Mac2400 leaking air at oil breather hole

this is leaking valve . you will need gaskets valve plate valves, valve seats .
Call 877-346-4815 they will help you the required parts.

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https://www.ereplacementparts.com/makita-mac2400-25hp-1720rpm-air-compressor-parts-c-97_1547_7559.html


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Piston Rings or Seals have failed.

Why does oil come out of the oil fill tube? ' About Air ...

https://www.about-air-compressors.com > why-does-oil...

It won't build up any more than 40 psi. ... I have oil blowing out of the oil breather on the pump. ... worn, and you are getting oil blowby into the air pressure chamber as the compressor runs. ... Doug in s.d.ca on Identifying An Older Air Compressor; Doug in s.d.ca on Craftsman upright air compressor slow starting and blowing ..

I have read both your questions and after taking both into consideration it sounds like it needs new piston rings. On a gas engine it is called blow by but both have a piston with rings on them, as they wear the end gap gets bigger and bigger allowing compressed air to bypass the rings into the crankcase where the oil is, the breather is there to allow air from the room to enter and exit as the piston goes up and down to avoid pressure or vacuum in the crankcase, the air on the top side of the piston is supposed to go into the tank but in your case some of it is going around the piston rings and into the crankcase building pressure and blowing oil out. There is not much inside a compressor like a gas engine, taking the head off and the oil pan should let you take off the connecting rod bolts and push the pistons out the top. This answer is based on the two comments of cant build all the air pressor and it is blowing oil out the crankcase breather. If you hit the 80 psi and unplug the compressor can you hear air coming from the limit switch box that the power cord goes into ? I will wait for your answer to continue.

Check for a leak between you compressor head (pump) and your tank. Your pump output may be good but as your tank pressure gets higher the leak will not allow the tank to build up.

Hi, my name is John. Welcome to FixYa. Check that you don't have a split line from the pump to the tank, also air hoses,exc. any kind of air leak, check and clean breather, if that does not help, then you are not getting any intake. Thanks for choosing FixYa. ... John

First if it's brand new I'd take it back to where you bought it. They have to sell you a product that works and anything you do to it will either void their responsibility or the company warranty. That said; if you have no leaks and assuming the hole you're talking about is the input side for the air filter and not the output side of the pump that should have a tube running into the tank stand pipe, it sounds like you may have one or more broken reed valves or bad ring(s) on the piston. Oil-less air pumps have one ring or wiper that does fail, oil-splash pumps have pistons like small engines with compression rings and an oil wiper. If they are run without oil the damage can be catastrophic. Not hard to fix but if you break the paint on the head bolts you void any warranty you have on the unit.

Your compressor should fill within 5 min or so. Here are a few things to check. As compressor is running check all air connections/fittings with soapy water (including regulator, drain fittings and quick connects). Repair as needed. If no leaks, unplug compressor and listen for air leaking from check valve at tank (remove 1/4 airline at checkvalve, brass valve at tank). Replace checkvalve as needed. If no leak at checkvalve, problem most likely valve plate in head of pump. The valve plate has two reed valves that sometimes break. Bad reed valves will cause compressor head to become very hot and discharge air will be hot. Replace as needed. Parts are available at www.toolpartsdirect.com. Good luck.

sounds like the regulator is fualty.

Send it back Right now do not keep iT NO IT SHOULD NOT BE LEAKING LIKE THAT Paul

Many craftsman compressor are built by champbell hausfeld using a dry type of cylinder and piston (no oil, no crankcase). If dry type, check for worn cylinder and piston ring. Pieces of the vinyl ring can jamb between the reed valves in the head causing air to escape from the intake. If your compressor has a crankcase and oil, check for broken reed valves in head. Spray soap solution on hoses, checkvalve, drainvalve, and fittings to check for leaks. Most likely problem is reed valves broken or open. Parts are available from sears or match parts to chpower.com. enjoy