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PDWA

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PDWA
#1
CaptainG Garry Needham
Omond Beach, FL, USA   USA
HI all. I just purchased a 1980 Spitfire to restore. Most of the body work and paint has already been done. Starting to work on the brakes. I have decided to replace both master cylinders rather than rebuild. My concern is how do you know if this PDWA thing is working before you reinstall everything. I have rebuilt MGA"s so this is my first encounter with this component.

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Falkon Avatar
Falkon Al Martin
Appleton, WI, USA   USA


Attachments:
6-94246-popcorn-1424810325.jpg    58 KB
6-94246-popcorn-1424810325.jpg

Doug in Vegas Avatar
Doug in Vegas Douglas D
Las Vegas, NV, USA   USA
The internal shuttle needs to be held still while bleeding.

The PDWA should not leak.

That's about it. It's considered to be and obsolete component that's more trouble than it's worth that many of us have ditched.

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Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
I guess you could manually pull the switch and work it. But that would not tell you if the shuttle valve is stuck, or will leak on you.

I suggest you do a search here on PDWA's

CaptainG Garry Needham
Omond Beach, FL, USA   USA
Thanks for the info. If you ditch it as stated do you just install as is, as long as no leaks and disconnect the switch?

DerbyRam54 Neville Wardle
Branford, CT, USA   USA
As Tony said, a lot of threads on here about this little gem. We go through a lot of popcorn on this one, almost worthy of a sub-forum.

A quick synopsis:

Disconnecting the switch still leaves you vulnerable to a leak at the switch if the internal seals are shot.

The seals on the PDWA fitted to a 1980 are not available although an article on the VTR site reckons to have the spec for a substitute: https://vintagetriumphregister.org/pdwa/ The same text with the drawings that for some reason aren't on the VTR site is at http://www.zen11896.zen.co.uk/vixen/parts/pdwa.html

It's probably a moot point though because the single-ended one is unlikely at this stage to come apart very easily. It almost looks like it wasn't intended to be serviced. The problem I encountered is that the sleeves are well and truly stuck, I got the near one out but the far one won't budge and the seal is beyond that and so can't be replaced. Whoever designed that deserves a foot up their ar$e.

Removing it will leave you with a gap in the brake lines. Some have suggested using unions to bridge that gap. Be aware the lines have a curious mix of fittings, ostensibly to stop you getting the lines mixed up.

There have been suggestions of plugging the bore between the two ports, though this leaves you back with the issue of disassembling the unit to modify it.

The earlier unit is available at a cost, but would require you to change the brake lines because the fittings aren't the same.

If you don't want the PDWA at all the most straightforward approach would be to make up new brake lines to run from the master cylinder to the three way junction (front brakes) and to the union on the line to the back which is near the clutch slave cylinder. You can't buy made-up lines because of course they assume there is a PDWA.

For a device that really isn't much of a safety feature it causes more than its share of grief.

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
First class synopsis thumbs up

Falkon Avatar
Falkon Al Martin
Appleton, WI, USA   USA
Darn it Tony. Now I had to go and look up synopsis.

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
In reply to # 1594789 by Falkon Darn it Tony. Now I had to go and look up synopsis.

Don't feel bad, until Neville used the word in context, I thought it was a STD ;-)

Re: PDWA
#10
Falkon Avatar
Falkon Al Martin
Appleton, WI, USA   USA
At least I need not worry of becoming sesquipedalian.

Re: PDWA
#11
65or66 Jim B
Lake village, IN, USA   USA
1965 Triumph Spitfire MkII
1971 Triumph Stag
1973 Triumph Spitfire 1500 "Jusanudda Munny Pit"
All right y'all, this is a kid-friendly site. No more of that dirty talkgrinning smiley

Re: PDWA
#12
DerbyRam54 Neville Wardle
Branford, CT, USA   USA
I agree. This PDWA sounds like a very shady organization. What does it stand for? Perverts Doing Weird Acts?

Re: PDWA
#13
spitfire50 Avatar
spitfire50 Paul Mugford
Rochester, N.H., USA   USA
In reply to # 1594824 by DerbyRam54 I agree. This PDWA sounds like a very shady organization. What does it stand for? Perverts Doing Weird Acts?

Neville,
Well lets just say it isn'r Pretty Darn Wonderfully Amazing winking smiley
All the best,
Paul

Re: PDWA
#14
Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
I am pretty sure the PDWA was designed by the same idiot that came up with the Big Lid master cyl.
Why on earth with that huge lid did they make it so difficult to get fluid into the rear compartment?

Also brake fluid absorbs moisture from the air, so the Big Lid provides the most exposure possible.confused smiley

Got to have been the chaiman's idiot nephew in the drawing office.

Re: PDWA
#15
DerbyRam54 Neville Wardle
Branford, CT, USA   USA
In reply to # 1594950 by spitfire50
In reply to # 1594824 by DerbyRam54 I agree. This PDWA sounds like a very shady organization. What does it stand for? Perverts Doing Weird Acts?

Neville,
Well lets just say it isn'r Pretty Darn Wonderfully Amazing winking smiley
All the best,
Paul

Part Didn't Work Anyway

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