Losing air pressure in a Speedaire Compressor

by Walt
(Phoenixville, PA USA)

What would cause you to lose air pressure the Compressor?

Hi Walt...thanks for the question.

Many things will cause you to lose pressure.

From your question, I'm guessing that the compressor runs, brings the tank up to cut out pressure, the compressor stops, and then you see the pressure fall in the tank without actually using any air?

If that's the case, and there is no downstream leak of any kind, then I'm betting that the check valve going into your tank hasn't seated properly, and air from the tank is escaping back up the line to the unloader valve and from there to atmosphere.

Stick your head down close to the pressure switch and listen for a hissing.

If this isn't it, then I need to know more about loss of pressure.



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Need advice about an air leak out of a Speedaire's compressor tank.

by Connie

(Recently widowed and haven't a clue.)

Have discovered a small hole in the tank and am wondering if it would be dangerous to continue to use it as is??

If a tank replacement is the necessary fix....how do I determine what size tank to purchase?

This "old" Speedaire is Model #3Z355.

Certainly would appreciate any advice.

Bill answers...

Connie, first off, my condolences.

Second, my immediate response is junk the tank. A small hole is there because (I expect) rust has eaten through the wall of the compressor tank, and that weakened area is manifested by a pinhole (or maybe larger?) leak.

The tank is not safe.

To get information specific to your Speedaire compressor, click here and follow the links.

Are you in a position to do the work yourself? I ask this question as in the last few years, the cost of the home workshop compressor has plummeted faster than my bank account does when I go to the hardware store.

Decide what you need your compressor for. This page might help.

Then, if a small DIY type compressor will work, you might spend a whole lot less money buying a new one that trying to get the old one fixed. And the new one should come with a warranty.

I sure hope this helps.



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I need an answer on a Speedaire rebuild

by john montoya
(LA california)

Rebuilt a speedair air compressor-put in new rings and new intake manifold -pressure was initialy set at 110 psi--after 25 minutes pressure dropped to 70 psi and cannot be raised any higher. This is the 3 time in three days we have taken this compressor apart.

The 1st time it was rebuilt it lasted 1 day and the pressure slowly decreased to 0. When we opened it up one side was burnt and the o ring was damaged beyond repair, this was the port over the large piston.

Bill answers...

Hello John...yup, been there and done that with other pieces of equipment. Not much can be more frustrating than doing the same thing over and over, and still the %$#%^$# thing doesn't work.

While complex to take apart and rebuild, compressors are really simplistic devices.

If the pressure in your tank won't get past a certain point, and the compressor head is still chugging away, then there's a few things to check.

Consider that you've got a leak somewhere that's bleeding air off fast enough that the compressor can't get the reservoir air pressure past that point. Doesn't sound like that's your problem, but you have to make sure.

That the pressure in your compressor tank bleeds back down to zero when the compressor stops does suggest that you've got a leak somewhere. Either air is bypassing the piston and exiting through the unloader valve in the pressure switch, or the check valve in the line between the compressor head and the tank is flawed, and air is bleeding back up that line to the unloader valve exit. Or you've got a leaking fitting or hole in the tank.

In most compressors, as long as power to the compressor motor is off, the unloader valve is open to atmosphere.

If the pressure in the tank doesn't get past a certain point and the motor keeps running (and assuming that all components are running properly), then we're back to either losing air somewhere, or the piston can't generate enough ooomph to get more air into the tank. Why? Piston seal failure? Check valve into the tank is partially blocked causing back pressure over which the compressor can't compress air further, it's so hard to know John.

While I share your frustration, there's not much I can do to help identify the problem you've got in rebuilding your Speedaire compressor.

Good luck,


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