Replacing Hamworthy Check Valves on JCB Backhoe

[LN Pipeline]

My JCB 214S backhoe has significant cylinder drift in all loader functions - lift, shovel, and clam cylinders. Both clam cylinders and one lift cylinder have been resealed. Lift cylinders can be fully extended and the bucket will drift all the way to the ground within minutes.

I pulled the Hamworthy valve block to replace the check valves, and found that they are metal on metal, with the check valve seat being machine into the block.

Has anyone had any luck with this type of check valve holding 100% after replacing? It seems to me that there is likely wash on the non-replaceable seat in the block.

See pictures.

The grooves in the check valves seem to be from wear.

 

[thepumpguysc]

I can see why they're drifting.. do they sell JUST the check valves??
IF they do.. I would tack a rod to one of the old ones & lap the hellouta the seat, using valve lapping compound.. Couldn't hurt.. AND replace any springs..
Good luck.. WE ALL KNOW what a PITA a drifting cylinder is.!!!

 

[LN Pipeline]

I can see why they're drifting.. do they sell JUST the check valves??
IF they do.. I would tack a rod to one of the old ones & lap the hellouta the seat, using valve lapping compound.. Couldn't hurt.. AND replace any springs..
Good luck.. WE ALL KNOW what a PITA a drifting cylinder is.!!!

These individual parts are available through JCB, but are expensive. I just sent the part numbers to Hydreco to see what they come up with.

I considered using lapping compound, but I’m doubtful it will result in a leak proof seat. I foresee doing this, installing new parts, reinstalling the valve block, and still having drift.

Having a machinist carefully cut a new face with a mill seems like the only way to get a proper seat, if the seats are in fact bad. Is it possible the check valves are made of a softer material so they wash without damaging the seats? Can I simply install a new check valve and have zero leaks? Doesn’t seem likely, but maybe. Are these valve blocks intended to be thrown away after they get a little wash? Has no one else encountered a similar problem with similar components and remedied the problem?

 

[heymccall]

You've got the manifold out. I'd just enlarge the seat hole enough to allow seating on the none groove portion of the plunger.
Should be soft enough to use a reamer.

 

[Billrog]

I'm not so sure that's causing that much drift ( in so many places)you'd think that much wear would be visible. Are the springs seating them. Never worked on a JCB so not much help but any old valve bodies I've taken apart to remedy a drift it's always been an O ring or something loose never the metal to metal plungers I've never seen metal seats like that though as far a I can remember.

 

[TVA]

Kinda look like the ones on Parker monoblok control valves, they used with weak springs and rely on the pressure to seal. I’ve seen them on many forklifts and loaders.

Not long ago ( couple of months) I worked on one of those DCVs, machine was made between 1970 and 1976, but the valves was not nearly as bad as these! For me it looks like excessive oscillation damage, probably was making screeching sound a lot.

 

[thepumpguysc]

U should be able to LOOK in the block at the seats.?? I would think the seats would be harder than the valves.?
Its looking like your on your own w/ this one.??
& yes on the drifting/leaking cylinders being an Oring in most cases..
Are there springs holding the valves on the seat.??

 

[LN Pipeline]

The seats look good, but I can’t say for sure if they are perfect. There are no O-rings involved in the check valves, aside from the ones on the caps that seal to the exterior, shown in the picture. Service manual nor parts book show any O-rings. The picture shows the check valve and cap, and there is a small spring between the two.

Considering the amount of drift I have, I also thought I’d find more damage than this.

I’ll mess with this thing some more next week, and report back when I get something figured out.

 

[LN Pipeline]

I figured I’d report back since this issue has been remedied.

After buying a few British thread fittings, I found the majority of my drift was coming from a bad internal ram seal.

There is still drift, which appears to be from oil leaking past the spools, and is apparently considered “normal”. The spools do look perfect. All other ram seals held pressure.

Out of curiosity, I priced a new 3 spool loader valve through JCB. They want over $4300. Seems steep.

 

[jcb jeff]

The valves in the picture are load hold check valves they make sure you have flow/pressure behind them before allowing oil into service selected as these came from between the the outlet pipes correct.
The long valves on the ends of the block next to the spool end caps and lever controls will be the arv or aux relief valves these often cause issues.
Have you blanked the rams and done a load hold that way to confirm rams are good.

 

[LN Pipeline]

I did test each ram with a hand pump and pressure gauge. That’s how I determined the one lift ram was leaking.

Thank you for the explanation on the check valves. After further studying the service manual, I assumed this was their function, and I just put them back in as they were.

I tested the three spools with the hand pump, and bleed off was pretty much the same for all three. I described this to the local hydraulic shop, and they said it was probably normal. I am convinced it is, since there is no relief for the lift function, yet it bleeds off the same as the other two with ARVs. I didn’t test the ARVs, individually.

It’s back together, and I’ll continue using it like it is.