Boost problem; turbo dumps at 5 psi.

[93gmc6.5]

I have a 93 6.5 diesel and the turbo dumps all pressure at 5 psi, and will not gain again unless I let totally off the accelerator and clutch it. The waste gate is solid so I don't think that is the problem (as far as the spring is concerned). Is there any thing else in the actual turbo that can go bad with the waste gate? All hoses also seem to check out good. Turbo spins freely also. I am out of ideas. Please help!

[john8662]

So, the boost goes to "0" boost after it gets to 5psi?

Sounds like the actuator is bad, you'll need to replace it with a new one with a better spring.

This would be the perfect time to install a Turbo Master boost controller instead. This is available at www.heathdiesel.com

J

[Hubert]

Does it start pouring smoke when boost dumps? Could be gauge malfunction if not??

Seems like I've read the early GM-x the linkages or pivot shaft or somethink would wear excessively and cause issues (not sure what).

Can you wire the wastegate shut and test to see if it will build higher boost?

[93gmc6.5]

I have a mechanical actuator and I cut the factory one in half threaded the end and put another spring in there. I tightened the spring down so the actuator is no longer able to dump because it is the same as solid. It will still will not hold more than 5psi, so what else could there be?

[93gmc6.5]

Hubert you might be on to something with the pivot shaft. I have the actuator solid right now. How do I fix the pivot shat assuming that is the problem?

[john8662]

How do I fix the pivot shat assuming that is the problem?

You'll need the housing repaired, in short a possible turbo rebuild.

If the bushing is severly worn, it will cause the shaft to pivot, and that'll cause the wastegate flapper/valve to not seat, blowing your boost.

Just grab the wastegate shaft and wiggle and rotate it with the actuator arm removed.

[93gmc6.5]

I will try that thanks for the help.

[Mtrman]

I was in the same boat. My new 93 K3500 had a sloppy waste gate shaft. I did not want to spring for a rebuilt turbo until I put some milles on the truck.
I fixed the shaft with a 3/8x16 x 3" Stainless bolt from Ace Hardware. I think it cost me @ $.60 to fix. Just open up the bushing to 3/8 and use the bolt as the new shaft. Make sure you use a bolt that is not threaded all the way. I have 20 miles on the truck since replacing the heads and the waste gate is working great. If you want step by step details just let me Know. Mike

[93gmc6.5]

I to spliced a bolt on the old wastegate shaft so now I can tighten the spring down to whatever I want. I can even make it solid if I tighten it enough. The problem is that I have it all the way tightened and it is solid; I even put a vise grip on the arm, that goes in the turbo, to see if I could get any play and there was none. But it will still not hold anything over 5 psi. What does the inside of the waste gate look like could there be anyway that the shaft is flexing in there?