which way does this mount??
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anyone ?

Don't go slow !!! Go Turbo :))))))

What is a fig 8 and a type 4??

My car ('79) has both the PDWA and the pressure reg on the rear subframe. I though the PDWA was just there to seal off one half of the system if there was a failure?

That valve is basically just a "failure conscious valve" (PDWA Valve)

It`s not a regulator,,, it`s not a limiting valve

It just simply shuts off one side when it senses pressure one side & not the other

they Often lock up with the piston inside jamming at one end when people bleed the system incorrectly

sometimes you can "free" them up by removing it,,, dropping it on the floor onto the right end,,, to (attempt) to jar the piston free,,,, (Sometimes)

The master cyl sizes & the wheel cyl sizes in this type of system are appropriatley sized to suit the pressures required for that particular mini.

Edited by MadMatt on 31st Mar, 2009.

www.miniman.com.au

"""LazyGoodForNothingSmartArseKnowItAllBackYardMiniMechanic"""

little drawing is this right ? prob im asking is were to run rear line from ?http://i650.photobucket.com/albums/uu229/minivanrick/turbobraking001.jpg"

Edited by minivan rick on 27th Mar, 2009.

Don't go slow !!! Go Turbo :))))))

Jay,,, It`s all good & well having "Failure protection",,, "IF" it actually worked well,,, but "IF" (& that`s a big "if",,, & not a very common "if" at that, when you think about it) the front brakes lost fluid,,, ok then you just have rear brakes right???,,, now lets just say that your front brakes actually do fail from loss of fluid (for some weired & very un-common reason) ,,, then you end up spinning like a top down the road with absolutely no control cause you may as well as just hit the hand brake right? But in this instance you didn`t intentionally hit the hand brake & certainly didn`t expect it, so you`re suddenly & without warning, doing 360s in what-ever direction you were heading

single master systems have worked absolutly wonderfuly for litterally decades without much trouble at all,,, except for the age &/or poor maintenance of components & rust build up in the fluid system from the fact that most brake fluids actually absorb moisture from the atmosphere (great idea that,,, lets just make brake fluid absorb moisture just so that brake repair companys can stay in business & panel beaters eat well)

Why do you think they changed to a diag system after the front/rear split system??? Obviously the front/rear system was a little bit of a problem


The only good thing about it is "IF" (& that`s a very rare & un-common "IF") the rears lost fluid, then at least you`d have (maybe) front brakes working.

however,,, there`s really nothing wrong with the PDWA Valve,,, """if/when""" it`s all in good order,,, my main concern with these things is when the un-initiated try to bleed the system the wrong way & "CAN" (not saying always do, but "can") stuff up that valve & lock it up at one end,,, which , as it happens, is Very Common.

Drip, or gravity bleed them & you shouldn`t have a problem,,, if/when pressure bleeding them then release a front & a rear nipple at the same time.

otherwise ditch the thing & replace it with a joiner tube for the rear pipes ... & a "T" piece for the fronts.

brakes only slow you down

www.miniman.com.au

"""LazyGoodForNothingSmartArseKnowItAllBackYardMiniMechanic"""

Common misconseption that this little valve is a PDWA valve.

Pressure, Differential, Warning, Actuator. PDWA

how does it warn you? PDWA valves to not close off the faulty circuit.

This is a brake pressure reducing valve, it closes off the faulty circuit reducing further loss of fluid. It also reduces the effort to the rear wheels.

Look at it this way. if this valve does not reduce the effort to the rear wheels, what is ? its not the small and insignificant difference in master cylinder size, even then the older master cylinders were the same size for the front and rear. Early cars use a different wheel cylinder size where a PDWA valve is used, later cars used a larger wheel cylinder with the Pressure Reducing Valve.

This valve is not a PDWA valve, and it is a pressure reducing valve. Feel free to try and disprove this, as it is in clear print in various workshop manuals.

Edited by Sprocket on 27th Mar, 2009.

Sprocket,,, just curious,,, how many of these valves have you opened up ???

It`s interesting because of all the ones i`ve repaired & /or used simply as junction boxes over the years, none have had any "pressure reducer" or "pressure limiting" device inside them... Maybe the Pohmy ones are differnt to ours in Aus but as far as i`m aware they`re the very same item & p/#,,, I`m not sure you understand how simple these valves are,,, the cars that were fitted with these valves left the factory with the brake cyls sized correctly to suit.

