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Discussion Starter #1
Has anyone tried to use some kind of a sealer between the flat metal surfaces such as around the non-return valves and diaphragm?
Steel on steel is not a join I would use say on a water pump, never mind compressed air?
Thoughts? Suggestions?
 

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1995-2002 Range Rover P38A
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If the surfaces of the block pieces are nice and clean and you replace all the O-rings properly, there will not be any problems with how it seals and no need for any kind of additional sealant. I recall from when I rebuilt mine that everywhere there needs to be a seal there will be an o-ring. The only thing I can think of is the unlikely event that the metal blocks get warped somehow, but at that point you would really need to just replace it outright.
 

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yep, the metal-metal isn't the seal, it's the orings. The orings are thicker than the groove, so when you tighten it down to metal on metal, the oring is compressed and sealing quite well.

a little oring lube is a big help, each oring kit has a small packet included.
 

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Discussion Starter #4
Yes, thanks - what you both say makes perfect sense - going for my third rebuild and trying to ensure success at last.

In terms of lubricant, yes Dennis, thanks I used yours last time but have been reading about o-ring sealants and came across Dow 111 and Dow Molykote 55. The Dow 111 is a high quality o-ring sealant used by NASA apparently, while Dow Molykote is 55 is specifically for o-ring/metal interfaces and acts by slightly swelling the o-ring - I put some on an old valve block o-ring and it hasn't disintegrated it yet after a few weeks.
Any experience of these? Is it overkill? My valve-block has been leaking for about 15 months now so I am clutching at straws to ensure a perfect seal.

Thanks
 

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Dow makes excellent chemicals, I don't doubt them, but they may be a bit overkill (It's not rocket science :) ) By all means give it a try, I doubt it would hurt anything.


The lube I include is by Parker, the manufacturer of the orings I cary. As far as I know, most orings are metal-rubber seals. some seal to plastic, but most would be to metal.

With recurring leaks, your problems may be elsewhere, bad lines perhaps?
 

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Discussion Starter #6
Thanks Dennis, yes I know it is not rocket science (NASA! ha-ha! :)), the valve-block is a very simple thing really, much maligned by its antagonists but a mystery valve-block leak is totally baffling (it is not the airlines - I bought 50 feet of airline and ran new direct lines everywhere - made no difference whatsoever so I connected the original ones back).

The mysterious thing is that every time I rebuild it it leaks in a different place (or rather the pattern of collapse is different) which by deduction leads me to the conclusion that whatever I am doing with the valve-block is making it leak in a different place.

I always have different volumes of air leaking around the solenoid covers - it seems the o ring is not doing its job (could they be thicker?) either at the valve stem or the valve base. The stem solenoid is a 'moving' seal so there we are entirely at the mercy of the o-ring and its seat (an area where you say you have seen small cracks which I will inspect this time) but the valve base to metal seal is possible to 'enhance and assist'. The original valve stem seal is a vinyl sleeve which looks fragile to me and as if it would wear fairly rapidly - in your kit you replace it with an O-ring yet it is so small I wonder if anything could be done to help that seal?

However, the fact that the reservoir empties in several hours leads me to suspect that either the non-return valves are not sealing or the diaphragm is leaking (although the car pumps up readily which negates the diaphragm I think?) and those are the areas of 'leakage" I am most concerned in 'assisting'.

I mean if you think about a tyre or bicycle valve the principal is the same - the pressure of the air assists in making the seal on a rubber or vinyl seat, so why is it so difficult for me to make my valve-block stop leaking?
 
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