Question about Makita MAC5200 Electric Powered Air Compressors

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Makita MAC5200 Compressor. Leaks air around the regulator screw in adjustable black knob only when I turn up the regulator pressure to allow air to flow through to the quick connects. I've taken the regualtor apart and it seems quite simple and there does not appear to be any faulty parts. Question: Is there some sort of seal I'm missing on the indise/underside of the black knob that prevents air leakage from the under side of the regulator knob when you screw it in?

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There are two types of regulators used. One has a rubber diaphram sealed at perimeter with body and a piston type. Most likely you have the piston type. Remove body containing piston/ spring mech. Examine piston lip seal. Lip will face toward body of reg. and must fit snugly into cylinder. Make sure cylinder is smooth and is well lubed.
If seal/piston fits loose remove seal and wrap some teflon tape in groove and re-install lip seal /test for snug fit. Notice small metal actuator extending from center of reg. , if it is circular (about 1/8 dia) then there should be an oring of the same size mated/fit into the piston. If this oring is missing it will leak as you describe. Lastly, there should be a gasket or oring sealing outer shell to body. If you have diaphragm type look for holes, tear or shrink too small. Parts are at or Lowes in the plumbing department good place for orings and silicone lube. Good luck

Posted on Sep 28, 2010

  • mintonrob May 08, 2011

    The above solution was very helpful. But I made the mistake of allowing the regulator assembly to spring apart when I removed the 4 screws of the casing. And because I didn't see how the parts were stacked/assembled it took me 3 attempts to find the right combination when reassembling. But once it was disassembled, I cleaned and lubed each part thoroughly. It took me longer than it should have (appx. 2 hrs) but it saved me about $70.
    Wrapping the teflon tape in the grove underneath the lip seal on the piston (as mentioned above) did the trick. And it saved me having to hunt down a new lip seal/o-ring. Love my Mac 5200, she's a workhorse. But I think leaving it idle for several months allowed the gaskets to dry, move,and warp. I'm leaving some pressure in the tank overnight, maybe this will awaken this gasket. Thanks again to PC_Tech50 for the solution!



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Hope that helps and makes sense.

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