No hydraulics on a Case 621

[tightgtp]

I have a Case 621 that lost pilot pressure for the lift. The steering works fine. I only have 25-0 psi of pilot pressure at idle. After troubleshooting I found the two check valves that connect the hoses from the steer pump and hyd. pump to the pressure reducing valve trashed, the ball and seat was wore out and the spring broken. I have new on order. Has any one else had this problem? Your help is very appreciated.

 

[Arabhacks]

Sudden?

Hello.

Is this a sudden failure? if so it may be indication of abuse.
If the bucket is overloaded check valves and the like get damaged pretty quick.

 

[tightgtp]

it was an intermittent problem the last two weeks and then it completely stopped. the customer is rough on equipment though.

 

[quackattak]

i had that same problem before, replacing the check valves fixed it.

 

[tightgtp]

i changed the check valves and you unit still did not work. i was checking hyd. pressure again and could not get any. i did finally get some pressure after dead heading the steering but that was it. i'm leaning towards a bad hydraulic pump. i did check the main relief but that was ok.

 

[quackattak]

those gear pumps are fairly durable, there is a coupler on the drive shaft of the pump, maybe worn out? If you drain the oil to remove the pump, you could take that round plate off the left side of the tank and see how the suction screen looks. We have 5 621's running around never had a pump just quit.

 

[tightgtp]

isn't the hyd. pump closest to the trans and the steer pump is piggybacked on that one? so if the coupler for the drive shaft is wore wouldn't the steering not work?

 

[quackattak]

I think so, I know it was that way on the old w-series. I'll look tomorrow. I have a new pump assembly on the shelf I'll look at. Still might be suction screen.

 

[tightgtp]

but wouldn't the steering be affected by a suction screen being plugged?

 

[quackattak]

just sayin you might as well look when you drain oil to pull pump, a bit of a long shot. The problem still points to the check valves, there purpose is to keep the boom and steering hyds separate. Its been awhile since I had trouble with on but I will study one for a few today. Is yours a 621 or 621b?

 

[tightgtp]

i have a straight 621. i did change the check valves .

 

[tightgtp]

today i got the new pump in. i can get the tilt to work a bit but no lift. i pulled the pressure reducing valve out and disassembled to make sure i didn't have any left over pieces from the check valves. everything checked out ok. i was looking at the parts diaghram and noticed there is a low pressure regeneration valve on the control valve i didn't know if this could be a problem or not. i'm getting about 100 psi of charge pressure at idle when deadheading the steering i get about 475. is this normal? i guess i'm also a little confused at how the steering comes into play with the pressure reducing valve. suction screen was clean

 

[alrman]

tightgtp,

621 loaders built prior to JAK 00202386 have a pressure regulating valve which recieves oil from steering pump & sends 80psi to remote control valves - does yours fall into this category?

 

[tightgtp]

my serial # is JAK 00027078. sounds like it does. but my pressure regulating valve recieves oil from the steer pump and hyd. pump. both lines go to a tee going into the valve.

 

[alrman]

this diagram shows exactly what you describe
you should have 550psi at the test point near accumulator while at main relief - (if you can get it )
I guess you've tried adjusting the regulator? with no response at gauge...?

 

[tightgtp]

i don't think the regulator is adjustable

 

[alrman]

just figured how to post this - may help
There is supposed to be a allen headed screw under cap (that's what my book says..?)
Re : pressure reducing valve - looks like regulator to me.

 

[tightgtp]

i'm not sure if you got this out of a service manual but in the accumulator test. what is the pressure reducer?

 

[tightgtp]

ok thanks i'll check that. i had it out today to clean the entire valve. i looks just like a cartridge type relief valve. i had no idea it was adjustable. its not a very big cap that covers the allen screw. i hope this is the problem. theres not much left in the system to check. thanks again.

 

[quackattak]

The only one I've had that problem with is a 621b, different set up than yours. We have 3 621s with your set up. looking at pic it almost has to be that valve or you have joystick problems.