Blamb

07 SS/SC Cobalt. They keep saying it's the bypass valve but I just replaced it. I can't find any vacuum leaks anywhere. One day I'll have boost the next I won't.
The other day I noticed a noise I haven't heard before or just not pay any attention to it. Can the solenoid valve leak through the actual vent?? Or is just bad, cause it's pretty loud at time I think... I could be wrong. Help!!!

jdbaugh1

iTrader: (1)

So your boost is intermittent? How much does it very day to day? I would think if you had a problem with your actuator it would be consistent. The solenoid is not required to go into boost, it only acts to pull boost if the ECU tells it to. In it's resting state the spring loaded actuator has the butterfly valve closed and is in non-bypass "boost mode". The line running out of the top and into the neck of the supercharger will use vacuum behind throttle body to pull the butterfly valve open into bypass mode.

It could just be your ECU pulling boost for some reason. Are you throwing any codes? The way to check and see if your ECU is pulling boost would be to disconnect the solenoid line from the actuator and just leave the actuator bottom nipple open to atmosphere.