There`s just 2 sections inside,,, both seperated by the floating piston,,, If there is pressure in one section & not in the other, the piston is pushed over by the pressured side to the side with no pressure & simply shuts off the ports on that side,,, that`s all,,, no other reducing or limiting device or valve or anything involved.

Could best be described more as a "Failure Conscious" valve than anything else & it certainly doesn`t provide any differential in braking power between those 2 sections,,, unless one side looses pressure.

Edited by MadMatt on 28th Mar, 2009.

www.miniman.com.au

"""LazyGoodForNothingSmartArseKnowItAllBackYardMiniMechanic"""

My front decided to leak once when i was driving through the moores.

It wasnt fun and this little mumbojumbo malarky, PDWA or not, did not work!

yeah James, they`re quite often siezed,,, &/or if you still have some pressure in that side, ((as in a small slow leak)) then there will still be some pressure until the system sucks enough air back in each time you release the peddle.

www.miniman.com.au

"""LazyGoodForNothingSmartArseKnowItAllBackYardMiniMechanic"""

Thats just it, its not a PDWA valve its a pressure reducing valve.

They are two different valves and look different too.

Im only trying to help, as if some one were to remove one of these on a tandem system without any other reducing method, might find themselves in scenery.

ok, it`s clear you guys hav`nt looked inside one

There is no such "pressure reducing" valve inside it.

There are (however) other such valves that do-->

"""A brake pressure control valve consisting in a combined pressure differential warning actuator (PDWA) and pressure conscious reducing valve (PCRV) in which the PDWA consists of a piston exposed at each end to fluid pressure of one brake system acting in combination with an electric switch in such a manner that if the differential pressure between the ends exceeds a certain value the piston is moved to operate the switch and give a warning and in which the PCRV consists of a piston or a number of pistons arranged within the PDWA piston to provide for control of the fluid pressure supplied to rear brakes of a vehicle to assist in preventing locking up, such control not being exercised in the event that there is a failure of the front brake system of the vehicle""" pictured here-->

But, the valve pictured in the first post on this thread is "NOT" one of those.

Edited by MadMatt on 30th Mar, 2009.

www.miniman.com.au

"""LazyGoodForNothingSmartArseKnowItAllBackYardMiniMechanic"""

The extract you quote states that a PCRV reduces the rear brake pressure. Are you saying that the valve pictured at the start of the topic is not one of those? Its certainly not a PDWA as it has no warning actuator on it.

Are you also saying Rover are wrong in calling it a pressure reducing valve?

Matt could still be right (and i trust he is tbo, havnt opened one of these myself) however:


diagonal split with a PROPER pdwa valve

f/r split with proper Pdwa valve including description


f/r split with the valve under discussion, no switch, including description.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

It pains me to see how long winded this topic is getting

Its a Pressure Reducing Valve, plain and simple

sorry people,,,

i was talking about the one that i posted a pic of being just the piston inside, i`m not going to bother editing it cause i obviously already look like a dork,

i chimed in after jay & was in diag system mode, i had a quick read back i can see where i`ve confused the issue,,, sorry,,, & then i stuffed up again with both the copy n paste of text, & the pick that i posted, I did a quick browse & picked the wrong text & pic, my bad, im was a little P!$$ed at the time

In the hope to make things straight,,, The valve in the very first pick is both a failure conscious & a limit valve,,, it`s not a reducer,,, it`s a limit valve,,, it has a valve in back end of it "Limiting" pressure to the rear wheels , much like the early rear frame mounted ones do & also has the failuer conscious section as well

The pic thst i posted is just a failure conscious valve (PDWA) there is no Limit or reducer valve in it at all & these are the ones i often use puely as junction boxes.

sorry to be a dick, Of course Sprocket is correct.... but the valve shown in the very first pic it`s not, what i`d call, a "reducer",,, Its more a combined "limiter & failure conscious" valve.

again sorry to make this topic drag on & on,,, i know it pains you Colin sorry i wasn`t typing to shit you off

www.miniman.com.au

"""LazyGoodForNothingSmartArseKnowItAllBackYardMiniMechanic"""