I think whats called the unloader valve for my air compressor is very noisy when it releases air, kind of like a flapping sound similar to letting air out of a large balloon. Is this normal? Truck is a 19 freightliner, cummins n-14. The noise is so loud my driver opens the draincock so he can sleep.
air compressor question
Discussion in 'Trucks [ Eighteen Wheelers ]' started by seapup, Sep 15, 2010.
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unloader vavle is in the compressor which lets the aircompressor bypass the air. The purge valve at the air dryer, released the air from the dryer to the compressor. Not sure what you are meaning he has to open the draincock..
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This might help
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I'm not real sure on this because it's been several years since I had to work on the air system, so I've forgotten some of the componants and their names, however I've heard that noise your describing on other trucks before. I'm not sure what causes that. I guess the first thing I would want to know is the air purgeing out the air dryer or safety valve near the governor? If it's coming out of the safety valve on the governor/next to the compressor then you have blockage somewhere. If it's purging out of the air dryer and still making that noise then maybe the spring that closes the valve is getting worn? Sorry for the lame response. Like I said it's been awhile since I've had to work on the air system (knock on wood). I'll be curious to find the answer myself.
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by the replies so far it seems there is a governor in the air compressor system which shuts off the compressor when it reaches the set pressure. If that is the case, then my governor must be defective as the unloader valve releases pressure every few minutes while engine is running. This can't be good for the compressor. Any feedback on this is very much appriciated.
I think my driver is opening a drain valve on the air dryer to keep the unloader valve from making the noise.
I may be referring to the unloader valve wrong, but it what releases excessive air pressure in the system.
As a side note I do have a minor air leak somewhere behind the dashboard, I looked for ever for it, no luck so far.Last edited: Sep 16, 2010
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might be an idea to see if maybe you have a new leak that is dropping the air pressure--causing the govenor to to start the aircompressor up?
should be no drain valve at the air dryer--he must be opening srainvalves on the air tanks--and that will make the compressor run all of the time as well--because it isnt getting to cut off pressure
if your air dryer is purging all of the time--could be that it needs a kit -
Last edited: Sep 16, 2010
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i read on a diesel repair site that the safety valve should open at 250 psi.
Is it possible that the safety valve is bad as my gauges don't go above 125 -
I really don't know. Sorry.
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