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'94 855 turbo CBP valve blown 850

Hello all-

I just spent Memorial Day weekend getting my rebuilt turbo back in my wagon (blown seals after 190K) along with new vacuum lines and crankcase breather lines. Cleaned all the oil off the motor too- amazing difference.

Now for the bad news. When testing the turbo before re-installing I noticed the integral compressor bypass valve on the Mits turbo made a hissing noise when applying vacuum, but no 'snick' like it was working. The Saab external plastic CBP valve I have on my bench from an abandoned 740turbo project makes the 'snick' when vacuum is applied. I'm guessing the CBP in the Mits was either bad before the rebuild or somehow damaged in the rebuilding process. Either way, I'm very pleased with the work Majestic Turbo of Waco Texas did for $325. New seals, bearings, compressor wheel, paint job, and they replaced the stripped stud I didn't even mention.

Having said all of this-

1- the turbo pulls wonderfully, but I occasionally get a high idle (1000+ rpm in Park), and sometimes the motor is a little slow above 3K rpm and then ROARS at 4K rpm. My brother has noticed this in his '95 855T. The high idle makes me think false air.

I am wondering if the engine's response (reminds me of my 740 Turbo, a little more lag than before the rebuild) could be related to a bad CBP valve.

2- Could I drop in the plastic Saab/Bosch CBP valve I have on my bench? I'm guessing I would plumb it into the charge air pipe that crosses the motor and back into the turbo intake after the AMM.

Any thoughts are welcome...

-Dylan







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