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Rolair K30
- Dave G.
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12 years 1 week ago #50
by Dave G.
Rolair K30 was created by Dave G.
Back ground: I have a new to me used SnapOn Big Red series upright compressor with a K30 pump on it.
When I started looking it over I found a head gasket leaking just by turning by hand. Because of it I did a valve / gasket kit before getting it hooked up. The cly looked good so I did not see the need to replace rings or pistons. Head & plates measured flat. I was also told the pump was new about 2 years ago but taking off line for a year before I bought it. It did look like it was run hard for that year with the dirt on the pump assy. And air filter. I was also told the PSI start/stop switch was bad (don’t know why they said that) so new one was bought & replaced with the head kit from you guys.
Now the issue: After the pump runs, only had it up to 100 psi, and shuts down I have air coming out the crank case breather (this was replaced too and fresh oil) but not out the PSI switch. It is not a lot of air but will drain down the tank if left and know it is not right. I am thinking it is the check valve but being I have no air out the switch like your video said I am at a loss. I have not removed the pump discharge pipe yet to see if air is from it but I cannot see anywhere else the air could be coming from.
So check valve or not to check valve?
Thank you for any help you can give.
Dave G.
When I started looking it over I found a head gasket leaking just by turning by hand. Because of it I did a valve / gasket kit before getting it hooked up. The cly looked good so I did not see the need to replace rings or pistons. Head & plates measured flat. I was also told the pump was new about 2 years ago but taking off line for a year before I bought it. It did look like it was run hard for that year with the dirt on the pump assy. And air filter. I was also told the PSI start/stop switch was bad (don’t know why they said that) so new one was bought & replaced with the head kit from you guys.
Now the issue: After the pump runs, only had it up to 100 psi, and shuts down I have air coming out the crank case breather (this was replaced too and fresh oil) but not out the PSI switch. It is not a lot of air but will drain down the tank if left and know it is not right. I am thinking it is the check valve but being I have no air out the switch like your video said I am at a loss. I have not removed the pump discharge pipe yet to see if air is from it but I cannot see anywhere else the air could be coming from.
So check valve or not to check valve?
Thank you for any help you can give.
Dave G.
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12 years 1 week ago #53
by MTR-Admin
Replied by MTR-Admin on topic Rolair K30
Thanks Dave,
Well you're on the right track it sounds like. I alwasy recommend doing a check valve test first as this is THE single most common problem with any air compressor. I would get some air in the tank (100psi is sufficient) and after it shuts off, begin to take off the main Transfer Tube from the pump. If you get ANY backpressure at all from the tank then the Check Valve is defective and either needs to be cleaned out or replaced. Many times there is just debris inside (possibly gasket material) that will hang it up so it can't seal after the unit shuts off.
This is really the ONLY reason the unit would bleed empty if left off, completely. The check valve is the only one-way valve at the tank so if it doesn't seal then air will back-feed through the pump head, cylinders and out of your oil breather assembly.
It may not leak out of the pressure switch/unloader valve, possibly, because the unloader valve could be clogged or the o-ring/spring inside of the Unloader Valve is keeping air from leaking out of it. USUALLY this unloader valve leaks if the check valve is defective, but not always.
Hopefully this helps, and please feel free to post your findings on this forum when you test the check valve!
- MTR
Well you're on the right track it sounds like. I alwasy recommend doing a check valve test first as this is THE single most common problem with any air compressor. I would get some air in the tank (100psi is sufficient) and after it shuts off, begin to take off the main Transfer Tube from the pump. If you get ANY backpressure at all from the tank then the Check Valve is defective and either needs to be cleaned out or replaced. Many times there is just debris inside (possibly gasket material) that will hang it up so it can't seal after the unit shuts off.
This is really the ONLY reason the unit would bleed empty if left off, completely. The check valve is the only one-way valve at the tank so if it doesn't seal then air will back-feed through the pump head, cylinders and out of your oil breather assembly.
It may not leak out of the pressure switch/unloader valve, possibly, because the unloader valve could be clogged or the o-ring/spring inside of the Unloader Valve is keeping air from leaking out of it. USUALLY this unloader valve leaks if the check valve is defective, but not always.
Hopefully this helps, and please feel free to post your findings on this forum when you test the check valve!
- MTR
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12 years 5 days ago #60
by Dave G.
Replied by Dave G. on topic Rolair K30
Thank you for the reply.
I did some looking and testing (up to 175#) and the check valve is leaking (air was now coming out the new pressure switch too) so went and pulled it to get size. In doing so I found the check disc flopping around and some times would go sideways like a guide was broken?
So a new one has been ordered and when I get it installed I will give an update but I am sure this will fix the air coming out the pump breather.
Dave G.
I did some looking and testing (up to 175#) and the check valve is leaking (air was now coming out the new pressure switch too) so went and pulled it to get size. In doing so I found the check disc flopping around and some times would go sideways like a guide was broken?
So a new one has been ordered and when I get it installed I will give an update but I am sure this will fix the air coming out the pump breather.
Dave G.
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11 years 11 months ago #92
by Dave G.
Replied by Dave G. on topic Rolair K30
Up Date: Check valve fixed the air coming out the breather.
I also think the bad check caused the motor controller contacts to weld closed when it tried to start with pressure on the pump. This then caused the unit to never turn off.
Could be why the seller said may need new cut off switch and motor capacitors the cause was the bad check valve.
Thanks for all your help.
Dave G.
I also think the bad check caused the motor controller contacts to weld closed when it tried to start with pressure on the pump. This then caused the unit to never turn off.
Could be why the seller said may need new cut off switch and motor capacitors the cause was the bad check valve.
Thanks for all your help.
Dave G.
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11 years 11 months ago - 11 years 11 months ago #96
by MTR-Admin
Replied by MTR-Admin on topic Rolair K30
Excellent, glad to hear it 
The Check Valve is the most common problem by far and can cause all kinds of issues with compressors. Thanks again for posting your findings!
- MTR
The Check Valve is the most common problem by far and can cause all kinds of issues with compressors. Thanks again for posting your findings!
- MTR
Last edit: 11 years 11 months ago by MTR-Admin.
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