760 Turbo No Power, smoking, Leaking?

  • Thread starter Thread starter Lew Barton
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Lew Barton

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
 
Lew said:
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
Click to expand...

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.)
 
Lew Barton said:
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
Click to expand...

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
 
Lew Barton said:
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.
Click to expand...


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.
 
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