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Thread: JCB 8018 dipper issue

  1. #1
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    JCB 8018 dipper issue

    Hi, I'm new to the forum and have recently purchased a 2008 JCB8018. It worked fine for a short while before 3 services stopped working - LH track, Dipper, Aux. I tracked this down to a piece of swarf keeping a valve open on the track slice of the valve block. Having cleaned it and re-installed it I've found that the LH track works fine, the Aux dead-ends (I don't have an attachment) and the dipper does not work, but it does appear to dead-end. Strangely, when I dead end the Aux (in either direction) the dipper works fine.

    If I try using the dipper on it's own I find that if I've moved the boom the dipper will settle to a natural vertical position. Note that this only happens if I use the joystick, otherwise the dipper is locked in position. This suggests the spool valve is working fine. When I max out the position of the joystick, either forward or backwards the dipper appears to dead end or, I'm assuming, the MRV kicks in. I've checked pressures on servo and MRV's and these are fine. I've swapped out ARV valves on top part of dipper block, but not yet done bottom ARV/Anti Cavitation valve.

    I'm not a mechanic, but 've managed to get this far with the service manual and google, but now I'm stumped and I've ran out of talent! I don't understand why it would work if the aux is dead-ended but otherwise it does not. Does dead-ending the aux create a different fluid flow or pressure in the dipper block?

    My plan this weekend is to swap out ARV/Anti Cavitation on bottom of dipper block and then try swapping pump 2 with pump 3. Although I tested the pump back when I had initial problem and it seemed fine. Anyway, I'll try again. I'm pretty sure there is no air in the system but wonder if there is a way to check this.

    If anyone has any other ideas I'd be pleased to hear them.

    I'm also attaching a picture of the hydraulic circuit for these 3 services in case it helps. The valve circled is where I found the swarf, which essentially kept the valve opened and straight back to tank. I'm now thinking the non-return valve into the dippoer next to the pink line may be the problem, but I don't understand why dead ending aux would allow the dipper/arm to work.

    https://www.dropbox.com/s/gw8u67flyg...vices.jpg?dl=0

    If anyone needs the full hydraulic circuit for 8014/16/18 let me know and I can try put it up in dropbox.

    Thanks for any help.

  2. #2
    Admin Muz's Avatar
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    Quote Originally Posted by vfr98 View Post
    I don't understand why it would work if the aux is dead-ended but otherwise it does not. Does dead-ending the aux create a different fluid flow or pressure in the dipper block?
    Hi & welcome to the forum .. I assume when you say dead end the aux, you just mean opening the valve, as there is no service attached to it ? What in effect you will have done there is to create a pressure inside the aux slice that will blow a main relief. The architecture of the block may be that high pressure oil can escape to another service, which is why you find the dipper working in those circumstances when you open it simultaneously. It may also be that you haven't refitted the slice you removed quite correctly, or with all its o rings in tact.

    Are you certain there isnt another fault inside the dipper ram it self ? can you take a pressure reading in line to it to confirm there is/or is not a supply to it ?

    Also .. check the pilots are moving freely up at the handset, so that they are opening and closing correctly for the dipper circuit ... it wouldnt be the first time Ive been caught out with that Could also be more dirt somewhere else ofcourse
    Please don't PM me for plant advice.. thanks .. Post in the forum where I will gladly help, as will many of our contributors.. as the info and responses will help everyone else, which is why we exist

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    Quote Originally Posted by Muz View Post
    Hi & welcome to the forum .. I assume when you say dead end the aux, you just mean opening the valve, as there is no service attached to it Yes, correct, but the valve needs to be fully opened and the MRV blown as you say? What in effect you will have done there is to create a pressure inside the aux slice that will blow a main relief. The architecture of the block may be that high pressure oil can escape to another service, which is why you find the dipper working in those circumstances when you open it simultaneously. that makes sense It may also be that you haven't refitted the slice you removed quite correctly, or with all its o rings in tact. Really didn't want to hear that....but it has crossed my mind I might need to take it all out again and if I think back, one of the seals on the aux wasn't sitting properly compared with other slices. Can't remember if it was against the dipper slice or on the other side.

