JD 93A backhoe control valve leak in odd place

[little1406]

I'm nursing along an old 93A backhoe attachment for my JD 450 track loader. Of course it leaks hydraulic fluid from multiple locations but the worst culprit are some little round things located on one or two of the control valves between the two hose connections.

this photo shows the overall control valve setup on this old hoe....

and this photo:

shows the little round things that are leaking. It's the cleanest one in this photo that leaks the most and, curiously (to me, anyway), it leaks when I pull any of the control levers, not just the one for that valve.

What are those round things? They don't have any feature to allow a wrench to unscrew them. They appear to be pressed in place. They do have a sort of lip that would enable one to pry them outwards but they seem pretty well stuck in place.

Any an all suggestions would be most welcome.

Thanks

Scott

 

[Zebrafive]

JD parts catalog shows a check valve in that location. I can't tell how it is retained in the valve body from the drawing

 

[little1406]

Thanks, Zebra, that almost explains it. I see an O-ring and backup ring right near the outside that are surely what's leaking in my case. But how does one get that check valve out of the whole valve block? I have a sinking feeling that I'll have to take the stack of valves apart and access something from the side that holds that check valve into the block........

Any ideas?

 

[Zebrafive]

Do you know the manufacture of the valve? They may have website or Tech help available.

 

[LD1]

Thats interesting.

I have never seen a valve that had a check valve like that where it wasnt obvious how to remove it.

Let us know what you find

 

[true temper]

They are held in with the tie bolt that holds the valve stack together. Might get lucky and be able to remove 1 bolt and the plug will come out. Replace them all while you have them apart. It’s an open center system and only leaks when you build pressure.

 

[little1406]

Thanks, True, I'll report back here if/when I get it apart. I agree on replacing o-rings in all of them.

 

[little1406]

Thanks a lot, gang. Removing the tie bolt did indeed release the check valves. They slide right out. There's even a little spring and irreplaceable square steel block in the back of the valve that you can lose when you pull out the valve.

Here's what the tie bolt looks like when it's halfway out (I had to drive it out with a long piece of 3/8" diameter steel rod):

And here's what one of the check valve bodies looks like:

The photo's a little out of focus on the valve but you can see that part of the backup ring is missing on one of the o-rings and the whole backup ring appears to be gone on the other o-ring. The tie bolt goes thru that dirty hole towards the outside and the other hole is the fluid port. The little spring hanging out the back presses a square steel block up against the backside of the axial port and that is the check valve. Both the spring and the steel square block are loose and liable to fall out when you remove the valve from the body. As usual, I don't understand where the fluid is going in this valve but at least I know to replace the o-rings. Looking at the grooves, it appears to me that the factory installed fairly skinny o-rings with backup rings. I wonder if I could get by with fatter o-rings alone that fill the groove more completely?

Thanks again for the valuable advice. This strikes me as a rather unusual assembly and I doubt if I would have ever tried driving out that long bolt without yall's advice.

 

[little1406]

I spent some time measuring the bore and the groove diameters on these check valves. Interestingly the bore is stepped, 1.126" diameter at the mouth, 1.092" diameter halfway in where the ports and the first o-ring are, and 1.060" diameter towards the back where the 2nd o-ring is.

The first o-ring is a -118 (this is confirmed from the JD parts list for this check valve)
the second o-ring is a -021 (not confirmed from any parts list but clearly the correct o-ring from the gland dimensions).

I ordered these o-rings in Buna 70 and also Buna 90 backup rings from the Oring store.....$30 including shipping.

I'll make at least one more report here on the degree of success I achieve with this repair.

 

[little1406]

Final report. The o-rings and backup rings arrived today and they fit nicely. I put everything back together after first marking each check valve with a line across the outside surface that aligns with the bore that the retaining bolt has to go through. That way, once I had pushed them all back into place I could rotate them (with pliers) until they were properly aligned for the long bolt. They were a bit difficult to get seated all the way back into the bores. The last 1/4" or so of travel is where both sets of o-ring seals have to enter their final bore diameters and I had to use makeshift leverage to force the valves past that hard spot. I tried to be as gentle as possible to give the o-rings a good chance to go correctly into the bore instead of getting pinched disastrously. Despite all my alignment efforts, I still had to drive the retaining bolt in with a hammer in some spots. But the threaded end came through more-or-less unscathed and the nut fit back on easily.

The real good news is that this repair fixed all those leaks I had before. I'm going to have to get used to a machine that doesn't take a whole 5 gal bucket of fluid every time I use it....

Thanks to everyone who produced the valuable information I needed for this repair. I hope this saga is useful to others in the future.

Scott