Sprinter van OM642 turbo making negative pressure??

Christopher Owner/Technician Glendale, Arizona Posted   Latest   Edited  
2010 Mercedes-Benz Sprinter 2500 3.0L (642.898) 5-spd (W5A380)
Won't Run Unless Cac Hose Disconnected

Hi everyone. This is a strange one. I get this van in with low boost code and turbo actuator faulty code, sorry, can't recall the exact codes this moment. I checked all the CAC tubing and hoses, I found a damaged o-ring at the turbo outlet, and a split CAC. I replaced the CAC, all the o-rings at the turbo and silencer, and replaced the CAC hoses. Start it up and it will not run. Disconnect left CAC hose (out from turbo to inlet of CAC) and it will run. As soon as I put the hose back up to the CAC with engine running, a vacuum sucks the hose onto the cooler and the hose tries to collapse and engine stalls immediately. Turbo actuator is moving, I can command it with DAS and I get actuation. Is it possible the actuator is moving the vanes beyond the normal range and causing the turbo to make negative pressure instead of boost pressure? I have never seen this happen with any VGT. I will mess with it more tomorrow, it has to be that the vacuum is from the intake side of the CAC, which would mean the turbo is causing a blockage somehow.

Albin Diagnostician
Leavenworth, Washington
Albin Default

With the turbocharger unhooked on the pressure side, will the turbocharger blow any air, or make any pressure when the engine at idle?

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Niall Owner/Technician
Stirling, United Kingdom
Niall Default

You don't have a squirrel stuck in the air cleaner side?

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Frank Manager
Chicago, Illinois
Frank Default

Hi Christopher, sounds like a filter-to-compressor inlet restriction , or possibly a restriction on the inlet side of the Charge Air Cooler? Are you able to blow air through the cooler?

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Marlin Technician
Estacada, Oregon
Marlin Default

Not very strange, really. There is a restriction, look for it. Disconnect the impeller inlet hose and retest.

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Eric Owner/Technician
Edgerton, Wisconsin
Eric Default

I think the vacuum you are feeling is from the engine side, not the turbo side. If the turbo was making that much vacuum you should be able to feel a lot of air flow into the turbo. It sounds like a plugged air filter or problem upstream from the CAC between the CAC and the air filter.

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Christopher Owner/Technician
Glendale, Arizona
Christopher Resolution

Well, I feel like an idiot....but it was dark out, I was in a hurry, and I was tired. There was a rag sucked deep inside the plastic tube between the air filter housing and the turbo inlet. I didn't see it in the dark last night, but today in the light of day I saw it. Thanks everyone. Gotta remember the simple stuff. Chris

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Marlin Technician
Estacada, Oregon
Marlin Default

Well, thank you for publishing your mistake for the benefit of others. Not all is lost. ;-)

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