Sudden loss of tilt on our 1970 Clark C70 7k lbs forklift. Eveything was working properly, fluids all at proper levels, then next morning NO TILT. Lift is fine. In researching our factory build manifest, two valves are listed. My immediate thought was that the control spool valve might have failed. But the tilt and lift spool valves are adjacent and part of the valve body casting, and lift funtions normally. Nothing visually evident when inspected. But the other of two valves listed in the build manifest is "Valve, Tilt Lock" (p/n 134371). Though adequately competent with hydraulics, I had no previous experience with the tilt lock valve, though I understand its purpose. Google search for the part number brings up several different images of the part, none that are similar. One of them appears to be a mechanical screw-in valve (possibly spring actuated) that might be part of the control valve body, and might explain the cause of this sudden failure. Has anybody on this forum had experience or knowlege of this older machine? This one has a single lever for lift (up-down) and tilt (forward-back) operation. As always, many thanks for any useful information. -Tom
Are you sure you're not getting fluid flow to the tilt cylinders? If no flow when actuated then it's probably a valve related problem. If you're getting fluid flow, then maybe you're bypassing in one or both cylinders depending on how your hydraulics are hooked up. Hopefully it's a simple check by disconnecting the return line on the tilt and seeing if you getting fluid bypassing the rod seals. Might have to check both cylinders since most tilts I've seen are tee'd off the one supply and return lines from the valve. Bypassing in one loses pressure for both cylinders. Also, I'd verify mechanical linkages are fully working if you haven't already done so. Rule out the simple things before going to the harder things.
Thanks for your input! I replaced seals in the two tilt cylinders 2 years ago as well as the lines going to the tilt lock valve. I just posted photos of the valve on my machine in the event you haven't seen them yet. Linkages are fine, and spools look like they're in normal position (no evident broken springs). I'll verify pressures before pulling the tilt lock valve to ensure that I'm not overlooking something. -Tom The two lines coming from the control vavle tilt spool are on the left, the tee'ed cylinder lines are on the right, and return is the center line. -T