I recently purchased a 1989 Volvo 740 turbo 4 cylinder. While doing an oil change I noticed my wastegate was not hooked up, so naturally I hooked it back up. While going for a test drive I noticed higher boost (obviously) but under high boost conditions the car would cut out. I looked under the hood and found that my blow off valve had come off its bracket so I tightened it up and went for another drive. This time it would bury the needle for the boost gauge, blow off, then repressurize, and blow off again. The cycle will just keep repeating itself at anything more than slightly over half throttle. I went back under the hood and checked all of my hoses, they seem okay, no holes or cracks, and all fittings are tight. Where should I look next to resolve this issue?

 

I believe your wastegate is stuck causing overboost. I would soak the wastegate with Mouse Milk http://mousemilk.com this is what we use on aircraft waste gates...good luck

 

Agreed, if the hose going from the cold side of the turbo system (wherever it may be coming from, turbo to intake manifold) is in good shape and not leaking anywhere, or if you don't have a torn diaphragm. You can check if its stuck by trying to move it with wrench, your hand, or a screwdriver. If it moves, and the hoses seem good, you probably have a bad actuator with a torn diaphragm.

 

I can move the rod that hooks up to the trubo. Where else can I check to see if the wastegate is stuck?

 

See if you can move waste gate around with your hand.

 

With the rod disconnected I can move the wastegate easily, and can hear it close and open. With the rod connected I feel resistance from the diaphram.