Hello gang. In my 1996 C3500, turbo w/o intercooler. I think that my wastegate solenoid is starting to fail. I need some help in determining thats what it is. It appears to be an intermittent problem, some days the turbo is working and some it won't. What I'm wanting to know is what is the best way to determine what the exact problem is. How much boost psi should be showing on my gauge. And which is the correct solenoid to buy, some say with and without vent?

 

Your wastegate is controlled by a solenoid on drivers side that switches vacuum to wastegate as needed. They only produce around 10-12 psi. What I have learned is that the plastic tubing (paired tubing, 1 orange, 1 black) going from vacuum pump to solenoid valve and then to wastegate cracks/breaks. It's cheap to replace. If the solenoid were bad, CEL would be coming on and faults would be in history. GM pt# is 10236929 for vacuum harness, should be approx. $25. This is for non EGR applications. This is the only purpose of vacuum pump unless EGR is also on engine. It controls that too. Different harness for EGR and there will be 2 solenoids on drivers side valve cover. LMK if you have EGR as well. Can give that part# as well.

 

Thanks dieselrick, I will check into the EGR tomorrow and let you know. I inspected the vacuum lines and didn't see anything suspicious, but I will check them closer. The fact that it sometimes doesn't work is what made me think it it might be the solenoid

 

Like I said, if solenoid was malfunctioning you would get a check engine light. With engine running at idle, remove black vacuum tube at wastegate and check for vacuum, if not present, remove harness from solenoid and check for vacuum there. If not present, either harness is broke or vacuum pump has failed.

 

And if any of above were happening, it would be smoking like a SOB!