MF40 Industrial power steering problem

williams1708 · Aug 24, 2017

I am re-working the power steering on my early 70's MF 40 Industrial tractor. When I bought it, it had a Barnes style pump mounted to the engine, but it was missing the fittings and the lines were hanging. The pressure line comes out of the front center of the pump and goes to the Char Lynn orbital steering control valve with 4 ports. I can't tell which port is the pressure port and which is the return port. The diagram in my re-print parts manual is not clear enough to show it. I would greatly appreciate it if someone with an MF40 or a good parts manual could take a look and let me know which port it is. It should be either the top or bottom left side port of the control valve, when looking from the front of the tractor.

williams1708 · Sep 3, 2017

I figured out the pressure line connects to the lower left port and the return line is the upper left port as viewed facing the ports on the orbital control valve.

PatrickS2222 · Sep 9, 2017

Great to know you've made progress. Presuming you've got it back together, does it work well now?
Any pics would be greatly appreciated - I'm about to reseal everything in my MF40 - it leaks everywhere - a reservoir full in around a half-hour!

williams1708 · Oct 18, 2017

Yes, I can steer with one finger... I had to rebuild the hydraulic cylinders and reseal the orbit motor (aka control valve). You can buy a new pump for $100, but the orbit motor and cylinders are pricey. If it steers fine, but just leaks, you can buy the seal kits for the pump, orbit motor and cylinders cheap. Just takes a little time.

PatrickS2222 · Oct 20, 2017

Great result, and I'm aiming for the same outcome. :thumbsup: You should enjoy driving it now. :laughing:
As you say, seal kits and time will take care of the leaks. I believe my pump is Ok, it has light steering while there's oil in the system, but leaks a bit. The other issue I'm facing is worn joints on the cylinders - I have to find out whether replacement joints are available, otherwise have them rebuilt (a rather pricey process) or come up with another pair of cylinders with reasonable joints on them.

williams1708 · Nov 5, 2017

I know the joint on the rod end is replaceable, part #1033035M92. I don't recall if the barrel end is threaded or welded and the parts diagram doesn't show it well. These diagrams aren't always accurate either. Either way, the joints are standard size and easy to get, but you may have to weld-on the barrel end. As long as the rods are good, cylinder rebuild is easy and cheap. The rods on mine were rusted/pitted and had to be replaced, ended up spending $200 per cylinder. The cylinder joints were good though, just had to replace the boots. Tear one down and see what you have. There are a few of these in the salvage yards.