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Old 05-14-2014, 08:18 PM   #1
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Air Dryer Question

I have a Haldex PurEST air dryer on my 2008 Winnebago (with 6.7 Cummins ISB). If I accelerate from a stop at a pretty good rate, the air dryer makes a hissing sound until the rpm level of the engine drops when the transmission shift into 4th gear. While driving with a Cummins tech for an unrelated problem, he suggested the noise was likely from a faulty turbo saver valve in the dryer unit. Has anyone had a similar issue? Other than the hissing under acceleration, the air system seems to function appropriately.

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Old 05-14-2014, 08:46 PM   #2
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if it is hissing while accelerating only then I would think that you are loosing boost pressure. Possibly a air leak in the pressurized side of the intake. Check all the fittings from the turbo to the CAC and back to the intake of the engine. Spray the hoses with a soapy water solution and with the engine idling there is enough air pressure in there to show up an air leak. HTH Skip H.

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Old 05-14-2014, 09:43 PM   #3
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My 05 Journey does the same thing under harder than normal acceleration. It is coming from the air drier.
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Old 05-14-2014, 10:43 PM   #4
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Yes, it's air dryer, not boost, related. Acceleration also runs the compressor harder. Can someone tell me what the turbo saver valve (on the dryer) actually does.
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Old 05-20-2014, 08:13 PM   #5
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Patent US5334230 - Sealed air dryer with turbosaver valve - Google Patents
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Old 05-20-2014, 10:23 PM   #6
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If I am understanding this correctly the turbo saver is a valve that opens to let the compressed air from the compressor "Dump" directly to the atmosphere under high load (throttle) applications freeing up a few horse power. By letting the air compressor (free wheel) there would be less load on the engine. Makes sense?? If this is the case then I like it! Wish I had that option on my coach. You can never have too much horse power!

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