• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

PDWA rebuild

Share this page

sparkydave

sparkydave

Jedi Knight
Country flag
Offline
It seems my PDWA finally let go in a big way. Front half of the master cylinder went bone dry after sitting for a week, and unscrewing the switch I see a suspicious amount of brake fluid behind it. Seems to me I attempted to get it apart a long time ago, but gave up trying to get the plug off the end since it didn't appear to be leaking. Anybody have suggestions on how to unscrew that thing? Mine is actually the brass PDWA.
 
Assuming you have already taken the unit out of the car, hold the PDWA body in a vise after wrapping it in cloth or sandwiching it between thin boards to prevent damage. Use a box end wrench and strike the other end with a hammer. It should spin out w/o too much trouble.

The Buckeye Triumph site has/had information on rebuilding PDWAs. You will also find information on Paul Rego's web site (Brosky from the Triumph forum here) https://www.74tr6.com/ Look for the PDWA link at the very bottom of the page.
 
Looking at how that's gripped in the vise it looks a little scary, but I'll give it a try. Thanks much Doug!
 
I agree that serrated vice jaws against tapped holes does not look comforting. I don't open these the way that Paul shows. Instead I place a paint stir stick on each side of a leg for the "H" profile of the PDWA and squeeze that sandwich in the vice. The stir sticks are ruined when I am done but the surface of the PDWA is protected.
 
Success! Since the seals were already shot I figured I'll take my chances with the PB Blaster and propane torch. A couple hours of soaking with some Blaster, some liberal heat with the torch, a few taps on the end of the 18" breaker bar with the hammer, and it popped right off. I found what worked even better than the paint sticks to protect the brass was some scrap aluminum I had lying around. I cut a couple strips to put between the vise jaws and the body, and not a scratch. The only thing that has me a little concerned is the copper washer that came in the rebuild kit is smaller in diameter than the old one. Can the old one be re-used?
 
After annealing the washer, sand it flat by rubbing both sides across piece of wet/dry paper placed on top of a piece of plate glass.

You found a rebuild kit? WHERE? Inquiring minds really want to know!
 
Moss has them, part number 181-995 is listed for a Spridget. Not sure why the washer that came in mine is smaller, but I bought it a few years ago. Thanks for the annealing tip, I'll give that a shot.
 
Son of a gun! It would have been nice to know that was available!

Of course, Moss' description as "Repair Kit" (without mentioning PDWA) doesn't make it easy to search for. The price is right also. Thanks for providing the part number!
 
No problem! I got to eyeball a buddy's '75 Midget today that needed some electrical help, and my PDWA looks different from his even though his is also brass. The hex end juts out about an inch, but his (and the Moss diagram) show a short, stubby hex end. Must explain why the washer doesn't fit.
 
As long as the internals are right I would be more than happy to have a rebuild kit with the correct parts. I have rebuilt 3 of these things but in each case I had to machine new pistons for inside so i could use standard size o-rings made of EPDM.
 
heh, you don't need to reinvent the wheel here guys...just google crushable washers or similar and you will find vendors that will have the right size at your door step as fast as a first class letter...
 
Sorry, I guess I was unclear.

I was not talking about making the crush washer. I was talking about making the piston inside the PDWA so it could use standard size o-ring seals. The copper washer can be re-used by annealing it and sanding it flat.
 
Woohoo! Works like a champ! Used the propane torch to heat the copper washer until it was red, sanded it after it was cool, and got it back together. The LBC gods must have been smiling on me; no leaks from the copper washer, no fluid oozing from the switch, and I got the brakes bled the first time. No leaks, and the brakes feel fine! (knock on wood):driving:
 
Back
Top