has leaking air

by Stan
(Hardeeville SC.)

I hve a CGBN125A-3 Portor Cable that has developed a leak and removed the cover to inspect which makes it impossible to run the unit to test for leaks.

Hoses look good but did notice the metal tube attached to the cylinder head has a lot of play.

Could that be the problem?

Bill says...

Could be, Stan, but let's probe further.

Tell me about the leak. Lots of air bleeding down the tank so that the compressor has to restart often, or a slow leak that empties the tank over a period of time, even when it's shut off?

I'm not sure why the cover should interfere with the running of the compressor. Is there some sort of switch that you've had to disconnect to get the shroud off?

Comment here if you would so I can follow our discussion.



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Feb 22, 2017
loose air tube from head
by: Anonymous

loose tube from piston head is the point of my leak. I see nothing addressing this problem when it has been stated. I would like not to go in blind when I remove the head from my porter cable 150psi pancake compressor.

(Please start a new thread under Porter Cable compressors and add a photo of where the problem is. - Moderator)

Dec 06, 2015
Have the same problem
by: Raul

I have the same problem and the leak is from the top of the cylinder head

Sep 29, 2011
Leaking air
by: Anonymous

Thanks Bill,

It has to be the problem { metal line from head to tank too loose}. The problem I see is that you can buy the line not attached and I have no Idea how it tightens to the head tightly?

Is there a way to contact Porter Cable to get an answer?



Sep 28, 2011
Leaking air
by: Stan

I will try using another compressor to find the leak.

I would still like to find out if the metal line needs to be tightly attached to the head. It may be too expensive to repair?

thanks for your patience



If you mean the metal line from the top of the compressor pump down to the tank, yes, it should be attached firmly. If it is not, air will leak out while the compressor is pumping. Air should not leak out of there once the compressor stops.

Sep 25, 2011
Leaking air
by: Stan


In order to start the comp. I have to reinstall the cover and then before I can remove the cover to find the leak is so fast I do not have time to remove the cover in order to find the leak.

Do you think I can remove the pressue inlet hose and put air into it to find the leak? Do you know how the metal pressure outlet tube seals against the piston head?

Thanks again



Stan, reassemble and start the compressor. Let the pressure in the tank get to cut out level, or as close to it as it will go. Shut it off. Inspect and listen to find the leak. Particularly check the unloader valve to see if it is blowing air with the compressor off. Let me know if this is the source of the leak.

"Do you know how the metal pressure outlet tube seals against the piston head?" Not quite sure what you mean here. Do you mean what type of fitting? If so, start another post and upload a photo and we'll have a look.

Sep 22, 2011
"has air leaking"
by: Stan


The unit was pumped up to 100lbs. and I could hear it leaking and when it was refilled then the pressure would not build and I could hear it leaking as fast as it was being filled.

As far as the cover, the on-off switch is mounted to the inside of the cover and if I remount the cover I just can't see inside the cover to find the leak. I guess I could try mounting the comp. in a vice and try wiring it direct but I am a little scared to try that.

Any other suggestions to finding the leak?


Is the unloader valve beside the pressure switch. Is the air leaking from there? If so, your tank check valve is pooched. You need to get some air into the tank to find the leak.

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C2005 bleeds air through cylinder head

by mike yozell
(Emmaus pa)

Compressor comes to full pressure, shuts off correctly then leaks air from a pin hole in cylinder head near where reed valves are located. Is the pinhole supposed to be there? what is supposed to keep air from bleeding out there?
First off Mike, once the air compressor shuts off, there is no way compressed air is supposed to bleed out anywhere. The tank check valve's purpose is to keep the compressed air in the tank until you open an downstream air line to an air tool to use the air.

So, if air is bleeding out anywhere, then I would surmise that the tank check valve is fouled or failed.

Next, I cannot locate a photo of this compressor to try and see, but here is what I surmise. Assuming that the pin hole is not a structural failure (and I don't know that) then it may be there simply to bleed air off the cylinder head, may bleed air all the time when the compressor is running but since it's a small hole, more air goes into the tank when the compressor is running than out the hole. Then, when the compressor stops, the left over-the-piston air bleeds out the hole, and the compressed air in the tank stays there unless you use it, and unless the tank check valve is wonky.

I've never heard of this permanent bleed hole in a compressor pump head before... so this is just surmise on my part.

Anyone else?


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Nov 10, 2013
C2005 bleeds air through cylinder head
by: mike yozell

Thanks Bill, after I posted I did pull the check valve. It was corroded. Ordered a new one and it works fine. Inexpensive compressor that has been one tough worker.
Glad to hear that I was close.



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Porter Cable c7510 60 gallon hissing air in line between cylinders

by Greg
(Seattle, WA)

Ok, you said there were no dumb questions, so here goes.

I have a Porter Cable 60 gallon compressor.

There is a copper line connecting the 2 cylinders. In the fitting into one of the cylinders there is a small nickel diameter valve - it leaks a short squirt of air with every stroke of the cylinder. It has a small needle that pops out of it. It leaks air from the minute the compressor is activated (even with zero pressure at the start) and continues until approximately 100 psi, at which point it stops emitting air, it seals up, and the compressor continues to run until it reachs 120-126 psi and the compressor stops.

