Compressor pump and air backflow?

by Cory

DeVilbiss. - compressor pump and air backflow?

I just recently tore the compressor pump apart to replace a broken bolt on the connecting rod. Reassembled just fine using silicon gasket instead of originals (all torn apart).

Compressor builds pressure fine, but when i shut it off, air flows back through the pump and out of a little hole in the top by the valves and air filter. I can only assume I reassembled something wrong?

I should mention this is a 2nd hand compressor that was given to me "needing repairs". It is a 6.5 horse 60 gal. DeVilbiss.

I'd much appreciate any help you could give me.
Cory, the first thing I would do is pull the tank check valve, clean or repair or replace it, and reinstall.

I suspect that some debris may have become lodged in the seats, and that may be what is allowing the air to bleed out of the tank when the compressor is off.

The other thing that I think might cause this is if there were a valve plate in the pump, and you inadvertently reversed it when you reinstalled it.

Did either help?



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May 02, 2012
check valve did it
by: Cory

replaced the check valve and that corrected the pressure loss issue. Thanks for the help...

On a side note, after this fix, it was only pumping up the tank to 70 psi. Error on my part, always make sure when using silicone basket material to separate your intake and outlet valves on the valve plate ;) Not even thinking i just sealed around the outside edge and this caused the issue. redid the valve plate gasket and works like a champ now!

Thanks again for all the help!

Apr 21, 2012
air leak
by: pcbeachrat

Does this leak continue or does it just give like a second or two of air releasing then stops? if it stops in a second or two then leaks no more then I would look at how the unloader valve is piped in/out and may be perfectly normal and what it is supposed to do.If it is a constant leak of air,then as Bill says,it sounds like the check valve is bad,or a small piece of debris may be lodged in it.As cheap as check valves are,if this is the case,I would simplly put a new one in verses trying to clean the other,for you may damage the oring in it or other seals some have...If careful they clean easily,but thats just me,if a part is pretty inepensive,i just replace them,then saved the used one for emergencies if they will clean up.

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