Air Compressor Oil Related Issues – Oil Damage To Compressors

Published Categorized as Air Compressor Oil Guides 14 Comments on Air Compressor Oil Related Issues – Oil Damage To Compressors

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There is fuel in oil reservoir?

by Rusty
(Cuero, TX)

Our compressor is mounted on a service truck. the exhaust is facing the front of the truck.

Ibelieve wind entering the exhaust has damaged the baffles. the compressor starts for only a few seconds, then coughs and dies. upon checking the oil, we found that a large amount of fuel had leaked into the oil reservoir.

Any suggestions on where to start in order to fix the compressor. Indeed, next time we’ll be mounting the compressor with the exhaust facing the rear of the truck! Things you learn…

Thanks for your help

Additional oil reading:

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I just traded for this 5hp compressor. It runs great and maintains about 150 psi and cuts on at 110 psi. I’m trying to determine what type of oil to use in the pump and I can’t determine how much oil to put in it. Not sure how to determine the appropriate oil level? It appears there may be a level check, but it also appears there is some type of plug inserted in this hole and I don’t really want to remove it – in the event that I’m wrong! The only markings I can find are in the… Read more »

You could read this, if you haven’t:

If the plug you’re talking about is the one near the bottom center of the first pic, or the between the HP (smaller) head and the output tube, near the the pentangle in the second, then yes, that appears to be where oil goes in. Usually the drain plug is lower in about the same place – can’t tell from these pix.
After you read the above and the page about changing oil, if you’re still unsure, come on back, maybe with slightly bigger/better pix.

Good luck.

I need to know how much oil to use on this air compressor pump, but I am having a hard time identifying it because it wasn’t on its original tank and there is only 1 set of numbers or letters on it that are to worn to make out. I have made a new gasket for it. Hope you can help!

Were you going to send some pix so we can see what you have?

Hi –
Did you mean to post some pix of it so we’d have some idea what pump you’re talking about? ?

Central pneumatic air compressor. I put oil in but the sight glass does not show any oil.

What’s the model number and do you know how much oil it is supposed to hold? How much oil did you put in that’s not showing in the sight glass?

I have this same problem, I believe I have well over filled my draper 3hp 100 liter (I’m in the uk) and the level doesn’t show in the sight glass. When I run the compressor it spits oil out of the filler cap which is a good indication its over filled but no reading on the glass.

I’ve uploaded a photo. Is this your compressor, Andrew?

Actually, it may have overfilled, but if oil continues to come out of the sump through the oil fill tube, I would suspect a major leak of air by the piston seal. They may have been damaged by the overfill, but likely, it’s a wear issue.

Can you feel air coming out of the oil fill tube while the compressor is running. If so, that’s a good indication of piston seal by-pass.

Hi, thanks for your response, yes that is my model compressor. Whilst the motor is running it is spitting oil all over the place, so yes there is oil and air coming out of the vent holes but once the tank has filled it doesnt leak any air. Do you have any idea why the level is not showing in the sight glass? It’s not that it’s over filled and the glass is full because I drained what little oil was in there and re-filled with a full litre of oil trying to get a reading and it just doesnt… Read more »

Doubtful there’s a blockage. The sight glass shows the sump level directly. I think that the two issues are not related. Issue 1; Oil out of the oil fill tube while the compressor is running indicates bad piston seals, and lots of oil means more air is bypassing the seals and venting out of the sump with the oil. You’ll want to tear down the pump and check out that. Issue 2; No oil showing in sight glass. I suspect that you have not filled the sump to capacity. Get the problem with the air leak fixed, then add oil… Read more »

Thanks bill, I will follow your advice and see how I get on.


Andy – a litre is a LOT of oil for the apparent size of that pump. Before you tear it down, I suggest you remove the sight glass. If there’s a litre of oil in it, I expect around a half litre will flow out. I don’t know how long you’ve had this, but I suspect the glass is dirty. The oil fill plug shown in the manual looks like it may also be sort of a dip stick. You could try wiping that and see if it gets oil on it when removed again. If so, it’s overfilled, from… Read more »

Hi, thanks for your comments the glass is slightly cloudy but not to the extent that I cant see anything through it. This may sound a little stupid on my part but in order to remove the sight glass, I need to remove the filler housing, which I think involves stripping the whole thing down. I removed the bolts and its stuck solid so tried some slight force but didn’t want to push it too far because of fear of breaking it. I have contacted the manufacturer to see if I can get the piston rings and head seals so… Read more »