GX CS4 'O' rings supplied with new compressor.

Last year I bought a new CS4i compressor.
Only 3 hours on it, but it does slow up a lot when getting to 200 bar (~3000psi).
Thought I might give it a freshen up with the O ring set supplied with the compressor.
But...are there 'enough' supplied to do the job.
In one photo below is the complete set I received.
The other photo I shamelessly stole from another forum, and it shows a CS4 piston assembly...which has a lot more O rings fitted to it.
The GX site shows this...

GX-CS4-kit.jpg


I have this...

IMG20250606115610.jpg


This shows way more O rings, and that top O ring seems to have a fibre ring on each side of it, while the kit only supplies one...

O-Rings.jpg


Do I need more of that large fibre ring (at top of last photo)?
Do I need more O rings?
Where do those 2 little (the smaller ones) tapered springs fit (or will I discover that when I strip it down)?
Thanks.
 
It's odd that you are having issues at 3 hours. There are people on this forum that have 70 hours on them. I personally have 15 on a CS4 and 10 on a E5K2.

If you haven't torn it down try cleaning the check valves, it's easy.
I would also replace the green orings in the female foster fittings. All of my green ones went to "ship" in a hurry.
 
Last edited:
With only 3hrs, you probably have a leak.
You won't need all those seals for rebuild. If you did it would be catastrophic damage to have occurred.

If it doesn't leak down, is may be over greased.
I agree. Too much grease may be the culprit. This is a long shot but the problem might be a failing power supply or circuit board. A friend recently bought a CS4-i and had similar problems. He then ran the compressor on DC and it worked perfectly. GX promptly provided both a replacement power supply and circuit board under warranty.

JackHughs