Boost drops off after warm up
 

1992 300D 2.5 Turbo
Just installed a boost gauge and I was correct. When first started and engine cool the boost gauge shows quick reaction and max between 12 -14psi under hard axcel, then after warms up to 80C, boost and car is now sluggesh and max around 8psi. Car has 161,000 miles indicated and is new to me. Any ideas?

Thank You
Phil

1992 300D 2.5 Turbo
1981 300CD No Turbo

I have the opposite problem. When I start the car cold in the morning (32 degrees), I have no boost until the car warms up for about 5 minutes, then bamm, boost.

How did you install your boost guage? I want to install one...

Bought a Vac / Boost gauge at Advance Auto aprox $38.00. On the intake manifold there are 2 allen head plugs, took out the smaller one and the gauge came with an adapter that was the right size. Easy & Done.... .

Phil

1992 300D 2.5 Turbo
1981 300CD No turbo

Check the wastegate and it's lines. Also, check the electrical connections on them.

Found the problem: The vac line going from the vac solinod with an arm on it mounted on the top right side of the turbo (waste Valve??) had a split in it on the bottom edge (very hard to see). Now the car makes 15 for an instant then drops to 12. It is now making the right amount of boost when it is supose to..

Hopes this helps someone in the future

Phil