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miketomcat

Brake Shuttle valve

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Does anyone know what thread the plastic switch is that screws into the bottom of the shuttle valve. Its the valve thats fitted on the bulkhead of early 110s. Mines weeping but the switch is no longer used so was thinking some sort of bung. Especially when the valve is around £200 :blink:.

Mike

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I know it's not quite the question answered but if the switch isn't used, isn't the shuttle valve pointless? I thought it was to detect a pressure difference Ie a leak in one circuit. If it's in't doing any detecting you could replace possibly replace it with a couple of joins or blank the feeds off. 

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It also blanks off the leaking side so you don't just pump fluid on the floor. I can switch to a 300tdi master cylinder and delete the valve but I'm trying to avoid that for now.

Mike

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Confuse yourself silly with this thread?

Looks like the same part AAU1700 on Series3, so 3/8 UNF sounds plausible, you might even be able to put a bleed nipple in there?

(Never looked at one myself, so could be wildly off here!)

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mike. my 110 had that valve and i had brake problems so i took it out and made 2 small link pipes. 

may have it somewhere still  

there is no need to change to a 300 master as 

1) its only a pressure differentiate indicator

2) you still got 2 circuits off the master so if 1 fails you still have 1 brake circuit. 

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If it's like those on SIIIs, it doesn't shut off the leaking side - the PDWA unit on SIIIs is purely a warning system, made redundant by the far more effective level sensing caps of later vehicles.  If that is true of the Defender unit, then you'd be better off bypassing it - they tend to seize in place anyway and make bleeding far more of a chore.

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The only thing that concerns me about bypassing it is the 300tdi master has 3 ports and no shuttle valve. We're as the pre 300 has 2 ports and a shuttle valve. There must be a reason for this. I'm sure I read some where it closes the leaking side but maybe wrong.

Mike

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PDWA does shut off the leaking side, my '89 110 has its PDWA still, never given me any problems when bleeding the brakes

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20 hours ago, miketomcat said:

The only thing that concerns me about bypassing it is the 300tdi master has 3 ports and no shuttle valve. We're as the pre 300 has 2 ports and a shuttle valve. There must be a reason for this. I'm sure I read some where it closes the leaking side but maybe wrong.

Mike

the older 110 split front to rear on master cylinder. 

the 3 port splits front and rear on 1 part of the master and the other front out the other port. so they must think its safer to run just 1 front rather than just rears in case of major leak which i can see the sense in that logic. 

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i have my old valve with switch if you want it. just cover postage cost

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21 hours ago, miketomcat said:

The only thing that concerns me about bypassing it is the 300tdi master has 3 ports and no shuttle valve. We're as the pre 300 has 2 ports and a shuttle valve. There must be a reason for this. I'm sure I read some where it closes the leaking side but maybe wrong.

Mike

If using a PDWA unit, you wouldn't want to split left and right until after the unit - it can only deal with two circuits.  Once deleted, the master cylinder became the easy point to split the front system left and right.  A Tee could have been used nearer the front axle, I suppose, much like the rear or on the front of Series vehicles, but I'd be guessing at why it wasn't.

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the earlier master 2 pipes goto the pdwa. from there 1 line does both rears, the other both fronts with a t by o/s/f spring seat in chassis. 

only way to split left/right or diagonal is to have 2 lines to the rear. 

the earlier master also has a bigger union on 1 port so i assume 1 stage of master creates more fluid movement. 

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