Blade leakdown on 40C

[JD40c]

The #76 blade on my 40C (yeah...wrong blade, should have a #61) leaks down fairly quickly, in about 7 ~ 10 seconds. Occasionally it will stay clear up. Would that indicate a worn valve assembly vs. worn/damaged cylinder seals? I loaned it to the previous owner for a couple of weeks and he commented on the blade dropping. I'm going over to help him move dirt next weekend so am trying to see if I can come up with a quick solution.

Looking in the service manual I have, it looks like the two valves in the hydraulic control valve are pretty simple, but the seat appears to be integral with the body of the control valve. Could I buy the two valves at a decent price and use a 35/45deg seat cutter to refurbish the valve seat (or whatever angle the seat is)?

Have any part numbers for the two valves? My service manual doesn't show numbers.

[Lavoy]

Jeremy,
If it is the valve, you can probably just "lap" the seats with valve grinding compound.
It seems to me that most of the time it is the cylinders that are bad. It is a little work, but lift the blade all the way up, and put a jack under it. Disconnect the hoses from the valve and cap the hoses. Let the jack down and see if the blade settles.
Lavoy

[JD40c]

Well after wrestling with the blade on my 40C, we finally pulled the cylinders off. When holding a cylinder so the piston rod is pointing up, it will drop on it's own very fast so I think the seals are TOTALLY shot. They are a pair of old Duke cylinders. Hopefully I can find seals locally.

[Lavoy]

Most of the time, the seals are fairly standard. If you have a good hyd shop locally, they should have them on hand. Be sure to check price on the parts though, the cyliders are a standard 8" stroke cylinder and are not expensive new.
Lavoy

[JD40c]

After pulling one of the cylinders apart, this is what I found:



The seal doesn't even stick out past the piston surface and the two backing rings are completely missing. $10 worth of seals per cylinder should hopefully have the cylinders back and rolling. The cylinder barrels looked good with no pitting or scoring. I couldn't feel any ridges with my fingers either.

[JD40c]

Well it should go without saying, but if you have leaking cylinders on your crawler, get them fixed! I think I spent a grand total of $13 in parts and my 40C has been transformed into a tractor that can actually grade well!

I flushed all the hydraulic fluid out by running the hoses for the cylinders into a couple large jugs, and kept toping off the hydraulic tank till fresh fluid came out the hoses. Feels good to have a machine that runs right again.