AlanT Posted July 25, 2021 Report Share Posted July 25, 2021 Morning Experts, do you know if rebuild kits are available for these? I’m in the final stages of returning a car from 20 years of dereliction. All other brake parts are new but a new one of these is another £200 I’m keen to avoid. thanks Alan Link to comment Share on other sites More sharing options...
KevinR Posted July 25, 2021 Report Share Posted July 25, 2021 Google “PDWA rebuild kit” and you will find lots of options Link to comment Share on other sites More sharing options...
Pete Lewis Posted July 25, 2021 Report Share Posted July 25, 2021 there are two sizes of pdwa valves the stag kit is cheapest but didnt fit the valve off the spitty even tho they are often listed as the same base valve part number realy you only need the small 0 rings there is nothing expensive in these valves a small shuttle piston with 0 rings on eg https://www.jamespaddock.co.uk/brake-bias-valve-pdwa-kit-2 nothing to stop you strip and clean what you have and examine seals for wear Pete Link to comment Share on other sites More sharing options...
AlanT Posted July 26, 2021 Author Report Share Posted July 26, 2021 Thanks. I've now taken apart and it does look clean enough to rebuild. Will get some seals and give it a go. A Link to comment Share on other sites More sharing options...
Pete Lewis Posted July 26, 2021 Report Share Posted July 26, 2021 considering there is sod all insde why the price hikes doesnt make much sense other than rip off two 0 rings and crappy switch most are old and seized so knowone knows iif it would work or not I had a spitty to fix lost all rear fluid and the switch had been disconnected probably for years was a hammer it out to repair its idea is any line failure the piston pops across lights the warning and closes the leaked line off so no more leakage well 45 years ago they were good , and in reality you could remove the piston , who would know , the warning lamp would still have a bulb test from the low oil pressure switch thats all a MOT can test for this looses the split line braking but if the valve has stuck you may only have single line and be totally unaware one end of the car has been shut off for ages till the dyno says theres a low efficiency somewhere pete Link to comment Share on other sites More sharing options...
rlubikey Posted July 28, 2021 Report Share Posted July 28, 2021 Alan, you will feel the pressure differential with your foot (brake pedal sinks further), along with the Spit not loosing speed as quickly as expected! A Posteriori. Far better to put a low fluid switch cap on the master cylinder and wire that to the dash warning light. Cheers, Richard Link to comment Share on other sites More sharing options...
DVD3500 Posted July 28, 2021 Report Share Posted July 28, 2021 31 minutes ago, rlubikey said: low fluid switch cap What's that? Link to comment Share on other sites More sharing options...
Pete Lewis Posted July 28, 2021 Report Share Posted July 28, 2021 like this the reservoir cap has a simple float which as the level drops it completes a circuit to a warning lamp available from the many but needs the right one to fit the top of your master cyl reservoir https://www.carbuilder.com/uk/brake-fluid-reservoir-cap-with-2-pin-plug-and-fly-leads 1 Link to comment Share on other sites More sharing options...
rlubikey Posted July 28, 2021 Report Share Posted July 28, 2021 DVD3500, it's a master cylinder cap with a float switch built in. The fluid level drops and the switch is activated. If it's a slow leak it gives you advanced warning. I see Car Builder Solutions have a switch you fit in your existing cap (drill a hole). Or there are period metal caps with switches such as fitted to Rovers. Cheers, Richard 1 Link to comment Share on other sites More sharing options...
Pete Lewis Posted July 28, 2021 Report Share Posted July 28, 2021 Ha ha Richard Snap !!! Pete 1 Link to comment Share on other sites More sharing options...
DVD3500 Posted July 28, 2021 Report Share Posted July 28, 2021 Right.... The 1500 I hope to pick up soon has a PWDA I was planning on just eliminating it... I figured the lack of braking was as good an indicator as anything... I doubt those caps work on tandem systems...? Or do they? Link to comment Share on other sites More sharing options...
Pete Lewis Posted July 28, 2021 Report Share Posted July 28, 2021 that all depends on the access to the reservoir on a tandem master if you remove it and the MOT man knows his stuff that would fail... Where;s you valve mate ??? keep it fitted but without any inards and knowone knows pete Link to comment Share on other sites More sharing options...
DVD3500 Posted July 28, 2021 Report Share Posted July 28, 2021 1 hour ago, Pete Lewis said: keep it fitted but without any inards and knowone knows Ah... did not know that was an option. 😉 Well I am likely going to have to go for a "prototype" approval for my Spitfire. As I mentioned before I have making one car out of 2 and since a lot of the car is from a US car I might as well build the car I want and get approval rather than getting "exceptions" for everything that is not "original" or "standard". The German MOT aka TÜV basically allows 3 permission types: 1. H for Historical: The car most be original or "in period" or EVERYTHING down to the radio. Pain to achieve but has allows for cheaper insurance and let's you drive where there are smog restrictions. 2. "Regular" Permission. Easier to achieve but anything that is not standard gets scrutinized and must be added to paper work (at a cost usually). Changed even to the size of tire or wheel are technically not allowed and Higher Power forbid you make "upgrades" like stainless steel brake lines. 3 "Prototype" literally "one-time" approval. Expensive (I have read from 60 to 600€), but essentially the car gets a once over and if you can convince the engineer it is road worthy he allows it. The best way is to get the engineer on board BEFORE making the changes and then he lets you know if he will allow it before you put it on. Given I am taking the best out of a MKIV (looks) and 1500 (US doors, rear bumper etc.) I reckon this is easiest... I wasn't planning on anything too crazy for the Spitfire brakes. I just wanted tandem and I don't want a dummy light on the dash. I don't think I need GT6 brakes or anything crazy like that. Mark Field set me up with some nice pads and shoes (that he forgot to send me in December ! 😄 ) and I think I will be fine. Great tip about hollowing out the PDWA though! Link to comment Share on other sites More sharing options...
