Craftsman 106.175781 - unloader valve continuously leaking?

by Bruce
(Riverview, MI,USA)

Craftsman sears 2 HP air compressor

Craftsman sears 2 HP air compressor

I have a Craftsman 106.175781 2 horse twin cylinder 20 gal tank air compressor.


While in use the air nozzle blew off the air line.

I turned off the compressor to let the pressure off and replaced the air nozzle.

When I turned the compressor back on it would not build pressure. I found that it was leaking air at the uploader valve.

After searching Sears parts direct, that part was not available anymore. So, thinking it was a basic generic part I went to a few stores to look for a similar valve. There were a number of the uploader valves on compressors. But, where to purchase them is another quandary.

In info search I seen your site and read for diagnostics for the problem. You stated at one point that if the uploader valve is continuously leaking it is probably the check valve on the tank. My unit has a separate uploader tube from the head to the pressure switch and a tube from the head to the tank (where the check valve is).

At another point you mentioned that uploader valves go bad also. As I looked at the uploader valves on various compressors at stores I noticed that the needle pin protruding from them were basically in the more in position as display models and not under pressure.

My uploader valve's needle pin (off the compressor) is in the full out position and has light spring tension. Is there a simple basic check test to determine if the uploader valve is at fault or the check valve?

It doesn't sound feasible to purchase a $45 check valve if the uploader valve is to blame and not possible to obtain. Or, could a different uploader valve be used if it can be acquired and affixed to the pressure switch?

Are my previous symptoms a clue to which valve went bad? If the uploader valve is a basic standard part on compressors is there a place to purchase such a part?

Also, is the uploader tube and uploader valve a factory assembly or two individual parts?

Thanx for your site. It is a introduction to the basic workings of an air compressor.
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Many questions, Bruce. Let's see if I can answer some of them, and, thanks too for your kind comments about my site.

The unloader valve is supposed to be open (passing air) when the compressor is stopped. This opens a flow path from over the piston to atmosphere, and bleeds off any air that might be trapped, helping the start process when the compressor starts the next time.

If your tank check valve is dirty or failing and it does not shut tight, air bleeds out of the tank and then out the unloader valve.

So, first, dump all air with the compressor off, pull the check valve, and check and see if it is actually only allowing air in one direction. Sometimes it's just a bit of crud preventing the seals from closing. Make sure it works.

If the check valves works, then the other culprit will be your unloader valve.

If, after reinstalling the check valve and running the compressor to build pressure in the tank, you still have air bleeding out the unloader valve, then dump the air, remove the unloader valve, try to disassemble it, and see if there is debris in the seals that prevent it from closing.

No debris, time for a new one.

You can use any unloader valve that fits your air compressor and interfaces properly with the unloader valve operator on your pressure switch. Make sure that when the pressure switch trips to off, it depresses the pin to open the flow path. With the compressor running, the pin typically is fully extended and should not be depressed.

I suspect your only source for unloader valves will be on line. I don't know of any stores that actually carry spares.

Cheers,

Bill

Comments for Craftsman 106.175781 - unloader valve continuously leaking?

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Dec 10, 2012
Re. uploader valve continuously leaking
by: bruce

Bill,

I just took off the check valve and there was a small 1/4" screw on top of the check valve seal holding it ajar. The description of the screw as follows, approximately 1/4" in lenght, threads 6-32 or 8-32 with six small linear lines cut in the threads. I took the top plate off the head and seen the flapper valves. There are two loose screws out of four holding the flapper valves. One of those screws made it to the check valve. I am not sure where the fourth one is. It was not in the check valve or uploader tube. I am not sure if it made it to the tank. Or, inside one of the pistons to be mangled and then back to the tank. To replace the screws should be simple :) if that is all what the problem was. Do those screws need to be tightened to a certain ft. lbs.?
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Geez, I dunno, Bruce. Tighten them down, maybe put a little seal lock on them to keep them tight, and way you go.

The check valve isn't a high tech item. If the flaps close and seal, you're golden.

B.

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919.167783 pressure switch is leaking air

by John
(Pelham, AL)

After the unit runs the pressure switch is leaking air. It leaks for a minute or so and stops, but is getting worse. The motor wouldn't start up yesterday. It acted like it was stalled. After letting sit for an hour or so the motor kicked right on and the pressure switch didn't leak but a few seconds. The unit is a professional grade model 919.167783.
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G'day John.

When I first started reading I though, oh yeah, that's a leaky tank check valve. That may still be part of the problem. Check out the check valve page :-) for details.

Your symptoms about your compressor not starting easily suggest you may have an unloader valve problem as well. If the unloader valve doesn't work, air is trapped over the piston, and over-loads the motor on start up.

I cannot find any info on the 919.167783 Craftsman air compressor, so I suspect that it's old enough to require some service.

The two things I would replace would be the tank check valve and the unloader valve, it were my compressor.

Cheers,

Bill

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contacts for the pressure switch compressor model # 919.167320

I need a new set of contacts for the pressure switch. Can I replace just the contacts or do I need to buy a whole new switch?
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If you are trying to rebuild the switch to save money, I fear that you will be in vain.

What is the make of the switch on your compressor? Google that name to see if you can find parts. I expect that if you can, the parts, shipping, and aggro price to trying to rebuild the switch is easily offset by the typical $30 - $40 price for a new switch.

Bill

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hose going from the pressure switch to the check valve on 919.167620

by Corey Shaner
(Hughesville, Pa)

hose going from the pressure switch to the check valve

hose going from the pressure switch to the check valve

hose going from the pressure switch to the check valve
hose going from the pressure switch to the check valve

Model 919.167620 Craftsman air compressor. The hose going from the pressure switch to the check valve blew off. The end on the check valve is ok, but the end that goes to the swivel connector on the pressure switch blew off and the parts on that end went flying. There are 5 parts that I could fine that go on the end of that hose, but I don't know the order in which they go back on. The parts manual doesn't even show those parts. Also, I am guessing that since they blew off, they may not hold if I do put them back on the hose and make the connection. Picture 5037 shows the hose and the parts, the end that goes to the check valve is OK. Picture 5042 shows the swivel connector on the pressure switch.
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Thanks for the photos, Corey.

It looks like the tube in question is polyurethane, soft like, and it was connected to the fitting by a collet that "grabbed" the skin of the tube and held it in.

A couple of options.

Unscrew the fitting where it goes into the housing and replace it with another 90 degree swivel elbow designed to handle P.U. tube (an instant fitting type). That may not work as the tube itself may have hardened up to the point where it cannot be secured, or, shrunk over time so that the collet cannot hold it.

I'm a proponent of soft copper tubing for air lines on the compressor due to their resistance to heat, to water, and normal degradation. You can purchase soft copper tubing (1/4" tube would be my guess) at the plumbing store, along with the necessary fittings to replace those on your compressor with brass ones into which you can insert the tube, and have it secured by tightening a nut on the fitting. That's a tube and ferrule type of fitting, and they are standard.

Cheers,

Bill


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