The Craftmans Shop > New from Old
It's BIG, Yellow and digs holes! JCB 3CX Project 8 is joining the Tractor Shed
awemawson:
When I got this 3CX there was a slight leak from the 'Auxiliary Valve' - this is a foot operated valve that would operate a hydraulic breaker were one fitted, but on my machine operates the 'ExtraDig' dipper extension slide that gives an extra few feet of reach.
As I played with the machine the leak got a bit worse and I decided that it needed sorting. It was a check valve that was leaking - a simple cylindrical body crossed drilled for one of the bolts that hold the slices of the valve together and thus retained in the valve. This body has an O ring and backing ring to seal to the body of the valve and has a spring and clack valve pressing onto a machined surface for it's check valve function.
Internal spare parts for this valve are 'no longer available' from JCB or the various parts dealers, however I was able to find a good secondhand valve which I got my hydraulic fitter Martin to put in, his flexibility being considerably greater than mine. It only needs a mechanical pedal linkage removing along with four hydraulic hoses and some mounting bolts - technically trivial but physically impeded by loads of other bits of JCB surrounding it!
Needless to say after a few months of operation the replacement started leaking in exactly the same way :bang: I tolerated it until recently while ditching I burst a hose on the Extradig circuit and when replaced the valve leaked hugely. Probably the extra pressure pulse had destroyed the O ring seal.
Well - this time I still had the original valve so could dismantle it to measure O rings, backing rings etc - slightly odd ball sizes but I am sure that I could have found them from the myriad of hydraulic suppliers that are on line.
In an idle moment one evening I searched for 'Check Valve' on the official JCB parts portal and found all sorts of definitely different valve but one 'spares kit' that looker remarkably close to the one I'd dismantled. Listed as a spare for a totally different machine and NOT for a 3CX I got a spares dealer to measure the bits and guess what - the same size :ddb:
Armed with the part number I was then able to identify the correct O ring and backing ring and ordered a complete 'spares kit' ie the whole check valve, and also spare O ring and backing washer. These arrived this morning allowing me to replace the complete check valve in situ on the machine and have bits to repair my original auxiliary valve as a 'shelf spare' for the future.
Although far easier than removing the auxiliary valve for bench repair replacing the check valve while on the machine wasn't the easiest task however it is done and works so far without any leaks ! I've still to repair the spare unit.
Sea.dog:
I'm surprised that a dealer wasn't aware that the 3CX was used on later models. It used to be common place in the automotive and motorcycle worlds for dealers to know interchangeable parts.
vtsteam:
One of the things we Madmodders do, which is unusual elsewhere, is investigative research beyond the usual authoritative answers. It's always fun to read about one of us succeeding where most people give up: No Longer Available.
Say's who? :dremel:
We're not friends of planned obsolescence.....
awemawson:
Thanks Steve. Yes also 'beyond economic repair' is another of my red flags.
If I'd have known it was as simple as it is I'd have pulled the original auxiliary valve apart and even if I had to make the backing ring I'm sure the odd size O ring could have been sourced. That way I'd have saved a sizable chunk of hard won cash (the 'good used' item was £250 including VAT and carriage)
I've just rebuilt the original valve as a known good shelf spare - to my surprise I find the backing ring is actually split with a 45 degree overlapping cut making fitting to the valve body very easy. I'd expected to have to warm it in hot water, and indeed was advised to do this by the dealer, but that wasn't necessary.
The split backing ring shows up on this image from a CAT dealer's parts site !
PekkaNF:
I enjoy much these stories.
--- Quote from: awemawson on May 30, 2022, 11:04:17 AM ---....
I've just rebuilt the original valve as a known good shelf spare - to my surprise I find the backing ring is actually split with a 45 degree overlapping cut making fitting to the valve body very easy. I'd expected to have to warm it in hot water, and indeed was advised to do this by the dealer, but that wasn't necessary.
The split backing ring shows up on this image from a CAT dealer's parts site !
--- End quote ---
Looong time ago I needed to field fit one of that kind of hard plastic backing ring on a hydraulic valve. There was no professionals, but there was a spare part and me...I got a hand-written instructions from the office (fax). I had to ask machinist to make two cones, one to expand the seal and the other to calibrate (shrink) the expanded backing ring. Third one was just a piece of pipe to push the seal straight. The backing ring needed to be heated in oil to about 70-80 C and then it would be pliable enough to stretch. That ring was pretty hard, felt like POM hard.
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