Overboost Problem, Wastegate Replacement

[SPARTAN GOLD]

Hey guys had a few issues with my BA XR6T overboosting, took it to a tuner and had the diagnostic pc hooked up, displayed an overboost fault code, the issue was the car shuddering at high boost when seccond gear was engaged, watched on my boost guage and turbo would boost from 7psi all the way up to around 12 then the pc would retard timing to prevent a big bang. I am a mechanic by trade and even I had some trouble diagnosing this one, to confirm a faulty wastegate acuator remove the vacume/boost line to the acuator and blow into the chamber you can do this while it is still mounted to the car, I just layed underneath the engine and did this with ease, if your lungs can force air past the diaphram then it is split, on a new one you will be blue in the face and will not be able to force ait into the chamber

[ratter]

you should not be able to blow air with your mouth through the actuator.

[SPARTAN GOLD]

Oil bypases the PCV and gets into the intake this then gets into the compressor housing and forced into the wastegate acuator diaphram this corrodes the rubber and the split slowly starts it gets bigger with time slowly allowing more air to bypass and here by boost pressure increase I managed to replace the wastegate actuator with the turbo still on the engine NOT RECCOMENDED it was a nightmare to replace the c clip on the flutter valve arm!!! to my shock horror after repair it still did the problem intermitently!!! cleaned out the boost controller and the overboosting stoped! this made me a happy man =)

[SPARTAN GOLD]

Both the acuator and boost controller are common problems with these cars, wd40 or carby clean will clear up the sludge in the boost controller, replacement actuactors can be bought online or at places like GCG turbos in sydney, the replacement part is far stronger but still can only take approx 13 psi.

[SPARTAN GOLD]

you should not be able to blow air with your mouth through the actuator.

Yes when there is a split in the diaphram you can blow air past it, hence why the turbo overboosts, pressure does not build up against the diaphram to open the flutter valve/wastegate.