Speedaire 3Z180 blowing oil into intake from the vent tube

by Adam Lewnadowski
(Mchenry, IL)

Hi, I just picked up an older but very clean Dayton Speedaire 3Z180 compressor.

I found the air filter to have a lot of oil on it and so I took it off and started the compressor.

It got up to 50 PSI and then oil started to push out of the copper vent tube that connects to the air inlet. It got worse and worse as the pressure in the storage tank built up.

Any thoughts on why the would be excess oil being pushed up like this? I took the cover off of the unloader and there was oil in there and the baffle up top. the baffle appears to be a thin piece of metal that stops oil that is slung off of the governor weights.

Any thoughts on what I should do? There does not feel to be a lot of blow-by and the cylinders look very clean when I take the valves off on look into the bores.


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May 20, 2018
Speedaire 3Z180 blowing oil
by: Doug in s.d.ca

> Could the weights be traveling too far?

Maybe - what RPM on the pump?

>How much oil should be in the unloader case?

Not much. Maybe somebody overfilled or tilted it.

Maybe just clean it up and retry...oh, you probably did that.

Let us know.

May 18, 2018
Speedaire 3Z180 new items
by: Anonymous

Thank you for the manual. I went through and checked the list on page 7.

None of those have helped unfortunately.

I went ahead and pulled the cylinder off of the pistons. It all looks very clean and nice. Good rings, smooth/hatched cylinder. Everything checks out visually.

I went ahead, put the compressor all back together and then tried something. I went ahead and took off the governor weights and ran the compressor. ISSUE FIXED! So what I have found is that the oil from the compressor gets into the unloader and the governor weights "fling" the oil around. Then, the small amount of blow by that the compressor has pushed the oil up the vent tube.

So, pulling the governor weights in my eyes is more of a test or diagnosis. It identifies what is causing the oil to get flung around and the slightly positive crank case pressure is what pushes the oil into the intake. Now, I need to figure out why the oil is being slung? The half-round baffle is in the unloader housing and in the proper orientation so I do not think that could be it.

Could the weights be traveling too far? How much oil should be in the unloader case?

May 15, 2018
by: Doug in s.d.ca

Yes. Download the manual if you don't have it, here:


Look at page 7 and check the things listed for "Pumping excessive amount of oil".

Let us know what you find, whether you fix it or not, please.

Good luck.

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