I have an '85 760 turbo that is having a problem with the turbo system. Whenever the gauge goes into the boost mode, you can hear a whistling noise that gets louder with increased boost. It is pretty obvious the turbo is spinning up and providing boost. The gauge shows plenty of boost--almost goes up the red, but stays in the high yellow (ok boost) zone. When it is in this mode, the engine is running very rich, pouring out lots of black (gasoline) smoke. And when this is happening, the car can't get out of its own way! Drive it very lightly and it runs OK. The problem has been getting progressively worse over the last several months. What I am pretty sure is happening is that there is a major leak somewhere in the compressor output (boost) side--the turbo runs up, moves plenty of air, the mass airflow sensor thinks it is really putting lots of air into the engine, so it delivers the appropriate large amount of fuel. Problem is, the engine isn't getting the air--it is leaking out. My problem is that I cannot find where such a leak is!! I've tried soaping down the entire boost side of the turbo system and putting it into its failure mode, but did not see any bubbles, though I had to run it and look when I stopped. I also removed the intercooler and pressurized it with my shop vac while soaking it with soapy water--still no symptoms. The intercooler had several tablespoons of oil which would indicate some compressor seal leakage, but I think it has been some time since it was drained. I've checked all hoses, etc.--No signs of tears, leaks, or looseness. Any ideas? Has anyone encountered this problem in the past? Thanks in advance. Lew Barton
Look on the underside of all the big hoses from turbo to intake manifold. The often fail where the oil pools. It's best to remove the hoses and poke at them with your fingers. -- Mike F. Thornhill (near Toronto), Ont. NOTE: new address!! Replace tt with t (twice!) and remove parentheses to email me directly. (But I check the newsgroup more often than this email address.)
First thing I'd check are the short hose pieces between the intercooler and the metal pipes. Really you should remove all the rubber hoses between the turbo and manifold and inspect them carefully by hand, there's only a few so this isn't a particularly big task. Press on them from the inside with your fingers and make sure there's no flaps opening up under pressure.
Thanks to Mike F and JamesSweet! I found the problem--it was a slot about the size of a dime in the bottom side of the hose that goes between the intake manifold (throttle body) and the pipe on the driver's side that comes from the intercooler. The oil pooling was right on--the hose is rotten on the inside, softened by the oil. The way I ended up finding it was to remove the top of the air cleaner along with the mass air sensor. I connected the hose from my shop vac to the hose going into the compressor, so it pressurized the entire turbo system, and the gauge showed a slight boost pressure. That showed the leak quite clearly--air was rushing out. As a temporary fix, I applied a tire patch to the ouside of the hose and wrapped it well with electrical tape. The car gets up and goes now!! I'll order a new hose to make the repair permanent. Thanks again for your help! Lew
Glad you got it solved. I still highly recommend inspecting the rest of the turbo hoses, that one rotted out and failed, others are likely not far behind.
