oil level sightglass leaking

by BT

Has anyone been able to fix this problem?

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continuously running

by Keith
(Newtown Square, PA)

I inherited two Speed Aire compressors from a neighboring business (they were in the trash!)

Both motors run and build air pressure.

On one the gauges don't register pressure and it runs continuously.

Switch problem? The other the gauges work but it takes a long time to build to capacity, this is an older model. The first unit is a 4B227C the second is 3Z355H. Suggestions?


Probably a good reason they were in the trash, Keith.

There are a number of reasons why an air compressor will keep running.

One is that the pressure switch is pooched. You'll know if this is the case as the pressure in the compressor tank will build past the normal cut out and eventually the rising pressure will blow the PRV open. If this is happening, don't run the air compressor until you replace the pressure switch.

I think, though, that both your "free" air compressors are having problems with building air pressure, which is why they run, and run, and run but don't build pressure in the tanks.

Problems could be with the intake valves, pressure valves, piston seals... to name just a few.

See the troubleshooting section on the sitemap page for links to pages about why compressors run and don't build pressure, and things you can do about that.



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Speedaire 3Z189B has sat idle for years.

by Dan C
(Lansing, MI)

My Dad purchased this compressor in the mid 70's. the model on the compressor is 3Z189B. the model of the 2 cylinder block is 2Z262B.

It sat for 15+ years.

there is dried oil from the crankcase all over the top of the mounting plate.

I am concerned that an oil seal is flawed and don't want to start it up until I know there is lubrication and I am not going to destroy the unit.

what steps do I take to make sure the unit is functional.

is there likely repairs (oil seals, head gasket etc) that may be the cause of the oil leak?
That's a tough one to comment on, Dan, since I cannot see the actual unit and cannot find an image to help me understand the condition.

Assuming it's got an oil fill tube and a sight glass or oil dip stick, make sure the compressor is full of clean compressor lube oil.

If you haven't opened the drain in the tank bottom yet, do this, and examine what comes out, if anything. Badly rusty water is not a good sign.

Clear off the dust and debris over all the compressor and cooling fins.

If it is belt driven, slack off on the belt so you can see if you can turn the pump sheave by hand, after you have seen to the oil.

Turn the motor sheave too to ensure that the motor hasn't seized.

If everything turns / works, then if this were mine, I'd fire it up and monitor the tank gauge.

As soon as the tank pressure hit 20 PSI I'd pull the power, and examine the compressor to see and hear what I could. I would also open the tank drain again and let the 20 PSI air blow out any debris, if any.

All good, start it again and run it up to 30 PSI and examine again.

This would be a good time to operated the PRV to make sure it will let go when needed.

Keep increasing the pressure slowly until the compressor reaches normal cut out.

As a word of warning, there was a recent post on this site from an owner of a compressor that, like yours, had some years on it and was idle for many of those years. The air tank on this compressor exploded under pressure due to, I believe, rust weakening of a weldment along the bottom of the tank. You can see the results in the photos he included in his post.

Good luck,


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