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Air Compressor Oil Breather / Crankcase Breather Cap Buying Guide

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Air compressor oil breather elements allow air to be pumped within an air compressor system cleanly and efficiently. They then keep the compressor and air tools being used to run smoothly and at their peak performance.

I will provide you with some air compressor oil breather replacement products that could be suitable for your air compressor!

Table of Contents

What Does an Oil Breather Do?

To keep it short and sweet, an oil breather, or otherwise known as a crankcase breather, allows air pressure to be vented out from the crankcase so that a blowout of oil does not occur when the oil is being pressurized in the compression process.

For instance, in a piston compressor, the movement of the pistons and the clearance between the piston rings and cylinders allows some of the pressure created in the cylinders to pass into the crankcase.

Therefore, with the crankcase being a sealed chamber, a breather is needed to relieve the pressure to ensure this oil doesn’t cause a blowout.

Oil Breather Buying Considerations

Oil breathers are vital in the clean and efficient pumping of air within an air compressor. When needing to buy a replacement, always look to your manual first, and if you can’t do that then contact your manufacturer. Please don’t be thrown off by the fact that they go by a few different names:

  • Oil breather
  • Crankcase breather
  • Vent cap
  • Breathing rod

You will find these parts readily available online under combinations of all these names listed. It appears you can purchase a generic replacement crankcase oil fill breather vent cap and it will be suitable for your air compressor. However, please check with your compressor manufacturer before doing so as they may provide their own specific products.

Some replacements may be specific to certain makes and models whilst others will act as generic replacements that can be screwed onto almost any compressor with ease – as long as it’s the right size thread!

Oil Breather Available on Amazon

I have picked out a few generic replacements that are readily available on Amazon and may be perfect for your needs.

The first is this air compressor breather rod 15.5mm engineering plastic breathing nozzle valve applicable for most piston-type air compressors. This vent cap boasts a compact structure and is easy to install and use.

The second is a Colibrox VH901100AV air compressor oil fill breather is an OEM that fits Campbell Hausfeld VT or VH series, Husky, Sears, and other compressors. Easy to screw on by hand in seconds!

The third, an anti-aging air compressor breather vent cap, provides stable performance and long service life for most piston-type air compressors.

Oil Breather/Vent Cap FAQs (Frequently Asked Questions)

Compressor Pump Blowing Oil Out of the Breather Hole

by Johnny
(Cedar Bluff, VA)

I have an older model Speedaire air compressor with a Speedaire 2Z499B compressor pump.

I let a friend 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.

Air Compressor Pump Blowing Oil Out The Breather Hole
Air Compressor Pump Blowing Oil Out The Breather Hole


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 the compression stroke.

As to parts, please visit the home page, click on the Speedaire link in the navbar, and follow the guidelines to locate 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.


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


(Photo is uploaded above – moderator)


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.

Additional oil reading:

If you have any questions regarding air compressor oil breathers, please leave a comment below, with a photo if applicable, so that someone can help you!

By Bill Wade

About Air Compressors has been helping folks with their Air Compressor Problems since 2002 online. We're a community of DIY and Compressed Air professionals who are keen to support everyone across the globe with their air compressor issues and troubleshooting. Whether you're trying to identify an old air compressor, or troubleshoot an error code on a sophisticated new industrial air compressor - the community at About-Air-Compressors.com is here to help you