I don't think it takes a particularly long time to come up to pressure and the compressor seems to work fine, but this bugs me. Is this the way this compressor is supposed to work? I cannot find anything about this valve in the parts schematics that I find online. If you are standing in front of the compressor the valve that I am talking about is on the cylinder to the right, ie the cylinder furthest away from the motor. Anybody have any ideas?

Thanks, Greg

Bill says...

Greg, I'll take a stab at it, and invite anyone else with this Porter Cable c7510 air compressor to join in.

What I think you are seeing / hearing is the PRV in the line between cylinders. That suggests to me that you are getting back pressure in the line between the two cylinders, causing the PRV to pop open intermittently, and that suggests to me that you may have an intake valve issue on the second cylinder.

Just my .02 cents worth. Anyone else?



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Jul 11, 2012
Porter Cable PRV
by: Anonymous

check the parts diagram for a description of the copper tube - it should say something like "cooling air tube", if I'm recalling it correctly. I own the same model (PC C7510) and the relief valve operates (is open and hissing) from 0-80 psi. If I understand it correctly, the tube provides cooling airflow inside the heads during the run-up from 0-80.

Mar 08, 2012
valve worked
by: Greg


A quick follow-up -

The valve I mentioned and ordered did the trick. No more hissing issues thank goodness. It looks like it was a good craigslist buy after all!



Good stuff.


Feb 10, 2012
more on the valve in question
by: Anonymous

Hi Bill,
I can't believe your quick responses, thanks.

I find the part on this website parts schematic, on the second picture.


The part is #153 D28198
Valve Flow .375NPT 8

I can't find any information about this valve anywhere on the internet. But, like we say, it is cheap and I'm ordering one right now. I'll report back after I try it out.

Regards, Greg
10-4. Thanks for keeping us updated.


Feb 09, 2012
"valve flow"
by: Anonymous

Hey Bill,
The parts catalog shows the valve I ask about as part d28198 "valve flow". Is this the unloader valve? Could it being bad cause my symptoms? I hope so, that would be a cheap fix.
Thanks Bill,

The schematic I found on line does not show the fitting you refer to either. What I referred to as an in-line PRV may be this unloader valve, and if it's a cheap fix, why not give it a go? At worst, you'll have a spare.

Feb 08, 2012
by: Greg

Thanks for the response to my question. I'll check it out, at least it's a lead!

Regards, Greg

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model c2006 type 2 fills and shuts off. leaking air

by Roger
(Bellevue, WA)

Porter Cable c2006  compressor head

Porter Cable c2006 compressor head

MY c2006 type 2 compressor will fill and shut off automatically. However, it is leaking air out of the cylinder head. I can feel air coming out of the hole in the cylinder head that is below the boomerang shaped 'v' om the cylinder head.


Not sure if i need a new head, valve plate or gaskets or all three.

Any advice?

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Jan 28, 2017
hole in top of head
by: Anonymous

The hole in the top of head is normal like others have said, it is to unload the cylinder so the compressor does not have to start loaded. If air is leaking out that hole look at the check valve that holds in the air pressure in the tank. I agree with what some others have said this is your problem.

Nov 07, 2015
Head is fine; replace check valve
by: Dion

I have the same compressor with the same problem. If the hissing is coming from inside the plastic case where the compressor motor is, then it is probably coming from the pressure relief "hole" in the top of the compressor head. This is a smooth pencil-point-shaped hole in the top center of the head that relieves the pressure inside the cylinder when the compressor is not running, which enables easier starts without overloading the motor.

Before you panic, this is NOT a problem. That hole is SUPPOSED to be there, and is the source of the hissing you hear for a second or two each time the compressor motor shuts off when the compressor is operating normally.

The problem is the one-way check valve where the rubber hose from the compressor motor meets the tank (part number 8 on the parts diagram). If that one-way valve fails, pressurized air that is supposed to remain in the tank flows back up through the hose and exits the pressure relief hole in the compressor head (path of least resistance). The cure is to replace the one-way valve (less than $20 from most sources).

In the meantime, you can continue to use the compressor. The compressor fills the tank faster than the pressure relief in the head releases air. The downside is it will hiss constantly, it will bleed down when not being used, and the compressor will run much more often, which will reduce its service life.

Sep 05, 2015
compressor hole in the head
by: Bruce

well to my surprise i stuck that green piece of putty back in the hole and fired it up and it works like a charm,I assume it got to hot and blew out but with out it the compressor won't build pressure so if anyone is having this same problem look for the piece of green putty when you take it apart

Sep 03, 2015
hole in the top of the head
by: Bruce

Not sure what that hole is but mine is leaking out of it to.I took the housing off and a little piece of green putty fell out and I'm assuming it came out of that hole,maybe it's a safety thing

Jul 12, 2014
Fixed mine
by: Anonymous

Had the same problem, it was the check valve at the tank had failed, the pressure was leaking back through the hose and into the head then out that hole. I believe that hole is for pressure release so the compressor doesn't have to start under load. If you remove the check valve, (it will probably be contaminated with rust) and test it by blowing through from the tank side there should be no air passes through it.
Great answer, thanks.


Feb 10, 2014
by: Doug in s.d.ca

If you can't tell from the parts breakdown, you'd prolly want to order at least the gaskets, and maybe the valves.

You should be able to tell if you need the head once you get it off.

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