Hello All, Our city has a 710a Champion grader 1991. Recently, the steering has begun to act up. When the grader starts up cold, the steering cylinders react to the steering wheel with only a little lag in reaction. As the system warms up, the reaction gets less and less until there the steering wheel can be turned continuously in either direction with little to no response at all. At the advise of a local tech, the steering valve was replaced. This did not resolve the issue. I'm curious if any of you would have a recommendation on the next best place to start? In my opinion, these are some possible culprits. 1.Hydraulic pump. (However, the brakes and clutch seem to work fine--am I correct in seeing from the schematic that the pump supplies flow to steering, clutch and brakes). 2. Seals in the steering cylinders. I feel like this is another area that as the oil warms up would get worse. However, the cylinders also appear to be hooked in Master/slave set up. I think it would have to be both cylinder seals bad for it to react that way? 3. I'm curious about the cushion valve near the cylinders. If I understand it correctly, if the cartridge in this is bad it could allow oil to completely bypass the steering cylinders. Perhaps simply pulling the cartridge out would give us a clue. I'd appreciate any ideas for testing/troubleshooting you could give. Thanks! John S.
I'm not sure the cushion valve is for the steering but maybe. You might have an issue with the orbitrol/steering valve the steering wheel attaches to. May need new seals or rebuilding. How does it steer when you pick the front wheels up? Might be good to do some pressure checks.
Thanks Dave. The orbital valve was actually replaced but did not resolve the issue. Lifting the front up is a good idea. Also, the schematic in the service training manual states the the cushioning valve will allow the steering hoses to interconnect if the pressure on either side is greater than 1200 psi. I'm suspicious that if something is wrong in that valve the oil could completely bypass the steering cylinders.
I'm not sure how cushion valves work but maybe if something is stuck they redirect the oil. Maybe you could bypass the cushion valve just to try the steering without it. I've got a lock/cushion valve on a ripper. When I went out to clear my driveway the ripper was down. Odd because it always stayed up and when I went back out a few weeks later it was still up. I wondered if maybe I lowered it just slightly so it wasn't tight against the ripper frame? Thinking maybe it depends on the last way the valve was activated. If I lifted the ripper then it doesn't creep. If I last lowered it slightly it creeps.
Continuous spinning of the orbitrol when hot sounds like steering cylinders to me. Easy way to check steering cylinder is hold it on the lock (if you can) and feel if the cylinders get hot. Or crack the opposite hyd line.
Thanks Guys--gonna try a couple of those things this weekend and will report back.
Hey John, It sounds like you’ve already done some solid troubleshooting, and your suspicion about the cushion valve bypassing oil is definitely worth checking. Since the orbitrol has already been replaced, I’d say your next best steps are: 1️⃣ Steering Cylinders: Continuous spinning of the wheel with no response when hot often points to internal leakage in the cylinders. A quick way to check is to hold the steering at full lock and feel if the cylinders heat up—leaking seals generate heat. You can also crack the opposite hydraulic line and see if oil is bypassing internally. 2️⃣ Cushion Valve: If this valve is malfunctioning, it could be allowing oil to bypass the cylinders entirely. You might try temporarily bypassing it to see if that changes anything. 3️⃣ Hydraulic Pump: While the brakes and clutch working fine suggest the pump is delivering some pressure, steering systems are more sensitive to flow loss. A pressure test could confirm if the pump is struggling under load. I’ve written in-depth about hydraulic steering systems, including troubleshooting issues like this. You might find this helpful: Hydraulic Steering Systems . Let me know how it goes—I’d love to hear what you find!
That crap as “classic” as replacing main pumps on excavator because it boggs the engine down. Diagnostic? No - haven’t heard of it.