Tested this compressor before disassembly. It was pumping air but not holding any pressure. This is what we found after removing the head and valve plate, you can see why. Exhaust flapper valve was broken (see pic). Intake flapper didn’t look too good either. Cleaned the inside of the compressor, replaced the intake and exhaust flappers with new ones. Installed new valve plate gasket, then we retested with great results. Pressure gauge showed higher than 40 psi, about  and held pressure. The pressure can be adjusted by the relief valve on the top of the head on some of the older T-80 models.  Unloosen the set screw on the top of the head and turn the brass fitting inside with a straight blade screw driver to raise or lower the pressure. We set the valve at 40 psi. If you are using a reserve tank, may not even have to set the relief valve that high, that will save wear and tear on your compressor.                                                                                                                                These T-80 compressors have been around for many years  and have proven to be very reliable. I personally have used mine for several years (weekend mining/dredging) without any issues. We have replacement parts here at Handle-Up.com available for purchase, send an email for information.