Hydraulic pressure relief valve stopped holding

We are installing a "PTO wet kit" on our truck.
The kit, that I bought at a truck parts store, consists of a Muncie
PTO, 13 GPM gear pump, and a pressure relief valve with a cartridge
similar to Sun RPGC-LAN. I say "similar to" because the actual model
is a fixed pressure RPGC-L2500N, but it is hard to find anything in
google about that model number. RPGC-LAN is a number that is easier to
I had a tank that I put to use.
Anyway, we did a first test of the system, with the output and return
hoses connected directly to each other. No problem.
Then we left the hoses disconnected, so that there was no circuit, and
proceeded to run the pump to test the relief valve at full pressure
and to warm up the oil quicker.
At first everything was great, pressure held at 2500 PSI, everything
was flowing. After a while, though, something happened and pressure
dropped to 500 psi, then more.
I started looking. The pump pumps with good flow, I know this because
I pumped some oil into a bucket.
Took out the pressure relief cartridge. I found out, to my surprise,
that it is very easy to puch the piston in with a plastic pen. If it
is a 2500 PSI valve, it should have taken a force of several hundred
pounds. Instead I can easily do it by hand.
The picture is here:
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I do not really understand what could have happened and why this valve
could fail and become so easy to open.
Would anyone have any idea? What could it be?
Reply to
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The spring inside it broke
Reply to
Karl Townsend
That is what I think too -- but I wonder, how could that happen?
Reply to
"Ignoramus21464" wrote in message news: snipped-for-privacy@giganews.com...
My Husqvarna chain saw eats expensive made-in-Germany clutch and recoil starter springs.
Reply to
Jim Wilkins
Material or procedural defect in the manufacture of the spring.
Reply to
Larry Jaques
Karl Townsend fired this volley in news: snipped-for-privacy@4ax.com:
That's the most likely scenario. How many decades has it been running at near top pressure in a "full-singing chatter mode?"
When they squawk (and of course they inevitably do), they're wearing out ball, seat, and spring.
Reply to
Lloyd E. Sponenburgh

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