18 replies to this topic

[lindsay_palmer]

Can anyone post a picture of a PWDA Valve or exploded diagram? I have one to put back together and lost the photo I took of how it all goes together.

 

Also, does anyone do kits for these? 

[lrostoke]

If its the valve on the bulkhead with the 4 connections this is the warning in Haynes concerning it

 

 

4 The pressure reducing valve is a sealed unit

and cannot be dismantled. If the valve is faulty

it must be renewed as a complete assembly.

 

So probably going struggle get a diagram or a kit.

Edited by lrostoke, 17 December 2013 - 01:30 PM.

[Dan]

  It's NOT a PDWA, and no there are no service parts available.  As above it's meant to be replaced as a unit.  If you search the dark recesses of this forum you will find a thread where one of us stripped one of these down and cut it up to see about the possibility of servicing them.  If you can find it that might help you get it back together but I think either the whole thread or at least the photos are likely to have been eaten by a major server crash we had a few years back.

[Steve8274]

What year where these fitted on? My car (1986) doesn't have one but someone recently who came to look at doing some repairs on it said it should have one. At the moment the pipes are connected together with brake pipe nuts where this valve should be.
If required, anyone got a spare because they expensive to buy new? Repair guy said maybe this the reason it not been replaced. I only acquired car in june and it not been on road yet.
Sorry if this appears to hijack thread. Not meant to but because pictures up of it thought it would be ideal place to ask
Steve

[Dan]

  They were fitted from '78 to the end of production.  Yes they are expensive but get a new one, second hand ones are not really reliable unless they are very new indeed and nobody is crashing new Minis much these days.  Your car must have had something done to reduce the rear line pressure otherwise it would have killed you the first time you drove it, believe me they swap ends very easily when this valve is faulty or deleted.  Check that some other form of rear pressure control hasn't been fitted before you install one.

[Steve8274]

  They were fitted from '78 to the end of production.  Yes they are expensive but get a new one, second hand ones are not really reliable unless they are very new indeed and nobody is crashing new Minis much these days.  Your car must have had something done to reduce the rear line pressure otherwise it would have killed you the first time you drove it, believe me they swap ends very easily when this valve is faulty or deleted.  Check that some other form of rear pressure control hasn't been fitted before you install one.

Thanks for the response. The car hasn't been drove by me yet. It had been in a garage for few years before I purchased it and i trailered it home. The drivers rear brake was locked on. Not sure if this was because of lack of use or because of this valve. Can't see any other pressure valves so looks like I need one.

[lrostoke]

The pressure valve maybe underneath on the rear subframe if they managed get an earlier model type

[Steve8274]

Ok thanks. Will have another look. Did check the lines quickly but didn't give a thorough check.
If one is on there, is this acceptable or should I replace with one in bulkhead?

[Ethel]

There was a brief period where they didn't have any valve. Thet had a diagonal split system instead with smaller rear wheel cylinders. I think they'd also have a proper PDWA built into the Master cylinder - that's pressure differential warning actuator, with an electrical connection for the warning bit.

 

You can get a nice adjustable wilwood valve similar to the FAM7821 http://www.rallydesi...oducts_id=15436

 

...just noticed your car's date, it should defo have the FAM valve, You can track down the fault by bleeding off the pressure along the line - obvs only bleeding between the blockage and wheels can release them, that's if it's even hydraulics. My first suspicion would be the linings themselves, then the handbrake linkage.

[ado15]

If it's only one rear brake, it will be related to that corner of the car, not the master or (lack of!) valve.

 

Check the handbrake is releasing correctly on that side. The quadrant can seize.

Or the hydraulic cylinder could be seized.

[lindsay_palmer]

Thanks for all the information.

From what I've read this valve causes all kinds of problems.

I think I will buy the wilwood valve suggested by Ethel.

How do people get the adjustment right on the adjustable valve?

I have the spare early type valves for under the boot floor. Can I use one of these instead?

[Dan]

  The valves don't cause trouble really, not until they fail but that's like anything.  People remove them because they don't understand them, they were fitted to loads of models for many years.  It should be noted that adjustable bias is not legal on a road car, if you fit an adjustable valve you must at least fit it so you can't reach the control from the driver's seat but that still isn't strictly allowed.

[Steve8274]

Great info. Thanks for the help. Few more jobs to add to my never ending list

[lindsay_palmer]

Thanks. This is for a road car so adjustable is out of the question.

Can I use the pressure valve normally mounted to the rear subframe?

[cal844]

you can fit an adjustible valve, IT MUST NOT be reachable or controlled from the cabin. also for it to be legal for road use it must be welded once the pressure has been set.