Coy Lancaster
Senior Member
Have you tried adjusting the relief valve?
Me thinks you have problem with O rings on spools.I had a very similar problem with heaps of pressure variation with readings from 600- 1800 PSI yet the pump was pushing 3200 PSI. To fix I replaced every 0 ring and backup ring on the control bank. It's worked perfect since[/QUOT
Me thinks you have problem with O rings on spools.I had a very similar problem with heaps of pressure variation with readings from 600- 1800 PSI yet the pump was pushing 3200 PSI. To fix I replaced every 0 ring and backup ring on the control bank. It's worked perfect since
Have you tried adjusting the relief valve?
If you get 3,000 PSI for a full second, then I wouldn't turn up the relief valve, you might get more trouble. That sounds like it's sticking, or operating slow. I'd replace the relief valve, or take the old one apart some more to see if anything is bent, broken, or gummed up with garbage. Nothing to lose if your alternative is to buy a new one anyway. Just mark the position of the nut and put it back the same way on assembly.
Your next step would be a flow test on the pump, or replace it instead of testing.
Doug, I was a bit hesitant at the start as it was a job i'd never done before but I had no other option. 2 main things are to have a very clean work space and a good memory. ;-)
Thanks.Adjusting pressure is easily done by loosening the jam nut and turn allien screw in until pressure is correct.
You're welcomeThanks.
That pressure dropping is funny. With the engine cold, try the backhoe bucket curled for ten seconds and shut off the engine with the bucket curl held still, then jump off and take the temps of the hydraulic pump, loader valve, and backhoe valve. That might show you the smoking gun, hopefully not literally.
The pressure reacting differently makes me think the loader valve is leaking worse, but I don't know how the "power beyond" is set up to make the loader and backhoe valves work together. That is the key at this point. Unless the pump is hot and the valves are both stone cold with that test, then it's the pump, but how do you explain the pressure difference?
Without doing a flow pressure test directly off the pump, we're guessing.
The best way to find out is have a tech come out and preform a flowmeter test. This will take out all guess work cause all we'er doing here is poking a finger at problem.
Yes, it is a gear pump. So, if I remove the pipe coming from the outlet side of the pump at the inlet of the loader valve and cap it off, then I take the pressure reading at the test port?Is the pump a gear type? If so, there's a simple way to confirm if it's any good. Dead head the pump outlet and attach a high range pressure gauge. Very briefly crank the engine (disable it from starting). If the pump is good it will immediately peg the gauge.
This doesn't apply if it's a piston pump.
View attachment 180425 Wait until you install the new relief valve you have coming. You already said there was difference after you reinstalled it.
When you have it out, crank the engine a couple of revolutions so anything lodged in the passage-way can be flushed out. Have you changed the hydraulic oil filter and inspected the pressure relief valve ? It is in the hydraulic tank.
I would advise you to do that while waiting for the new relief valve.