Hey - did you know if you click on the title of a thread it will take you to the first unread post since you last visited that thread?
but were afraid to ask: 
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smilie in place of the real @
Pretty Please - add it to our Events forum(s) and add to the calendar! >> 
I recently took my valve apart and it looks like it would do more than just activate the light, when it moves to one end or the other it looks like it partially blocks off what ever ciruit it moves toward.If you are having problems with the valve or to avoid problems why not remove the piston and then you wouldnt have to worry about the valve causing unbalanced braking? When your bleeding the brakes isnt that the same as having a leak causing the valve to at least partially shut down what ever circuit you are bleeding--possibly making it harder to bleed??? I really dont know for sure just asking and trying to figure it out like everybody else.
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I can't answer the question about blocking off the side with lower pressure, but it certainly has to be re-centered using a nail or long scribe/probe after brake bleeding. PITA.
And while I still think it's a nifty little device, I have to admit that when it sprung a leak, it took off most of the paint on the frame member it sits on. Hard area to touch up.
And while I still think it's a nifty little device, I have to admit that when it sprung a leak, it took off most of the paint on the frame member it sits on. Hard area to touch up.
Scott_Hower
Luke Skywalker
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Ok, I have to admit that I have no experience with Triumph PDWAs, but I have plenty with those in MGs. /bcforum/images/%%GRAEMLIN_URL%%/smile.gif
The design is similar, if not identical. Here is a photo of the shuttle inside an MGB PDWA. It has square cut grooves for the fluid channel seals (removed). These most certainly will seal one side from the other in the event of a leak/failure/whatever you call it.
I originally stated it keeps the two circuits of a tandem MC seperate and I respectfully stand by that statement. No one will convince me otherwise.
I'll go back to the MG forum now, sorry for lurking here /bcforum/images/%%GRAEMLIN_URL%%/smile.gif
The design is similar, if not identical. Here is a photo of the shuttle inside an MGB PDWA. It has square cut grooves for the fluid channel seals (removed). These most certainly will seal one side from the other in the event of a leak/failure/whatever you call it.
I originally stated it keeps the two circuits of a tandem MC seperate and I respectfully stand by that statement. No one will convince me otherwise.
I'll go back to the MG forum now, sorry for lurking here /bcforum/images/%%GRAEMLIN_URL%%/smile.gif
swift6
Yoda
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Scott_Hower said:
Don't run off Scott, nothing wrong with what your saying. That photo does match the Triumph PDWAs that I have had apart. Your right that the seals/o-rings do keep the front and rear brakes separate. The only time it doesn't is if both o-rings fail at the same time. Which hopefully would be on the very rare occasion.
When the shuttle slides from lowered pressure on one side, it doesn't block flow on the side showing lower pressure. A little bit of pressure to brakes when needed is still better than no brakes.
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FWIW, following up on my prior point about the TR-250 having a slightly different PDWA shuttle than the TR-6, here's a photo that shows the two different kinds. Not entire relevant, but perhaps helpful for the 250 owners out there. The seal kits only work with the TR6 shuttle, so I found one from a later car. The PDWA brass housing is identical for both cars.
Best,
Bill S.
Best,
Bill S.
bobh
Jedi Warrior
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Scott and Bill,
Good pictures. The later shuttle valve design was a big improvement over the original. The manuals illustrate the older style.
As for sealing a lot depends on the internal configuration of the body and the amount of travel for the shuttle valve.
In the interest of science and the Eternal Brotherhood of British Car Owners I'll volunteer to get a PDWA body sectioned and provide photos of the cut away assembly if someone will supply an old PDWA assembly.
Based on the similarities in the photos the shuttles appear to be nearly identical. It's likely that either an MG or Triumph assembly will allow us to see the function. Being a Triumph owner I would prefer a Triumph unit, but will accept either.
PM me if you have an old unit to sacrifice.
BOBH
Good pictures. The later shuttle valve design was a big improvement over the original. The manuals illustrate the older style.
As for sealing a lot depends on the internal configuration of the body and the amount of travel for the shuttle valve.
In the interest of science and the Eternal Brotherhood of British Car Owners I'll volunteer to get a PDWA body sectioned and provide photos of the cut away assembly if someone will supply an old PDWA assembly.
Based on the similarities in the photos the shuttles appear to be nearly identical. It's likely that either an MG or Triumph assembly will allow us to see the function. Being a Triumph owner I would prefer a Triumph unit, but will accept either.
PM me if you have an old unit to sacrifice.
BOBH
Scott_Hower
Luke Skywalker
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bobh said:
PM sent.