My 1998 12 valve maximum boost pressure fell to 8 psi, with the expected loss of power. So I pressurized the system and found a leak at the joint where the turbo outlet connects to the metal elbow. This joint has no gasket, and when I had it apart it looked OK so I put it back together and made the clamp real tight. Then my boost (measured at the manifold) improved to better than 20 psi. That was a while ago. Now my boost pressure has dropped to 15 and I suspect the same joint. What do I have to do to seal this joint?

 

There should be a rubber o-ring in there.

 

That would explain it. I will disassemble and have a closer look.

 

The O ring is almost flush and square cut to the joint. No other leaks were found?

 

I pressurized the system to 20 psi and found only this joint leaking. It didn't seem like a big one and I was surprised such a small leak dropped my boost to 8 psi. If the o-ring groove is in the turbo side of the joint I missed it because I didn't look for it. I'll go to NAPA and get a new o-ring.

 

Tardy update. My loss of power was a clogged fuel filter. It needs changing sooner than 10 years? I was glad to find and fix the small induction leak.

 

A diesel running low on fuel is strange indeed- I was a mile away from the truck when my John deere 855 began sucking air, ran ok until I "asked" for power then it would simply not produce any but still ran glass smooth- idleed fine and all. Put fuel in and back to normal
Yes, I know silly mistake- I learned that the fuel pickup is about a inch above the bottom of the tank though

 

If the turbo or it's housing has been replaced sometimes just loosening the four bolts on the turbo that allow you to clock it will allow you to aline the outlet just a little bit so the connection is squarer and not under any stress.