use more than ~1 bar pressure.

Rebuild parts can be hard to find; used replacements might be easier - or Tial make two different 46mm wastegates that bolt on, one with shaved fins intended as a direct replacement on a 930, the other clears fine with aftermarket exhausts. Apparently. (I'm still using the factory one).

[tobluforu]

If it's been sitting for a long while then yes they can seize right up on you.