I have a CGBN125A-3 Porter 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, says Stan from Hardeeville S.C.

Well Stan, it’s a bit hard to tell from here. Is air leaking from that fitting? If not, then no, probably not the problem. Makes me wonder how you know that the compressor has a leak?

I’ve tried to find an image of the Porter Cable CGBN125A-3 compressor but have been unable to do so. Perhaps you could upload a photo?

On another issue, Mike from Emmaus PA writes in about his C2005 bleeding air through cylinder head.

The 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?

Porter Cable C2005 air compressor
Porter Cable C2005 air compressor

Mike, once the air compressor shuts off, there is no way compressed air is supposed to bleed out anywhere for more than a second or two.

The tank check valve is supposed 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.

I cannot locate a photo of this compressor to confirm it, 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.

Greg from Seattle WA adds a question about his Porter Cable c7510 60 gallon compressor that is hissing air in line between cylinders.

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 reaches 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

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?