Hydraulic control valve for Case 770

I need to replace or rebuild the hydraulic control valve on my Case 770. Does anyone have any advice on how to rebuild one or know of someone who can rebuild one or possibly sells rebuilt valves.
Thanks

If you are referring to the control valve below the fuel tank most parts are available from Case.

Depending on what is wrong with yours some repairs like replacing the thermal valves can be done without removing the whole valve from the tractor.

Is this the control you are talking about and if so what is wrong with yours?

(quoted from post at 07:20:07 06/16/20) If you are referring to the control valve below the fuel tank most parts are available from Case.

Depending on what is wrong with yours some repairs like replacing the thermal valves can be done without removing the whole valve from the tractor.

Is this the control you are talking about and if so what is wrong with yours?

Click to expand...

Yes, I am referring to the control valve under the fuel tank. The tractor has a scoop on it and it is getting harder and harder to pick up the big round bales with the scoop. The power shift works find, no hesitation, so I figure the hydraulic pump is good. I suspect the hydraulic valve needs to have some o-rings replaced or something. Trying to find someone who can offer some advice. None of the local repair shops seem to want to look at it. The problem seems worse when clutch is depressed it that helps.

Your first step is to diagnose what or where the problem is.

-Could be anything from;

Low fluid
Plugged filters
Cylinder leaking internally
Mechanical binding
Water logged bales that weigh more than you think
Weak hydraulic pump
Thermal valves in control valve
Relief/bypass valve setting....

I would start with a pressure gauge (0-5000 psi) put a male coupler on it so you can plug it in to each remote coupler and record the pressure, this will give you a basic idea of where to start looking.

Lacking tools or gauges you could start with marking where your loader couplers are currently attached then try swapping your hydraulic circuits around, unplug the top 2 hoses and reconnect them left to right your control handle will now operate opposite of before.

Next try swapping the top 2 with the bottom 2, this will change which handle controls lift and tilt but again this is just a place to start for test purposes.

If either of the above shows big improvement in lifting ability it would suggest that the pump is functioning properly but the control valve may have bad thermals or a coupler may be restricted.

Another simple test would be to raise the loader shut off tractor, disconnect couplers, measure and record height of bucket then let it sit overnight.
If the bucket drops a considerable amount overnight and there are no external leaks then this is a pretty good indication that one or more cylinders are leaking internally.

I believe we can eliminate the obvious problems such as low oil. binding, or excessive weight.

I put a coupler on a pressure gauge and tested all four remote fittings and got around 2000 psi with the engine at full throttle. I think that would rule any major problems with the hydraulic pump.

You mentioned the thermal relief valve. I have an I&T shop service manual with an exploded view of the hydraulic remote valve and it shows a thermal relief valve. Is that a replaceable or repairable piece?

Is there any easy way to check the relief valve, other than the method described in the I & T book?

Is there any other things I could test that don't require alot of specialized equipment?

Thanks for you help.

What kind of pressure are you getting at an idle and half throttle?

When you attach your gauge and get the reading is it holding this pressure or is it fading fast when you release the control?

Pressure is only part of the equation, flow is just as important.

Have any lines or fittings been replaced with ones smaller than original?

Steel lines on loader frame, any crushed or flattened areas?

When were the hydraulic filters last changed?

Have you tested for internal cylinder leakage; loader up, couplers disconnected, let sit overnight?

With a bale on it is it lazy lifting and tilting or does the tilt function seem to still have adequate power?

Anything but a complete evaluation of the system with a flow meter bringing the system oil to operating temperature to evaluate the system performance is a bit futile in my opinion. The pump can be tested directly with the system out of circuit to give a very accurate look at its capability. I consider a pump marginal if it is giving up much more than 20% of its flow cold to hot. Flow testing will pinpoint problems that take hours trying to narrow down by trial and error, I realize that all may not have that equipment at hand but all Case dealers are required by their contract to be able to test.

That being said, if your system is stronger hot than cold you should be suspicious of the pump as your relief pressure at wide open throttle seems to be on target.

Sorry, re reading I saw my error, if your system is stronger cold than hot pump could be suspect!!

BF, Re reading your original post the last sentence hit me, If the power shift is influencing the speed or power of the hydraulic circuit it could be that a leaky clutch is robbing the hydraulic of needed flow, the tractors flo divider satisfies the power shift first then the remainder of the oil gpm flow goes to the main hydraulics, transmission pressure is only 210 lbs so pump pressure is not the issue, the lack of oil flow to the hydraulics caused by a leak in the power shift shows up as slow or no hydraulics. if the loader speed varies depending which power shift speed you are in that points to a leak inside. It is interesting that clutch down seems to make it worse as that is C2 released not receiving any flow. do a little further testing as I described and get back, these tractors are a bit more complex than a simple open center hydraulic system. As before, a flow test is able to tell clutch leakage down to 1/2 GPM, that would be the ideal.