rlubikey Posted July 29, 2021 Report Share Posted July 29, 2021 On 28/07/2021 at 16:58, DVD3500 said: Great tip about hollowing out the PDWA though! Not completely hollow it out, or that would connect the dual circuits and negate the safety of the system! ** I would leave everything in place but, if the PDWA gave problems, add the special cap to the master cylinder. Then you disconnect the wire somewhere it won't be noticed (or maybe you declare it to the Prototype Inspector and hope he understands) and connect the dash light wire to the cap switch instead. Cheers, Richard ** I had the dual circuit braking grafted on to my '77 Spit when it was converted to six cylinders. Unseen by me or the MOT chap a brake pipe was rubbing against the armoured PI fuel hose. Some years later the brake pipe burst while braking for a roundabout. This is how I know that the PWDA is useless when you get a catastrophic failure. You don't spend any time at all looking at the dash wondering why the light has come on. You immediately feel the brake pedal is different and so is the car's ability to loose speed. Anyway, I was jolly glad of the dual circuit system that day. Not sure I could have stopped on the handbrake in time. 1 Link to comment Share on other sites More sharing options...
Pete Lewis Posted July 29, 2021 Report Share Posted July 29, 2021 removing the inner shuttle piston is a "on your own "fix , making it back to single line is better than having the valve shut one circuit off and you dont know dont know why these simple valves cost silly money everyone trys to rebuild a master cyl and wheel cyls but jib at the PWDA i dont advocate a bodge but something that works is an advantage over something that doesnt is twin line that good triumph dumped it on the last 2000 saloons ...cost driven pete Link to comment Share on other sites More sharing options...
PeteH Posted July 29, 2021 Report Share Posted July 29, 2021 Interesting thing about Dual circuit systems, some are split front/rear and some are diagonal split?. Advantage of one or the other?. My first thought, is that the maximum braking effort is best on the front wheels? But with a diagonal split IF the front circuit is the one that fails, at least one front wheel is being braked.? Pete. Link to comment Share on other sites More sharing options...
SpitFire6 Posted July 29, 2021 Report Share Posted July 29, 2021 On 26/07/2021 at 13:20, Pete Lewis said: SNIP******r its idea is any line failure the piston pops across lights the warning and closes the leaked line off so no more leakage SNIP******** Hi Pete, My understanding of the PDWA is different. The PDWA activates a contact & that is it. It's a Warning Actuator only. Cheers, Iain. Link to comment Share on other sites More sharing options...
DVD3500 Posted July 30, 2021 Report Share Posted July 30, 2021 Thanks! I will let you all know what we do in the end... 😉 Link to comment Share on other sites More sharing options...
Pete Lewis Posted July 30, 2021 Report Share Posted July 30, 2021 11 hours ago, SpitFire6 said: It's a Warning Actuator only no the shuttle should close off the pressure lost line as its moved across by the pressure difference to arrest any more fluid loss Pete Link to comment Share on other sites More sharing options...
AlanT Posted July 31, 2021 Author Report Share Posted July 31, 2021 Well the seals have arrived and will see if they fit… Link to comment Share on other sites More sharing options...
AlanT Posted July 31, 2021 Author Report Share Posted July 31, 2021 Sizes no good on from James Paddock I’m afraid - the original is much bigger. About 14mm diameter. The piston only had one seal on it but two circlips. I guess one had disintegrated. Any idea where I might find the seals? Leaving the piston out would put the warning light on since a metal sleeve sits around the piston and inside the seal and circlips and keeps the switch depressed. thanks Alan Link to comment Share on other sites More sharing options...
Colin Lindsay Posted July 31, 2021 Report Share Posted July 31, 2021 http://www.zen11896.zen.co.uk/vixen/parts/pdwa.html https://static1.squarespace.com/static/5c6dec53b10f25d4edf0b3f7/t/5d019238b9af3e000109c65f/1560384058350/Overhauling+Master+Cylinder+%26+PDWA.pdf Two articles that may be of use. The first claims that there are two different sizes for the Spitfire; could this be the problem with the Paddock kit? Link to comment Share on other sites More sharing options...
AlanT Posted July 31, 2021 Author Report Share Posted July 31, 2021 Thanks Colin. mine’s the later one so may need to go to a specialist supplier to get the seals. Alan Link to comment Share on other sites More sharing options...
AlanT Posted July 31, 2021 Author Report Share Posted July 31, 2021 The diagram also suggests the 2nd sleeve is still stuck in the housing Since I’ve only one come out so not to fiddle with Link to comment Share on other sites More sharing options...
AlanT Posted July 31, 2021 Author Report Share Posted July 31, 2021 Now fully disassembled with second seal and sleeve out. Link to comment Share on other sites More sharing options...
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