[dannymarilyn]

Just rebuilt Gast compressor with the rebuild kit from Gast (about $241). Easy to do, but not for sure if needed. The biggest problem was the compressor outflow check valve allowing air to feed back into compressor. I installed a new pressure relief valve that is on the opposite head and it is no better than the original. During my test (test jig into a big portable tank, about 10" x 30"), I found some air still leaking around the cylinder heads. I called Gast and the tech person advised me that was basically normal to allow the air to leak off the heads for the next starting sequence. It was just very fine, very small bubbles around the head gasket.
The air line to the pressure switch was one of those $*%%^push in type air fittings. Now changed to DOT compression types (1/4") with NO leaks. Also, a weatherhead socket is handy to remove the brass fitting off the switch. Tight fit and the screws would not release the bracket. I bought mine at Sunex, on Amazon, of course. I added a air/water separator to the compressor output hose (3/8"). I didn't have the space anywhere else to install a slightly larger compressor. If anyone has another Gast cpompressor laying around, I'd like to buy one for a spare. This one only lasted about 34 years.

[whited44]

Just rebuilt Gast compressor with the rebuild kit from Gast (about $241).  Easy to do, but not for sure if needed.  The biggest problem was the compressor outflow check valve allowing air to feed back into compressor.  I installed a new pressure relief valve that is on the opposite head and it is no better than the original.  During my test (test jig into a big portable tank, about 10" x 30"), I found some air still leaking around the cylinder heads.  I called Gast and the tech person advised me that was basically normal to allow the air to leak off the heads for the next starting sequence.  It was just very fine, very small bubbles around the head gasket. 
The air line to the pressure switch was one of those $*%%^push in type air fittings.  Now changed to DOT compression types (1/4") with NO leaks. Also, a weatherhead socket is handy to remove the brass fitting off the switch.  Tight fit and the screws would not release the bracket. I bought mine at Sunex, on Amazon, of course. I added a air/water separator to the compressor output hose (3/8").  I didn't have the space anywhere else to install a slightly larger compressor.  If anyone has another Gast cpompressor laying around, I'd like to buy one for a spare. This one only lasted about 34 years.

Where was the outflow check valve located??  What does it look like?.  I may have the same problem

[dannymarilyn]

Dear Dennis, The outflow check valve was the first fitting connected to the nipple on the compressor cylinder head. The outflow went through the check valve into the compression fitting which goes into the belly of the coach on ours (#277). Our compressor sitting on a shelf just above the generator cooling blower in right front compartment. When I reinstalled the compressor, I trimmed the insulation off the wall separating the compartment from the generator box. The insulation was hindering cooling air flow around the inside cylinder head on the compressor. I'd suggest disconnecting the outflow hose and remove the fittings connected to the compressor. Don't try very hard to remove the brass fitting screwed into the head. The heads are aluminum and the brass corrodes into the head and won't come out. On ours, the fitting out of the head is a 90°, then the inline check valve, then connecting to the compression fitting. I re-plumbed everything with DOT
compression fittings - they don't leak! On ours, the other head mounts the pressure relief valve in that head. The compressed air travels under the heads to merge. As long as you are removing brass to brass fittings, no problems. When you remove the valve, just look through it.
You'll see the one-way valve. You can suck air through it one way and nothing in the other way! I bought one in a hurry from Fleet Pride. I have two spares from E-bay for about $25 apiece. It should be 1/4" NPT sized. I used 1/4" brass fitting from local hardware store for nipples and connectors for my road kit. Let me know if you wish pictures. deg

[whited44]

Mine must have a check valve further down the line. When I remove the hose off the compressor air does not come blasting out