Hydraulic leak from main valve block.

Hi all,

I was removing a pool with my js240 when we notice a severe hydraulic leak. Upon closer inspection it seems to be coming from rear top section of the main control valve. Does anyone have experience with leaking control valves?

I thought the block was pressed together with a gasket running down the centre but according to schematics there is no gasket, just a load of Orings.

The Orings set I priced at $300 ex UK

We are going to attempt to repair this ourselves but just seeking some advice before we begin tomorrow.

Thanks and regards
Andy

Since I have not received a reply I assume there may be a lack of experience with main control valves.

I shall thus share my experience.

Machine is a JCB JS 240


Sprung a hydraulic leak the was coming out of the join between the two halves of the main control valve. Leak was unacceptable at approx 1 litre per minute.

Not bothering to even consult the price from an "expert". I began the task of removal myself.

Hoses were easy to remove but access not always so easy. Simple 17mm & 19mm spanner, and two hex head (forget the size) was all I required for the whole job. Every hose should be labelled upon removal, either with your own drawn up diagram or the diagram from the repair manual preferably. Zip tie the hoses in their clusters and move out of the way.

Undo all the large pipes and mark them also, however as they stay in their position and are just merely unbolted it is easy to know where they go.

Once every hose, pipe, and the 3 electrical plugs were removed, I undid 4 main bolts holing the valve to the chassis frame.

I then drove my crane truck along side and carefully lifted the unit out.

Once out, just had to undo 8 bolts holding the two halves together and it opened up to reveal the broken Oring inside.

Best to replace all of them including the one that looks like a blank! I skipped the blank as I thought it was a mistake during manufacture, I was wrong. After another 5 hours putting it back in the machine it leaked worse than before.

I had to begin the whole process all over again.

This time I have taken it to a shop to get pressure tested as I do not ever want to have to do this again.

All in all, the take out process for a complete novice was 6 hours. The return, 4.5 hours. The second time I took out I did in 5 hours.

orings JCB Dealers $190. Seal shop in Perth. $48, Pressure test, to be completed today but quoted approx 4 hours @ $90 per hour.

Sorry about that antpoo that I didn't catch your original post back in November. Looks like you're knee deep in a crocodile for sure. Yes, it's not uncommon for those o-rings that seal the valve sections to go south and cause a leak, and I hope the replacement of these o-rings will sort out your problem. If it does, there's a "however" that comes with it. Typically, with o-rings, the two most common failures that cause a leak is 1), fatigue that causes the o-ring to blow, and 2) age, o-ring becomes hard from age and heat, no longer has elasticity, becomes hard as a brick bat and can no longer flex to make a seal when under pressure. If it's suffering from #2, then I would suspect the valve spool seals as well, moreover, every o-ring or seal pertaining to the main control valve, I'd replace all of them. But some nice work you're doing, looks like you have the situation under control.

hello all,

i am really in a pickle now. i have had control valve returned after pressure test. $660. Unfortunately, the leaking hydraulic oil over the last 8 days has destroyed my white massing tape and the numbers are unreadable. i took a stab and put them where i thought they belonged, but when i started the engine the machine began to move by itself. i panicked and shut it down before seeing if there were any other involuntary control movements.

my question is thus. Would the track moving indicate a pressure hose being placed on to a pilot controlled spool? does that even make sense?

i believe the joystick pilot valve allows the spool to open and cause a machine part to move. does this mean that if i take off hoses that are controlled by a pilot valve that oil will not flow from it unless a movement is mad from inside the cabin?

i now have to find a way to correct the hoses in the wrong place through trial and error and i would greatly appreciate advice if anybody has any.

thanks and regards
andy

What is your serial #

Hi mike,

I do not have th serial as I'm not with machine right now. I do have the full repair manual for it and all schematics, but tring to follow the hoses is an arduous task, most of hoses are close to length and you can pretty much guess where they go accurately. Obviously however I have one or two wrong and I am trying to figure the best way to solve this problem by removing hoses, manipulating the control to find out which hose it is and then putting in correct position.

I just need clarification that when I take of a pilot controlled hose from control valve that no oil will fly until the console input is activated from inside cabin.

Anyway I will be heading down soon so I'm just going to give it a go.

The only way any function moves is the spool has moved. No other way, so that means there is oil pressure to the spool. Unless you are using the hydraulic schematic from the service manual, do not use a parts diagram to determine hose location. As was mentioned by Willie59, you should also replace any fitting o-ring as it has been in the same heat as the ones you are replacing. Don`t cut corners now while the valve is on the bench. The next o-ring that will leak will be the one you can`t get to with the valve in the machine.

antpoo said:

I just need clarification that when I take of a pilot controlled hose from control valve that no oil will fly until the console input is activated from inside cabin.

Click to expand...

In theory you're right, however when the pilot valve is neutral, the hoses will be drained to tank so you might get leakage to a greater or lesser extent depending on if the tank is pressurised and the bore/length of the pilot hoses.

Dang antpoo, wish I could help but I got nothing on a JS240. All I can offer is for future repairs, I typically use a center punch to mark hose connections. The first hose I take loose I punch a dot on the hose fitting and the adapter fitting it's connected to. The next hose to come loose gets two dots from the center punch, you get the idea. Punch marks don't wash away, pretty much a permanent mark. Upon re-assembly simply connect the dots. I hope you get it sorted out.

My advice is this . What you can do is disconnect the pilot line going to the tracking valve . and basically see which one is in the wrong place after that . it will be a lot easier if you take what you know is on there wrong out of the equation totally . you should also do a quick check with the machine on to see if anything else is out of place ... just ensure you keep revs low and your surroundings clear just in case .. I highly doubt a control line could be mixed up with a function line that easily .

what would also help is to see what will happen when you operate the function/lever that is suppose to move the function that moves on its own .

Thank you everybody for replies. Unfortunately they were a tad late and I just went to my property and took a stab at it. (By myself I might add, it can be done).

So it turns after disconnecting all the track forward/reverse hoses I found the one that was pressurising and making track move by itself. Was a hose that was supposed to be going to tank.

The other hoses I figured out by manipulating controls while they were undone and with my iPad pointing at the area on video to be my second set of eyes. When I manipulated a control and fluid flowed, I knew where hose needed to go by referring to schematic.

Go pro on wifi onto your iPhone or iPad is an even better way to view.

So after 2.5 hours machine is fully functional and fingers crossed, no apparent leaks.

Turns out we dont need to pay $100 per hour after all.