Im a paper-pusher with a large JCB backhoe (14 years)and today there was a "pop" while I was using bucket/thumb (closed) to push dirt (maybe hit concealed stump)Unable to open bucket/thumb...I assume seal popped. Ram Pressure remains in system to force thumb closed regardless of valve position or engine off. To remove ram to take to shop do I let fluids slowly bleed? If so, does this result in system air and bleeding problem later? thx Rand

Is it leaking oil? If so where from? Check the hoses, you may have only blown a hose.

No(abnormal)leaking in entire system; hoses appear normal; thumb/bucket/ram connections appear normal (no binding)...my crowbar forces thumb-bucket apart an inch...but clear ram pressure forces it closed regardless of valve operation. Its a large ram (this is a 16000# hoe)and working pressures are at 3000# I believe. I assume since I have had broken hoses before and no air-bleed issues...that it wont be any different if I bleed pressure off in order to setup and remove the ram?

Sounds more like the Valve Spool separated and allowed pump flow to go to the cylinder continuously. Just a thought, especially if the "Pop" sound close.

There can be a problem with air in the circuit when you start it up after breaking lines and installing an empty cylinder.

You could fill the cylnder as much as possible before starting the hydraulics. Then the air in the lines that were opened will have a better chance of getting back to tank.

Bud, appreciate your perspective re the valve. I think the "pop" was out near the bucket-ram. Is there a improvised diagnostic I can try to focus on the ram...since pulling it and taking it to "town" and back will take eat up 3 or 4 days?

--Or, at top of dipper, along connections for the bucket-ram, there are also two hose connections to dipper-ram, I assume I cd switch those over to the bucket-ram (leaving bucket valve disconnected) and use that dipper-hose system to test the bucket ram?

Our rural part of the state does not have ready access to mobile repair. Im not experienced in this stuff.

rand

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I would remove the hoses at the ram (Cylinder, Double Acting I believe) and hook the hoses together or to a known good cylinder, and see if pressure drops off and shifting the valve gives flow in both directions at varied rates. If there is controllable flow then it is'nt the valve and your in for a trip.

If the problem is still there you have a valve or hose problem if there are no other valves in between the Directional Control and the Cylinder.

Bud, when(excuse ignorance)I hook hoses "together" I assume I should use some pressure gage in between...Is that the point? (If Im not installing another good ram).

And sloppy observation on my part: the ram system fluid source I cd switch to wd be the extendable-hoe ram, not the dipper ram.

This is a JCB...(English) and the connections are not the standard flare...switching out connections via the extendablehoe-ram system is easiest...Is there a reason to not do that (generally)?
rand

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quote:

Bud, when(excuse ignorance)I hook hoses "together" I assume I should use some pressure gage in between...Is that the point? (If Im not installing another good ram).

A pressure gauge would show if there is a restriction in the lines. Otherwise, pressure should be low.

And sloppy observation on my part: the ram system fluid source I cd switch to wd be the extendable-hoe ram, not the dipper ram.

This is a JCB...(English) and the connections are not the standard flare...switching out connections via the extendablehoe-ram system is easiest...Is there a reason to not do that (generally)?

If I understand you mean to hook the lines from the valve on the non=operating circuit to another cylinder you will still be able to tell if the valve is good. In fact it is probably the best of two options I offered.

No that isnt what I meant.
I was suggesting isolating the potentially bad valve (leave it alone)since if I connect my extend-ram to that valve and the valve is bad...I end up with a high-pressure extended hoe.

It wd seem best to connect the suspect bucket ram to the operating valve normally used for the extended-hoe. We know that valve works. If suspect bucket ram works while controlled by the extended-hoe valve, then we know its the other valve/if the ram remains in the extended position, we know its the ram.

And I greatly appreciate your time. I've always wanted to delve more into fluids...but not quite while I was broken down.

rand

Take a look at my Ebooks on the home page of this forum to get a start in Fluid Power. THe Basic book willl give you a background in Hydraulics and Pneumatics. I used it to teach Mechanical Maintenance Journeymen ans Apprentices, Electrical Apprentices and a few Journeyman Electrical persons over the years.

Another guess might be that you have bent the rod and or popped the piston off of the rod. Just a guess as i'm not there to see it!

I appreciate your responses...I will find some plugs for the lines, then switch supply valves and see what I get.

Great E-book...matches my $400JCB service manuals but with greater detail, logic and context.

rand dawson Oregon

For those interested:
I switched hose sources...and the ram/cyl still didnt function and the original valve did work--so problem was in cyl...and guess is the "pop" was the piston top blowing off -- or one hydraulic shop said an "O-ring"...So we will find out.

thx for comments.
rand in Oregon