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Rebuilding The Brake Limiter Valve


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#1 Carlos W

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Posted 29 February 2016 - 12:19 PM

Can you rebuild the brake limiter valve?

 

The one I've got has been in a box for several years, I got it with a job lot of spares. Someone has gone to the effort of plugging the holes for the pipes so it's been sealed against dirt.

 

Is there any way of rebuilding them? 

 

Is it likely to be faulty, and if it is will I be able to tell when I try and bleed the brakes?

 

A new one is 80 quid, and I thought I'd seen a thread where someone rebuilt one but I can't find it



#2 nicklouse

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Posted 29 February 2016 - 12:52 PM

are you on about the one on the rear subframe? one hole in and two out?



#3 Itsaminithing

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Posted 29 February 2016 - 12:56 PM

Are you talking about the early rear subframe mounted brake limiter valve or the later 1978on bulkhead mounted dual line pressure reducing valve?

It's easy enough to take the later one apart (though you will probably destroy the end cap & will need to find some way of replacing it) - the difficulty is finding the correct replacement internal seal - something similar just won't do!

In theory anything is possible but the question you have to ask yourself is.... Is it worth risking the life of you/your family/other people for the sake of £80?



#4 Carlos W

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    Mine is purple, but I have been told that's normal

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Posted 29 February 2016 - 01:02 PM

It's the later one on the bulkhead.

 

If there's an internal rubber seal in it, then any corrosion in the bore is going to eat the seal when I start using it.

 

Looks like I'll be adding a new one to the shopping list 



#5 slidehammer

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Posted 29 February 2016 - 01:48 PM

I don't think you be able to get the internal components to do it anyway. Buy new for piece of mind.



#6 Carlos W

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    Mine is purple, but I have been told that's normal

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Posted 29 February 2016 - 01:50 PM

I don't think you be able to get the internal components to do it anyway. Buy new for piece of mind.

 

Ah well I suppose with TMF+ discount I'll save more than the fiver subscription on this purchase alone



#7 Itsaminithing

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Posted 29 February 2016 - 02:43 PM

In the case of a suspect '78 on brake pressure reducing valve it is possible to check whether it's working or not -if only to rule it out when you have to identify an untraceable braking issue.
(Unit needs to be removed it from the car) Try to move the piston in the bore slightly (not easy due to the spring pressure) -if you can't then bin it!
Use a bicycle pump (or something similar) pump air into one half of the piston whilst blocking off the corresponding bottom hole, If air escapes from the other side of the unit the seal is shot - once again bin it!
(I never save money on brakes, tyres or steering/suspension components -one day my life might depend on them).
 

Edited by FlyingScot, 01 March 2016 - 08:45 AM.
Unnecessary smutty remark deleted


#8 Carlos W

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    Mine is purple, but I have been told that's normal

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Posted 29 February 2016 - 02:53 PM

I think with the time it's stood I'll buy a new one. 



#9 Itsaminithing

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Posted 29 February 2016 - 06:08 PM

Wise choice.... Can you buy two as i need one!

(I would only test a unit if it was on a car & the brake bias started going wrong).



#10 Spider

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Posted 29 February 2016 - 06:52 PM

They only have 4 x O rings in them and a few people have re-built them, though it's in 'the balance' as to whether they were intended to be rebuilt.

 

One end has a cap that's been crimped, you need to pry the crimping back out and then remove the cap, under that is a spring and a piston. The other end has the hex plug which will allow access. CAUTION: there is a small square bar inside there, which sits on top of the piston at this end and is right under the plug, very easily lost or over looked.

 

There's two separate pistons inside, and they come out each end. There's also a shuttle inside which is retained by a M5 nut and then the inner assembly is screwed together, can be dismantled once it's out.

 

IMO, they are a crap idea and a very fiddly thing to rebuild.

 

Tip: there is no reason why the very early type of shut off valve can't be fitted, with an appropriate pressure setting. Originally, these were fitted to the rear subframe, however, they can be fitted anywhere in the rear circuit, even adjacent to the Master Cylinder.



#11 Carlos W

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Posted 29 February 2016 - 07:30 PM

Update, there's evidence of rust in the threads of it. 

 

I'll buy binning it and buying a new one



#12 Itsaminithing

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Posted 01 March 2016 - 08:42 AM

They only have 4 x O rings in them and a few people have re-built them, though it's in 'the balance' as to whether they were intended to be rebuilt....

IMO, they are a crap idea and a very fiddly thing to rebuild.

So i'm not the only one to be mad enough to strip one down.

Couldn't find a replacement for the double-lip O ring that sits between the two chambers so i gave it up as a bad idea.

Life's just too short for stuffing mushrooms.... or rebuilding pressure reducing valves.



#13 Carlos W

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Posted 01 March 2016 - 08:48 AM

They only have 4 x O rings in them and a few people have re-built them, though it's in 'the balance' as to whether they were intended to be rebuilt....
IMO, they are a crap idea and a very fiddly thing to rebuild.

So i'm not the only one to be mad enough to strip one down.
Couldn't find a replacement for the double-lip O ring that sits between the two chambers so i gave it up as a bad idea.
Life's just too short for stuffing mushrooms.... or rebuilding pressure reducing valves.

what about stuffing peppers?

Opinion appear unanimous I'll be replacing

#14 dklawson

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Posted 01 March 2016 - 12:54 PM

Couldn't find a replacement for the double-lip O ring that sits between the two chambers so i gave it up as a bad idea.

 

 

I have never seen these valves.  Is there any chance you have a picture of them taken apart and showing the seal?



#15 Itsaminithing

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Posted 01 March 2016 - 01:38 PM

Ooops....  NO, it got binned.

Over a year since i took it apart, tried asking a friend whose heavily into different British Classics of that era if he knew of or could find the correct seal without any luck.

Maybe worth sending Moke Spider a message to see if he can help.






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