O rings (JCB valve block)

[Jack Russell]

We have a JCB 426 loading shovel. On top of the front axle is a large valve block that has a leak between the main block and a casting that has a relief valve in it. We have tried replacing the o rings a couple of times and the leak keeps coming back. Typically it’s a ridiculous amount for the o ring kits. Has anyone had much success making o rings up from the splicing kits? I can’t find one with the right section in any of our kits but have a piece in the splicing kit. Never quite trusted them for no real reason. Will be putting some schmoo (loctite gasket) in as well this time.
cheers
Will

 

[goldeneagle]

If you can size up what's required give a specialist manufacturer like https://www.jameswalker.biz/our-solutions/our-products/elastomers/o-rings a shout as they would have it in stock in a variety of materials. They may be able to advise on cause of failures experienced.However it could be as simple as a manufacturing error (o ring groove wrong size - not enough compression when loaded). The guidance is available here to check metal sizes and spec replacements https://www.jameswalker.biz/knowledge/resources/o-ring-product-guide

I believe some higher pressure hydraulic applications use a rubber with a harder shore hardness. The splicing kit section is normally a 70 shore hardness whilst a 90 shore hardness is used in some high pressure hydraulic applications.
Agree with the price from JCB as a maximum £2 o ring in a JCB bag is £20, yes they have to bag it and warehouse it if you want to justify it, it could however have a spec in service manual etc to allow suitable alternative to be procured.

 

[Blue.]

The splice kits are OK upto about 1psi

 

[dave7840]

If you know the size simply bearings will have what you need, they do 70 80 and 90 shore. But it bet the block has a crack in it if new seals dont help. Had two blocks crack on jcbs shovels in the last year only one in warranty. The lead time on a new block was 4 months but they had the slice that went instock for near the same money as a whole new block

 

[dave7840]

 

[Jack Russell]

Is there a dye you could put on to check for cracks? I’m sure I used a pour on dye in another application but can’t remember it’s name

 

[tomlad]

2 different aerosols usually.
crack detector
Not that ive used them personally
Will be loads of demo on utube

 

[Blue.]

Is there a dye you could put on to check for cracks? I’m sure I used a pour on dye in another application but can’t remember it’s name