I have a bostitch 6 gal pancake compressor that won't build pressure past about 20 lbs. when I turn it off I don't hear air leaking out anywhere and when it's running it runs at a higher pitch ( similar to a shop vac when it gets clogged) I was using it to spray wall texture so it was running pretty constant for about 20 min. before the problem occured. It was working fine when I started. had full presure 120 lbs. and I was running the outlet pressure at 60 lbs.

could be a possibility. Clanking or rattling: Loose internal mounts can cause rattling and clanking from the compressor. The sound probably means that the motor has come loose and is moving around inside the sealed compressor can

is it building up any pressure on the gauge
if the pressure recorded is around 40 psi or less , replace the failed poppet/reed valves in the compressor head
if it goes to 100 psi then replace the automatic controller for the motor

Hi, There are different posibilities. I would need more information. Was it always like that? Does the guage on the main tank and the guage on the regulator both not show more than 20psi? When the auto shut-off is triggered do you feel there is more than 20 psi in the tank?

Jim:
There is a leak somewhere... Use a soapy solution at the air tube from the compressor head to the tank (both ends) and at all air hose connections. The bubbles will tell you where the leak is and you can repair the connections from there...

Small leak will prevent the unit from building proper pressure. Check all connections with soapy water and repair as needed (including under cover). If no leaks are found check cylinder for scratches. Push piston to top of stroke and check walls for fine scratches. If scratched, pressure is leaking past vinyl piston ring. If no scratches or leaks, most likely reed valves, head gasket or combination of both. Easy test, with compressor running and attained 90 lbs, place finger over air intake and check for good suction (carefull could be hot) . If good suction, then air is leaking somewhere, of no suction suspect reed valves/worn cylinder, if air seems to be blowing out of intake, suspect reeds /gaskets. Good holidays

Oil free pumps do tend to blow the piston ring (not too expensive) available at searsparts.com. Remove covers to pump and manually turn crank until piston is at top and look at the condition of the cylinder neer top, If it looks scratched, order cylinder kit with piston ring. If it looks good and shiney, could be the valve plate in the head. There are reed valves that tend to break. Run pump however with covers removed and check with soapy water for air leaks and repair as needed (air leaks under the cover will prevent unit from filling). Good luck

PRESSURE REDUCER valve

Do you have a pressure relief valve. Take off the cover, make sure all fittings are tight and their is no cylinder head leak

sounds like valves in head have failed and need to be replaced, that is where I would start looking first.

Check to see if air is leaking past 'pressure relief' valve. It's probably leaking and that's where all the air is going.

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