Compressor pump blowing oil out the breather hole.

by Johnny
(Cedar Bluff,VA)


Ok let me try this again.I am talking about the thing the arrow is pointing to.

Bill answers...

Hi Johnny:

What a marvel a photo is. Now I can clearly see what it is you are talking about. I thought from your first question that we were talking about the black inlet filter we can see on the top right of the compressor head in your photo.

In terms of the hole (where you used to have a vent plug) beside the arrow in the picture, you can either visit your hardware store and ask for a vent plug (usually made of sintered brass) or visit your local fluid power shop and ask for a brass valve muffler that's the right NPT size to fit the threaded hole where your vent used to be.

Lubricating holes commonly have a vent plug since the lubricating oil / grease gets consumed in the normal operation of the unit, and if there were not a vent, then in time, the oil that was consumed would leave a vacuum, creating problems.

So the vent plug you need provides both a method for letting air and not crud into the lube area, and stops the oil from splashing out when the machine is operating.

The vent shouldn't cost more than a couple of bucks.

Hope this helps, and thanks for writing back in.



Original inquiry:

I have an older model Speedaire air compressor with a Speedaire 2Z499B compressor pump.I let a freind borrow it and he somehow lost the breather to it and now it blows oil out of the hole when running.I have looked all over the internet for a replacement breather for it but i have had no luck.Is there a way i can fix this or another brand breather i can use.Thanks for any help or suggestions.

Bill answers...

Hello Johnny:

When you talk about the breather hole, I'm understanding that you are talking about the air intake?

If so, I see that you've got two problems.

One, your air intake isn't protected with an air filter (which would normally be in the "breather cap") and two, what's with the oil blowing out the hole?

It sounds like you've got oil blowing by the piston seals, and then, the reed or check valve that's inside the intake port isn't working, allowing that oil to get exhausted out through the intake when the piston is in compression stroke.

As to parts, please visit the home page, click on the Speedaire link in the nav bar, and follow the guidelines to locating your local source for Speedaire parts.

I'm thinking you've got quite a bit more to be concerned about than just the intake cap though.

Good luck,


Comments for Compressor pump blowing oil out the breather hole.

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Oct 10, 2013
I have the same exact Pump
by: Chuck

I'm trying to find a Rebuild kit for mine But I don't know the make & Model for mine & Mine has that top Plate on top like yours I would appreciate any help with the info. thanks

Aug 06, 2010
by: Anonymous

there is not a cap or cover for the breather, it is just supposed to have a small mesh filter part number vt014500av...if oil is coming out, you have too much blowby and should replace rings part number IT398 ring kit

Jul 04, 2010
To Bill
by: Jim

I honed my cylindar on my speed air compressor and replaced compression rings and oil rings and intake and exhaust breethers. I still have oil blowing out the breether hole.Do you have any suggestions. I have not replaced the blowout breether valve yet.

Jul 18, 2009
Oil leak out through breather
by: Anonymous

Presently i am validating my new high speed(1435rpm) direct drive(5HP)compressor. i found within few hours of running oil is coming out of breather which is mounted on the end cover. Could you please give me possible causes of oil leak.


It's a bit hard to be sure from the little you've provided. If the unit is brand new, there might have been a bit of oil in the cylinder that's wicking out the in port.

If it persists, then you have a bigger issue. Monitor it.


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Compressor cut off

by Leon
(Brentsville Va)

I was given a air compressor that would not reach its max air capacity. It would run continuously and olny reach 45psi. I found a leak at the line going into the tank and made the repair. Now the tank reaches its peak capacity and will not shut off. It blows the safety valve and keeps running. I have a Sanborn Model # B07F350-13 Serial # P2800027. What do you think the problem is?

Bill answers...

Hi Leon:

My new ebook, being launched in a day or so (yes, it is that close) is all about The Home Compressor, and one of the things a great deal is written about is the pressure switch.

What the pressure switch does, how to diagnose problems, how to find a new one, and of course, how to change it out.

I mention this as I'm pretty sure it is your pressure switch that is pooched. And, you have a very dangerous situation here.

I recommend you not run your compressor again until you get the problem fixed.



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2HP compressor piston jam in the cylinder

by Max

Hi Bill,

Foremost Im not mechanical incline, hope you understand if I ask questions that even a kid could answer

I have 2 HP mounted air compressor that is use for sprinkler system. The motor coil short and when I investigate found the shaft of the air compressor jam.

I open up the oil tank and found the oil to have dark brown residue ( suspecting rust). Both the bearing at the shaft is un-movable. Both piston is jam/stuck at the cylinder.

Is piston jam/stuck normal? I tried to push or pull the piston but it wont bulge.

Is it normal to have rust accumulate at the oil, piston and shaft?

Any advice on the repair and future maintenance to prevent such occurrence?

Hope to hear from you!

Sincerely yours,

Max, yup, when you say "Is piston jam/stuck normal? I tried to push or pull the piston but it wont bulge." it sure sounds like the pump is seized.

You will quite possibly need to disassemble the pump to try to get it moving.

Drain the oil sump, and fill the appropriate level with compressor oil.

I expect you are operating this compressor in a high humidity and heat environment, so draining the compressor tank after every use is a good preventive maintenance step.

Make sure the oil is full to the proper level, and change the oil regularly.

If the rust has scored the piston in the compressor pump too badly, I suspect it's time for a new compressor. If you do get one, keep the compressor manual, and follow the maintenance instructions in that manual.



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Old Teldine diaphram compressor rebuild problem.

by Randy Fischer
(Electric City, WA)

I am rebulding an old compressor that i use for breathing air on a gold dredge. It is a teldine and is no longer made. being a machinist I am able to make most replacment parts, but the reeds are a bit of a problem. Is there any one that makes a genaric reed the one I need is .750 ' x 1.0625' .010" thick with 2 holes in one end with .4375" spacing center to center.

Bill answers...

Hey Randy, welcome to Electric City WA.

I don't know of any source. Maybe someone reading this post will know of one.

Meantime, could you not emulate the function of the reed valves by simply using check valves?



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