Slow hydraulics on Ford 641D

This spring I bought a box blade and I have been amazed by the ease that I can remove large rocks imbedded in a chunk of ground I hope to clear enough to plow and put into some kind of production. I have used the box blade many hours removing rocks and digging a couple of ditches since I bought it. I also have used the loader to move a bunch of dirt that I loosened with the box blade. It has been kind of fun and I have the area nearly ready to plow.

My hydraulic system now seems to operate much slower than it did a couple of weeks ago. It will still lift the bucket filled with dirt, but it takes about 4 or 5 times as long. The box blade will still raise, but much slower than it used to.

I checked the hydraulic oil and found that it was quite white and somewhat foamy, kind of like a thin vanilla milkshake. The reservoir also appeared to be a little overfull. I suspected water and drained the reservoir with the 3 point down and the loader all the way down. I refilled the reservoir with the proper Ford spec hydraulic oil and found that the 3 point and loader soon operated a little better than it had been, but still much slower than a couple of weeks ago.

The tractor uses a 6 piston hydraulic pump mounted on the standard hydraulic manifold and the right side of the engine. I think I understand how the pump is supposed to operate, with a "wobble plate" pushing the pistons, which push the hydraulic oil out through the ball bearing style valves and out to the hydraulic manifold. Obviously the system is working somewhat, since the loader and 3 point will move, but I am wondering why it is working so much slower. To my knowledge there is no volume adjustment possible. The pump also doesn't sound any different than it ever did and neither the pump or the hydraulic manifold is leaking.

Could some of the pistons in the hydraulic pump have siezed up in the pushed position? That would explain why the volume of pressurized hydraulic oil seems to be much less than before. Could this have been caused by the water contaminated hydraulic oil, or have the piston return springs broken?

Should I remove the hydraulic pump? I doubt that it has ever been off the approximately 1960 tractor. I have never had a hydraulic pump apart before, but the directions in the manual suggest that it isn't too bad a job, and the only special tool needed is to remove the intake ball valve seats, which might not have to be done. Or should I have a good local hydraulic shop do the rebuild, partial rebuild or repair? Or should I look for some other problem that would cause the system to work so much slower?

This tractor sits out all the time. I changed the hydraulic oil a couple of years ago and at that time the old oil was pretty milky. I suppose the water has leaked in through the loader cylinders, which point up. Or maybe someone has messed with the tractor.... I will be keeping a closer watch on the hydraulic oil and hope to build a shelter for the tractor.

Nobody responded to these questions on the Ford board. Any hydraulic experts out there??? Thanks in advance!

This can save you tons of cash finding, or repairing the shaft itself.

If you go to a bearing supply site and get their seal catalog, you can update the seal to more modern materials that last longer.

Not only that, but you can use double lips seals that now protect the shaft from outside contaminates as well.

You also may want to pull out the pressure relief valve. This can be severely damaged by trash always pumped through it.
This will slow down all your hydraulics by lower flow output.

Take a good look at where the tapered poppet sits against the seat. I will bet you $5000.00 this point of contact is no longer sealing off oil flow like it should. This device should only flow oil at a preset value by it's spring and setting of it.

You can repair it easily as I have done, for $0 dollars, or pay out the nose trying to locate a replacement. Not including the time it takes you actually have one in your hand.

You already have all the necessary tools, and the system will work perfect again.

If you want to do this, and have a digital camera to do a real time event, then email me. After the event, then post here what took place.

Now, one other item update.
You can always spec out a hydraulic filter thats rated at twice the output you have and install it on the main return line.

It's the ultra fine metal particles that are forced past the relief valve that end up changing it's face. Like sand blasting of plywood, it look really cool, but wrecks hydraulics.
These same particles are also changing the clearance of the pump parts, making oil bypass some.

You see this on close inspection of the grooves left behind by repeated particles getting forced past the hardened steel components.

Another problem is that some systems on older tractors using the same oil reserve as the transmission. This will damage hydraulic parts to the extreme if not filtered.

Link
True/6401/Pumps

This link will show some pump designs as well as showing options.

Usually on swash Plate designs, the pistons are keyed into the plate to be pulled back and forth. To have them only on spring return would be unlikely.

Good Luck

Phil
Mpls Mn

Usually this design is for Hydrostatic transmissions, and gear pumps for aux hydraulics.

Also, what would the stick welder be needed for? I have one, but can't imagine what it would be used for with the hydraulic pump.

Unfortunately, my system does not feature a filter. I also suspected an intake leak, because of the foaming, but I thought it would leak oil out the same hole when the tractor is not running, which does not seem to be happening.

Thanks everyone for your help!

This will cause the white hyds.. and slow operation.. and will / can cause cavitation in the system which is detrimental to the pump.. etc.

If the oil whites and foams back up.. look for a leak.. ( or lots more water in the sump and system.. )

Soundguy