Makita MAC5200 Electric Powered Air Compressors Logo
Posted on Sep 27, 2010
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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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John Trevino

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  • Makita Master 1,420 Answers
  • Posted on Sep 28, 2010
John Trevino
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Joined: May 17, 2008
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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 www.toolpartsdirect.com or Lowes in the plumbing department good place for orings and silicone lube. Good luck

  • 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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2answers

Makita MAC5200.Brand new.Just broke-in. Pressure goes to 140 PSI and stops.Tries restart at 110 PSI.Motor"Humms"only.Will not restart until pressure below 20PSI.

http://www.toolpartsdirect.com/makita-mac5200-3-0-hp-air-compressor.html
There is a part called an unloader. It reduces the pressure on the compressor when the unit stops at the desired pressure. The actual unloader may be part of number 50 in this diagram.
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Some pressure switches can be adjusted with an allen wrench. You can't get more pressure from the regulator knob of the pressure isn't in the tank. look at the pressure switch with the cover off. If you see a screw with a spring around it. turn it clock wise 1/4 turn at a time until 125 is reached. The motor will labor more, so 2 hp may not be enough.
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I have a Makita MAC5200 and the guage is showing 120PSI , tank has pressure, yet I can't get any air from valves. Any suggestions would be appreciated.

Plunger inside the regulator could be stuck or adjustment knob stripped. Let the air out of the tank and take the regulator apart, lube with light grease (no kit available for this reg.). The factory part is expensive so replace (if needed) with generic, careful with size however because there is not much room under the panel and between the gauges . Easy temporary fix. Remove the safety pop valve and install a tee (or check under the pressure switch for spare port) re- install pop valve on the tee fitting. On the second port of tee fitting install a quick connect valve for full pressure. Generic regulator is sold at Lowes that can be installed on the temporary port.
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It sounds to me like your regulator is shot. It is the knob you have been turning in the (-) direction. The gauge reading 120 is the regulated pressure and the gauge reading 130 should be the tank pressure. You can find a new regulator from any Ace Hardware store.
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Mikita 5200 air compressor leaks air

Its likely an o ring inside the valve asembely one of the knobs has an air bleed to regulate the amount of pressure between the tank and the oressure that you set to come out the hose .You should be able to disasemble by eighter unsrewing the valve all the way out or removeing the knob and loosening the nut that holds it in and replaceing the o rings that you should be able to match up at a hardware store
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Will only build pressure to 100psi of rated 140psi

Chances are that the pressure switch, were you turn the compressor on and off, is bad. When they go out, they no longer build pressure to the regulated level you are looking for. If you haven't already, try turning up the regulator, if no more than 100psi build's, then it's a sure thing, bad pressure switch.
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My knob assy (137-0001) keeps popping off and air leaks around the adjustment knob on the top of the assembly.

SOMETIMES YOU CAN TIGHTEN THE OUTSIDE OF THE REGULATOR UP A LITTLE. OR THE REGULATOR IS BAD. OR THE REGULATOR IS SEEING BACK-PRESSURE JUST AS IF IT WAS INSTALLED BACKWARDS. DO YOU HAVE IT CONNECTED TO ANOTHER COMPRESSOR DOWNSTREAM THAT COULD POSSIBLY BE A LITTLE HIGHER PRESSURE AND BLOWING BACK THRU THE REG. HOPE THIS HELPS, JODY
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Usually you cannot adjust the cut out pressure of the tank/motor itself, this is why they have regulators, which regulates the pressure flowing down the air lines (regulators like these dont regulate actual tank pressure cutout). To regulate air flow using the regulator knob, you actually have to have air flowing through the hose while you make the regulator/pressure adjustments as regulators regulate pressure DOWNSTREAM from the actual regulator itself.. so air flowing through is a must. Attach an air blower or something similar and let air start flowing through the hose. Now turn your regulator knob in the "-" direction to decrease regulated pressure. It is best to bring pressure all the way down to "0" first, then open the regulator up (by turning to the "+" side) and pressure will rise until you get to the desired pressure needed for the air tool in use. The tank pressure will still be between 80-125 PSI as the motor regulates and keeps the pressure in the tank between these values automatically, but your line/hose air flow pressure will remain at the regulated pressure (say 40 PSI or whatever you set using the regulator knob).

Hope that helps and makes sense.

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