Swing arm stuck

[aswadthedog]

hi I was hoping someone could tell me why my jcb 801.4 1996 swing arm would be stuck. it wont go left or right. I have tried to release the hoses and move it with a jack, but no joy, I even tried to move the hoses to another control valve to see if it was the valve at fault but still nothing. ive had the digger for two years and soon after I got it, the cable to the swing arm broke and ive never been able to source a new one so ive been using it without a need for the swing arm. this means its been in the same position for all that time. any tips please and can anyone tell me where I can get a new cable. thanks

[Muz]

so its cable operated then ? Are you saying theres no cable attached to it at the moment ?

[aswadthedog]

no there is no cable connected to it at the moment but I did connect another cable that controls the arm to it which is the same and it wont move.

[Muz]

no there is no cable connected to it at the moment but I did connect another cable that controls the arm to it which is the same and it wont move.

Do you mean the ram wont move only .. or is the spool valve stuck as well ?

[aswadthedog]

the spool valve will only go one way but will not move the ram at all, I tried releasing the hoses and move the ram by hand but with no joy

[Muz]

the spool valve will only go one way but will not move the ram at all, I tried releasing the hoses and move the ram by hand but with no joy

Well the spool should 'centre' with an obvious detent ,.... and operate in both directions, but if it operates in one direction only, that would either fully open or close the ram, so , if its not operating the ram, and the digging arm is in its middle working position (I assume it is) then there may be a fault in the ram too, most likely the seal pack has come off from the end of the rod inside the case. It could also just as easily be a broken spring in the spool.

JCB rams are poor quality and the seal packs are only held on by a nut thats not very well secured.

Try reversing the hoses on the ram and operate the spool again... see what happens ?

When at rest in the centre position, usually about 1/4 inch of the spool rod is visible out site the block, when fully applied in one direction, all the chrome part of the spool rod dissapears into the block, and when applied in the other, about 3/4 of an inch is visible .. thats a rough guide to the amount of travel you would expect to see

[aswadthedog]

I tried to reverse it the other day but one hose was not long enough, I can push the spool valve in and it tries to pump but wont move. but if I try to pull the valve it wont move, I don't think its stuck in that position I think it just wont come out for some reason possibly because of the spring you mentioned. the swing arm is slightly to the left and not right in the middle but looks stuck, so it looks like ive got two faults, how easy is it to change the spring in the spool valve and repair the seal pack in the ram. can I weld the nut on the end to stop it coming off, will I need any special tools to do this job, thanks for your help so far do you know where I can get a new cable to operate it if I fix it.

[Muz]

I can push the spool valve in and it tries to pump but wont move. but if I try to pull the valve it wont move, I don't think its stuck in that position I think it just wont come out for some reason possibly because of the spring you mentioned.

OK.. lets keep this simple to help answer the problem,..

1 : how much chrome do you see on the spool before you push it in ?
2: do you hear the engine labour as you do so ?
3: when you release it, does it pop back out to the same position ?
4: are you certain there is only one cable going to one spool, and not two cables going to two spools to operate each side of the ram ?

[aswadthedog]

question 1. I can see 10mm chrome before I push it in. 2. the engine does labour when I push it in. 3. it pops out when I let it go. 4. there is only one cable that pushes then pulls. thanks

[Muz]

Ok so.. when the spool is operated in one direction, it may require the opposite side to close to get the ram to move, so all is not lost with the ram, it still might be ok, although I would have expected it to be operated fully closed or open, but it depends on the type of system your digger is using for its hydraulics.

If the spool is only operated by a single cable then the default position should be as you see it, where there is 10mm or so of spool showing, operating the lever one way would push all of that in as you describe, but the other direction would normally pull the same again out. So it would suggest something is trapped inside the spool housing, preventing it moving, or it has broken up inside the slice.

Dont panic .. it is serviceable but you're probably going to have to get the spool out to examine it, and that might not be so easy, depending on whats sticking it.

Before you go to the trouble, find the spool for the breaker circuit, move it in and out and observe that it goes in like the faulty one, but also comes out the way ?, as it will be a very similar spool, and let us know what it does ?

Ive added a pic for you to see what a typical spool rod looks like .. you can see its milled with lots of journals to allow oil flow through specific passages in the slice as the spool is moved in or out of that slice

IMG_2020.jpg

[aswadthedog]

hi I have looked at all the spool and they operate by going in then out, in this photo the bottom one is the stuck one (without a cable) and the top one is the one that controls the left hand trackdigger 2 003.jpg

[Muz]

Well assuming the spool should move in both directions ... The next bit is up to you if you want to do it ... or get a plant fitter if you prefer ? but the cap has to come off to get the spool out to examine it ...

There are risks here which may end up costing you and my advice is only a guide please note

You could chance it and do it in situ .. or take the slice off the block, but that involves a whole lot more work. If you take the slice off .. you must keep the others from separating it really needs to be done with the whole unit vertical to ensure the correct positioning of the 'o' rings that go between each slice. The tie rods that go though all the slices that hold the block together are also torqued .. so you will need the correct settings to rebuild it.

If its easy enough to get at, you can see the cap that holds the spool on, there's two little hex screws on it ... take them off and the cap should come off with a little spring pressure. I'm not sure what axis or plane you've taken the photo on, but get some clean rag and lay it under the cap as you remove it to catch anything that comes out with the spool if you are going to do it.

If its some metal that's trapped (due to a spring) and the spool or slice gets scored, it will render it useless, but you might have no option, hopefully it will be a bit of rubber from a hose delamination but just to warn you in which case, a whole slice with the spool already in it might be required. There will be top hats and springs at each end, and most likely some spacers, so be careful to maintain the order and orientation of them as you remove them. The spool may even be stuck fast.

Ive not stripped a JCB spool .. so I cant tell you the order you'll find the bits in I'm afraid. If you need a new slice .. have a wee seat before you phone for a price

Good Luck .. let us know how you get on ... if you're not confident .. get a fitter to do it for you.

*edit* TBH I cant see any tie rods holding the sections together, I hope its not a whole complete unit ?

[aswadthedog]

im going to see if I can get the end off before I go for a split, I did look at taking it off before but the bottom hex bolt was really tight. I think there is a tie rod through the block but im hoping not to touch it, ill let you know how I get on, cheers

[aswadthedog]

hi, I got that bolt off and it was seized on the end where the spring was and after freeing it up the valve moves freely again, (here come the but) but the swing arm still wont move, the engine labours both ways now meaning its trying to pump but wont budge, I guess this means its the seal pack now, this looks like a harder job but im ready for intructions, cheers

[aswadthedog]

hi, I got the ram out and gave it a clean and I moved it up and down and it moved freely so I fitted it back to oil and it still didn't work. is this the seal pack problem you were on about. I haven't taken it apart yet not sure how or what im looking for. will it be obvious when I get it apart. also while the pipes were off and with the valve in the middle position I started the engine and oil flew out of one pipe only is this right cheers