First post. Please don't kill me.
Hello.

I just purchased an 760 Turbo Wagon from 89. It has the usual issues with OD relays, sagging headliner, drained A/C, and warped front discs. This is all fixable.

The turbo, though, baffles me completely.

Below is an attempt of a symptom description.

MPG: 10-12.

Turbo gauge hits 12 o-clock immediately when I touch the gas pedal.
If I keep the gas pedal pressed down, the gauge progresses into the middle of the white field (1:30-2:00) within 2-3 seconds. A hiss is also heard, which I believe is the wastegate.

There is, however, no turbo effect whatsoever. If I put the shift lever into 1 and slowly press down the accelerator to make the turbo gauge climb, I acually lose a small amount of acceleration when the gauge passes 12 o-clock and the wastegate starts to hiss (which it does exactly at 12).

There is a small lateral (radial) play in the turbo shaft. Nothing big though. Some oil sweat around the turbo, but not dripping in any way.

The intercooler and hoses surrounding it is new. I tightened up all the clamps to be on the safe side. No obvious leaks detected.

The hose going from the MAF sensor (just after the air filter) down to the turbo intake was rotten at the turbo end due to oil contamination and was probably leaking. I fixed it temporarily with duct tape for now . (The 10-12 MPG was measured prior to this fix.) The fix did not change turbo's behavior in any way.

The small hose from the turbo to the intake manifold is not clogged.

I have not checked if flame trap and oil separator is clogged.

I have not checked if the cat is clogged.

I have not checked the fuel filter.

Air filter and spark plugs looks OK.

Apart from this the engine works fine. Starts nicely when cold and warm. Idles evenly. No weirdo noises. No stuttering or other misbehaviors.

And now the question:
What is wrong with my turbo?

Thanks in advance for any tips and hints!

/Magnus Feuer.
Costa Mesa, CA.

Blessed be duct tape!

Found a massive leak on the connector hose between the intercooler outlet and the tube going to the intake manifold. I easily gained 50-60 HP on taping it up.

Thanks for your tips.

My weekend fun now includes cleaning out the flame trap.

/Magnus F.

..."The intercooler and hoses surrounding it is new. I tightened up all the clamps to be on the safe side. No obvious leaks detected.

I would venture a guess that the hoses weren't new, since you found a large leak in one.

Thanks for your replies.

I will do a deeper leak search this weekend.
When I went up to DMV yesterday to transfer the title, they shocked me badly by requesting a smog check...
That will be very interesting indeed.

/Magnus F.

gday Magnus,
i dont know too much about turbo's but im having the same kind of problems with my 87 turbo,when i trick to accelerate the boost goes up but nothing happens until u back off then it gets its kick. im getting new hoses for the turbo and my car has only recently just started spluttering and coughing so im replacing the fuel filter or fuel pump or the relay switch depending on what the volvo mechanic find out. ill keep u posted if i have any success
brownie

I had a similar problem on my 744t. I found two large holes on my intake hoses. Duct has held very nice (new hoses are on the way). Sounds like you still have a leak on the intake. It could be anywhere from the airbox to the intake mainfold. Make sure to look on the underneath sides of the hoses and definately look carefully at the complicated batch of hoses around the turbo. Don't tighten them took much around the intercooler. the intercooler has plastic inlet and outlet pipes. Have you read the 700/900 faq? it is a wealth of info.

Wastegates don't hiss.
The sound is a leak in the pressurised side of the intake(after the turbo); use more duct tape.