Thumb Valve Leak Mystery

[mmranch]

I have a new tractor with backhoe and the backhoe has a new Wallenstein thumb installed. All works great but the thumb valve has developed leaking problems.

Basically, I don't use the thumb very much compared to the backhoe itself and after awhile, the thumb valve leaked from the piston on the bottom that is connected to the foot pedal. The tractor dealer contacted Wallenstein and they sent a new replacement valve. (The dealer thinks it's new but I have my doubts).

The reason I have doubts is that the valve, rather than being painted solid black, looks like it was painted black but then the black rubbed off and only remains down in the tiny crevases of the metal surface so the valve is sort of silvery black. The valve has 4 hydraulic connectors where the fluid goes to the valve. Three of the connectors are identical as far as the nut that tightens the connector to the valve body but one connector is a slightly thinner nut and appears to have a different metal color (this is the second reason why the valve could be a refurbished valve... I could be wrong about these susupicions).

Anyway, the dealer installed the new valve and delivered the tractor back and after a short while, this one different hydraulic connector developed a small leak. I examined the connector closely and it appeared to have a piece of O-Ring hanging out from under the washer by the valve body. I loosened the connector nut and pulled out the piece but there appeared to be more O-Ring still under the washer. I notified the dealer of the problem and he sent some replacement O-Rings but in the meantime I tightened the connection again and the leak has stopped at the connector.

But a short while later, the valve began leaking again, this time from the small piston on the bottom that connects to the foot pedal... just like the first valve. It started small with a droplet that ran down the pedal rod but has progressed to a much greater flow and now is leaking a lot and there is now a tiny fragment of what looks like an O-Ring piece that is hanging out from next to the piston. I have notified the dealer and he is checking with Wallenstien about what they want to do about it but I haven't heard anything back yet.

I have attached a picture of the small piston that is leaking and there are two hex screws that appear to hold a plate around the piston. Is there an O-Ring that lives underneath that I can change out or something?

Thanks for any ideas!

Mike

 

[kennyd]

Welcome to TBN Mike

There very well could be a o-ring or packing under that plate that keeps dirt out of the spool. Not sure what other advice I can offer...do you know the maker of the valve? Any numbers on it?

 

[mmranch]

Thanks for the ideas. It does have a plate on the valve with SN, etc. I will check the info when I go out to the shop.

 

[mmranch]

OK, I got some info from the thumb valve plate. The valve manufacturer is Salami... made in italy. The (model?) number appears to be VDM6/D/U45. Then is has a (serial?) number 62310041114...

So far, I haven't found this particular valve in my searches.

I'm not sure what to call this valve but it only makes the single thumb cylinder extend or retract.

Thanks!

 

[mmranch]

(I know very little about hydraulics/valves).

If I were looking for a replacement valve, what would I call this type of valve?

The valve body has 4 hydraulic hose connector ports (all on one side of the valve body) and a little piston on the bottom. The piston can go in towards the valve and pull out away from the valve and this piston connects to a rod which connects to a rocker pedal. Two of the hydraulic connectors send hoses to the thumb cylinder and the other two connectors send hoses to the hydraulic system.

Thanks!

 

[mmranch]

OK, I've made some progress. I took off the cap on top of the valve and this let me pull the entire piston (spool?) out from the top. Then I removed the plate from the bottom of the valve and this revealed a metal washer and O-Ring down there. This O-Ring had some damage and this was where the leak was coming from. I replaced this lower O-Ring and put it all back together and ran the tractor for awhile and it didn't leak in my short test.

Still have to work the tractor under pressure to see if I've stopped the leak.

Thanks!

 

[kennyd]

OK, I've made some progress. I took off the cap on top of the valve and this let me pull the entire piston (spool?) out from the top. Then I removed the plate from the bottom of the valve and this revealed a metal washer and O-Ring down there. This O-Ring had some damage and this was where the leak was coming from. I replaced this lower O-Ring and put it all back together and ran the tractor for awhile and it didn't leak in my short test.

Still have to work the tractor under pressure to see if I've stopped the leak.

Thanks!

Good news MM. Hopefully that fixed it.

 

[mmranch]

I just worked the tractor/backhoe for about 4hrs and there was no leaking... so it looks like the O-Ring was the problem and now it's sorted.

Thanks!

 

[mmranch]

Unfortunately, this problem has continued to plague me. According to the dealer, Wallenstein simply wants to give me another valve of the same brand. The first and second Salami valves have failed in the exact same way so I doubt a third valve will fix the problem.

The dealer is currently getting a different valve to try to solve this problem but in the meantime, I am changing out O-Rings every day to try to get some work done.


The Salami valve is very simple in design. It is oriented vertically and has a single spool (which the pedal rod moves up and down). On the bottom (where the pedal rod connects) there is a plate which holds a single washer which holds an O-ring. The valve body is machined so that there is room for only a single washer and a single O-ring. On the top of the valve, the spool is attached to a spring with a screw-on cap over the spring. Again, the top of the valve body is machined to hold a single O-ring.

As the spool moves up or down... the O-rings are supposed to stay in place hugging the sides of the spool.

Problem is, something is damaging the O-rings. When you look at the bottom of the failed valve, there will be a peice of O-ring hanging out. Or (if no O-ring hanging out) when you take it apart, the O-ring will still be in place but will have chunks missing. The upper O-ring (on the top of the valve) will show the same problems. It's like the spool has moved too far and the O-ring is scraping against where the spool narrows.

The problem with this theory is, there have been many times where I am using the backhoe only and never use the thumb pedal at all... so the spool should not be moving at all yet the valve will fail after a couple hours of use.

I have tried every configuration imaginable including softening the edges of the washer, removing the washer entirely and putting 2 O-rings on the bottom (so there is no washer to scrape against), putting 2 O-rings on the top, flipping the bottom washer, limiting pedal rod movement, etc.

Nothing will keep the O-rings from being damaged and the valve leaking. It's very difficult to get any work done with hydraulic fluid leaking all over my boot!

Hopefully a different brand of valve will fix the problem.

 

[mmranch]

Just an update to this thread.

My dealer installed a Prince valve for the thumb and there is now no leaking at all. Thanks Devin!