555D Backhoe Hydraulics---stumped at present

LeakyBoot · Jul 17, 2015

While replacing engine had pump off. Was working fine up until it was removed and replaced. Caution was taken to keep dirt out of the open lines. After getting it all back together and topping off the fluid it does not have much pressure or volume. Everything works slow and will not even move much at idle speed. My idea was something was stuck in the main relief valve. Have removed and seen nothing. No change in how it operates. Have drained and checked the suction lines between pump and tank. I don't have a test gauge setup but I would guess the entire system can't make much over 500 psi. I assume the pump is a gear pump with no built in relief valve? Any help on this little puzzle? Thanks, LB

RodinNS · Jul 18, 2015

I'm not really familiar with that system specifically... but I guess what I would suggest at this point is that if you don't see any suction leaks and the relief valve is not opening... then I'd probably want to get a good set of gauges and flow meter and start testing. you'd have to open the supply line from the pump and tap into that and see what flow it makes at rated pressure... or if it makes rated pressure. Then decide to go forward or backwards from there. The only other cheap suggestion I can make is that you find the suction strainer/filter(s) on the machine and check and clean them. A lack of supply to the pump could cause the difficulties you have...

Rod

Bern · Jul 18, 2015

I'm going completely off of my memory here, but I'm all but positive that the main system relief valve is in the loader control valve stack. If this is the case, I'd flow and pressure test the pump directly, either at the pump or the loader valve, whichever is the most convenient. Most shops would use a pressure-flow load tester to get this done. If you don't want to purchase one, a poor man's substitute would involve a high pressure hose, a needle valve, and a 5-gallon bucket. Less than $100 would build you one.

I would strongly suggest purchasing or else borrowing a repair manual for your machine and studying up on the system. I'm sorry to report that I've thrown all of my training materials for that machine out.

555D Backhoe Hydraulics---stumped at present

LeakyBoot

Member

RodinNS

Well-known Member

Bern

Well-known Member

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