Oil spilling out of compressor.

by Bob
(Hobe Sound, FL)

The plastic combo oil filler/dipstick with crankcase breather on my little 2.5 gallon Harbor Freight compressor was cracked and falling apart.

I put a collar and epoxed a reinforcing cap on it, then I re-drilled a new breather hole to intersect with the old.

I ran the compressor, later noticing a growing puddle of oil underneath.

I can't see where from just yet. In re-examining the repaired cap (since that was the last thing "fixed") it seems possible that the new breather hole was inadequate or blocked by drill swarf. If that is the case is it likely that oil leak came from the crankcase oil seals due to a build up of crankcase pressure?

If so, are these seals easily replaced or should I just get myself a new $89.00 compressor?

This compressor has not seen much use and should have lots of life left - normally.


Bill says....

Bob, "easy" is in the eye of the doer. What's easy for you might be hard for another, and since I don't know your capabilities, I don't know if re & re seals would be easy for you or not.

Certainly time consuming, and you will make quite a mess as you pull the sump apart to find, and replace seals.

Your premise about seals may not be correct. While there is some migration of air into the sump past a leaking cylinder seal, I understand that the vent hole is there to allow outside air into the oil sump to replace oil that has been "used" and stopping a vacuum from being formed.

You will have a time trying to get Harbor Freight air compressor parts too.

However, if I had the time, and the workshop, then
I would certainly tear it down if for no other reason that to see what's what.

Odd that the oil fill dipstick cap cracked on an air compressor with so little use as yours did???

$89.00 compressor, when we buy one of these, we get exactly the value we paid for.



Comments for Oil spilling out of compressor.

Click here to add your own comments

Oct 27, 2012
Run Capacitor Exploded
by: Anonymous

My Harbor Freight Model 90234 also trips the thermal circuit breaker after running up to where the tank air pressure exceeds 70psi. This model has a cap-start cap-run split phase motor. The start capacitor feeds the second winding to provide starting torque, the run capacitor feeds the same winding to provide improved breakdown torque at speed. When the run capacitor fails, the compressor motor has poor breakdown torque, falls below the normal speed range, draws excess current and trips the breaker. (You may even hear it falling back into the start capaciotor through the centrifugal switch.)

Under the shroud, there is a centrifugal switch inboard of the fan blades. Under the motor are two capacitors stud mounted to the frame. The one with no terminals and only two wire leads is the run capacitor. Mine had exploded like a science fair volcano with simulated puffy lava, and electrolyte and oil dripping down the compressor casing.

You can get a replacement cap from Harbor Freight, but since the original part clearly doesn't meet USA / UL safety standards, you're better off getting something from a supply house with proper safety vents. I'd suggest changing the start cap at the same time. I found the .250" quick connect terminals had been soldered in place. Don't desolder them, cut them off and crimp new ones on. Don't solder them on the new capacitor, you're more likely to overheat the capacitor than add significant reliability to the mechanical connection. (If the mechanical connection is loose the solder will fail quickly under vibration anyway.)
Dear anonymous... an excellent, informative post. Our thanks.


Click here to add your own comments

Add your own question or comment. It's easy to do. How? Simply click here to return to Harbor Freight Compressor Issues.

Pressure setting

by Charlie
(New Bern, NC)

I have the 3hp model of the same compressor. From the factory they come set a about 100psi instead of the advertised/rated 115 or 120psi. There is a black plastic cover above the pressure guages with one screw holding it. Remove the cover and turn the large black screw clockwise to increase the static pressure up to the rated pressure. Use both guages to verify the pressure, then replace the cap.



Very carefully!!!!


Click here to post comments

Add your own question or comment. It's easy to do. How? Simply click here to return to Harbor Freight Compressor Issues.