compressor problem... help

So my compressor builds to about 90PSI or so then it starts working really hard and sometimes stalls all the way out while the motor tries to push the pump, usually it will begin to pump for a second then work hard again.... WTF? its a Campbell Hausfeld VT6275 60GAL 5HP single phase. 220V.. I was thinking its either the Check Valve or unloader valve or both.. what do you guys thing?

It did it for a while but its getting worse and worse as the days go by.

Kinda sounds like a bad pressure switch

well the pressure switch does what its supposed to.. i have it set to turn on at 90 and off at 160....

160 sounds a little high to me..i think mines set at 125

i have mine set for 185 off 145 on...i like it fast...lol sounds to me like it may be getting hot and squizing the piston,have you tryed greasing it? most compressors even the selfoiling or nonoil kind need grease

im talkin about my shop compressor lol.

thats what i was talking about

me to....