    Are you certain there isnt another fault inside the dipper ram it self ? can you take a pressure reading in line to it to confirm there is/or is not a supply to it ? I did wonder this, but because it seems to work properly when then aux is opened I'm thinking (hoping) the ram is ok. I'll look into this over the weekend too.

    Also .. check the pilots are moving freely up at the handset, so that they are opening and closing correctly for the dipper circuit ... it wouldnt be the first time Ive been caught out with that Could also be more dirt somewhere else ofcourse
    I'm thinking more dirt or something is imploding elsewhere.... I've been giving it some thought this afternoon and I think my first port of call will be the check valve to see if it has been jammed by dirt.

    I'll let you know how I get on.

    Cheers

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    Admin Muz's Avatar
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    Quote Originally Posted by vfr98 View Post
    I think my first port of call will be the check valve to see if it has been jammed by dirt.I'll let you know how I get on. Cheers
    I'm not familliar with 8018's , but usually check valves are fitted to ram entry points as fail safes so that, in the event of a hose failure, the ram cannot collapse. Usually they are in a block at the ram base. Many systems now however are fitted with 'shock' valves to remove sudden system loads, not sure if its this you are referring to ? but if it is, I'd suggest it to be unlikely to be the fault, (although you can never be sure) as by one means or another, you 'have' had the circuit operating, It sounds more like a plumbing problem, or possibly a ram fault, in which case switching the hoses to another ram to test the circuit, would remove this as a possible fault.

    I havent looked at the schematic in detail, but usually services are grouped, as you will have 9 or so being in no particular order LH/RH track, Dozer (3) boom dipper, bucket (3) aux,offset, slew (3) . Groupings are designed to promote functionality of the digger, ie slew wont usually be grouped with boom lift or dipper so that oil wont be 'stolen' from either of the other circuits so as those functions can be operated simultaneously .
    Please don't PM me for plant advice.. thanks .. Post in the forum where I will gladly help, as will many of our contributors.. as the info and responses will help everyone else, which is why we exist

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    Hi and welcome fellow 8018 owner!!! I can't help I just get the mechanic out! But welcome once again!

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    Quote Originally Posted by Wee Jim View Post
    Hi and welcome fellow 8018 owner!!! I can't help I just get the mechanic out! But welcome once again!
    Just a a few questions if I may? Did you remove the spool slices? And if so did you remove the block from the machine?

    Mick

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    Quote Originally Posted by Wee Jim View Post
    Hi and welcome fellow 8018 owner!!! I can't help I just get the mechanic out! But welcome once again!
    Cheers Jim. Hopefully I'll be a fellow, fully working, 8018 owner soon

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    Quote Originally Posted by Mick-the-fitter View Post
    Just a a few questions if I may? Did you remove the spool slices? And if so did you remove the block from the machine?

    Mick
    Hi Mick, I did remove the spool slices and whole block from the machine. I tried to be careful with plugging hoses and keeping it clean. I did wonder whether a slice was cracked but couldn't see anything but did find that little bit of swarf where I thought it might be.

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    Quote Originally Posted by vfr98 View Post
    Hi Mick, I did remove the spool slices and whole block from the machine. I tried to be careful with plugging hoses and keeping it clean. I did wonder whether a slice was cracked but couldn't see anything but did find that little bit of swarf where I thought it might be.
    Ok, There are a few things you can try, the long bolts that go through the block can be over tightened or of different torques, therefore the spools can simply not move freely and may jam up, also I would trace back dipper and aux hoses to the spool and make sure you have both dipper hoses on the same spool and both aux hoses on the same spool!
    Another thing you can try to get a better idea of what is going on is to take the hoses of the boom ram spool and change them to the dipper spool.

    Mick

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    Another fault Ive seen on some modern blocks, is 'o' rings going hard ... if the block gets hot regularly, some o rings lose elasticity, and particularly after they have been moved, or the block disassembled, they don't take up the variance in the mating surfaces that they should, once its been re assembled.
    Please don't PM me for plant advice.. thanks .. Post in the forum where I will gladly help, as will many of our contributors.. as the info and responses will help everyone else, which is why we exist

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