GX CS4 'O' rings supplied with new compressor.

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Grey-Kiwi

Grey-Kiwi

Member
Feb 25, 2022
61
42
Richmond, New Zealand
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.
 
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1900colt said:
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.
Click to expand...
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
 
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The rubber diaphragm in my grease pot developed a split after a few hours of run time and piston pulled in alot of grease. Found on here somewhere easy way to check for over greasing, and blow of excess grease is to remove the check valve under burst disk and just let it run. Place a tissue or something over the hole and check for oily residue after about 30 minutes. If it's present just keep letting it run till excess is blowout. To a few hours, but mine had sucked in most of the gease pot.
100 hrs now, no issues and still deadheading 2 or 3 seconds of out the box.
 
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Nope, checked and cleaned the check valve a couple of times.
Mine has really worked OK, but even from new as it approached 3000psi the gauge slowed down a lot.
I thought at the time that I'd hate to be waiting for it to fill a cylinder to 4000psi.
So it's going OK I think. But if I buy another PCP requiring a higher fill pressure than 3000psi then the CS4 might become a pain.
No leaks. Done the soapy water, the dead head, etc and no problems. Fill my cylinder to 3000psi and let it sit attached to the pump for 1/2 an hour and the gauge doesn't move.
I'm just thinking ahead, and planning to (one day) strip the pump down and do new seals...just in case.
My main query was about the seal kit supplied and did GX short-change me for a few O rings.
 
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