PDWA or PDWA/PCR valve ?

[hurbie]

hello all , 

 

since the Eurover is a bit of a bitsa , i'm not to sure wich valve to fit , the french donor had a big brake booster and a PDWA/PCR valve , but the original scottisch 110 has a smaller brake booster (so should use only a PDWA valve (not shure , because it was removed before i got the car)

on my own 3 door 110 , it only has the PDWA valve .

should i just use the PDWA valve (then i  need to find one) , or should i use the PDWA/PCR valve (then i would need to find a rebuilt kit i think) 

 

any thoughts ?

[Snagger]

I would omit both and just fit a level sensing reservoir cap from a late Defender/RRC/D1.  Simpler plumbing and faster and more reliable leak indication.

[miketomcat]

As snagger says delete and fit a sensing cap. I didn't fit it when I built the ibex as it only tells you the brakes have failed and the cap does the same job. I think some early 110s it turned the brake lights on to but I might be thinking of something else.

Mike

[hurbie]

i understand the working of the valve ,and i do know you can use a cap on the master cilinder

 the question is , do i need the PCR valve ,this reduces the brake pressure to the rear wheels preventing them from locking-up , might have something to do with the bigger servo ....

bit it might just be a country specific requirement ...

[Snagger]

On a short wheel base, a bias valve is needed.  110s don’t have bias valves, as I understand it.  The PDWA valve does not provide any biasing.  The biasing is not because of servo size or boost, but to ensure the rear brakes of the lighter, shorter models don’t lock up before the front brakes.  Front brakes on a 110 are substantially bigger than on a 90 or 100” model, and the 110 rear brake discs are the same as the shorter models.  That provides the bias needed, the extra vehicle weight and the increased moment over the rear axle helping keep the tyres in better contact with the road too.

[Retroanaconda]

18 minutes ago, Snagger said:

Front brakes on a 110 are substantially bigger than on a 90 or 100” model, and the 110 rear brake discs are the same as the shorter models.

I’m not sure where you are getting that from but it’s wrong for most Defenders.

From 1991 all 90/110/130 have the same size front discs. 110/130 got vented as standard, whereas it was an option on 90, but all same diameter and calipers.

Rear brakes on the 110/130 are the same diameter as the fronts, just with smaller two-piston calipers rather than bigger four-pots on the front. The 90 uses a smaller diameter disc, same as the Disco/RRC.

Obviously all had rear drums until 1993/1994 and the sizes were different same as the discs. Before 1991 90s had smaller front discs than 110s as well.

The brake bias valve (‘G’ valve) is simple to fit and is all that’s required on a 90. For a 110 you don’t need any valves at all, just the reservoir cap as above. There is good info on the different braking systems in the workshop manual. 

[miketomcat]

Just to add to retros comment pre 91 the 90 had smaller front calipers than the 110 but post 91 ish they fitted 110 calipers to the 90.

Mike

[Wytze]

On my 109 i used all the 300 tdi stuff, brake wise.  110 front's 110 rear disk's and 300 tdi master on the big booster.  The brake's work really well, and the bias is spot on.  

[Snagger]

OK, I was misinformed and had the wrong idea for a long time - I thought the 110 rear discs were the same as 90, RR and Discovery front discs.  I have never had the systems apart on two cars simultaneously to compare.  Certainly, the discs and callipers on RR/D1 are smaller than a 110, but I never made the comparison to the 90, just relied on what a mechanic friend had assured me.  When I fit the D1 brake system to my coiler axle 109, the new discs had the same part number on the front as Defender rear, but I was told in the shop 110 rear, so I suppose that consolidated the misunderstanding.

Anyway, as I said, I’d recommend not fitting valves on the 110, just the level sensing cap.

[Wytze]

10 hours ago, Snagger said:

OK, I was misinformed and had the wrong idea for a long time - I thought the 110 rear discs were the same as 90, RR and Discovery front discs.  I have never had the systems apart on two cars simultaneously to compare.  Certainly, the discs and callipers on RR/D1 are smaller than a 110, but I never made the comparison to the 90, just relied on what a mechanic friend had assured me.  When I fit the D1 brake system to my coiler axle 109, the new discs had the same part number on the front as Defender rear, but I was told in the shop 110 rear, so I suppose that consolidated the misunderstanding.

Anyway, as I said, I’d recommend not fitting valves on the 110, just the level sensing cap.

On the late salisbury rear axle , that i have under the 109, there are early 110 solid front disk's 

[simonr]

On my last but one 110, I found the back end was kind of lively under breaking in wet weather.

I retro-fitted the G Valve (PCR) and it made the world of difference!  It always struck me as odd that even on 110's the bracket was included on the chassis rail, but the valve omitted.  Probably different legislation in different countries?

The PWDA valve was nothing but trouble!  The internal piston often seemed to jamb at one end or the other, which reduced the flow to the front or rear.  I ended up just removing the piston & fitting a replacement cap as others have suggested.  The PWDA switch would tell you when your brakes have failed - but that was generally obvious from the fact the brakes didn't work!  The level sensing cap at least gives you a bit of warning before the brakes fail.

[ped]

i'm currently at the stage of doing my brake lines and the talk of ommitting the pdwa is interesting
i've never had issue with it so i'll still use it i think but the tip about removing the piston if it does cause issues is handy

[hurbie]

1 hour ago, ped said:

i'm currently at the stage of doing my brake lines and the talk of ommitting the pdwa is interesting
i've never had issue with it so i'll still use it i think but the tip about removing the piston if it does cause issues is handy

if it is working as it should be , it doesn't cause trouble . and in my world it's faster at sensing something is wrong with the brake's before the sensing cap does (that onnly works when most of the fluid is gone , where the PDWA works almost instantly ...

it could give trouble getting air out of the brake's , i read somewhere to put a temporary plug in where the sensor is , to stop the piston moving.

 

i might put the PDWA/PCR valve from the french car in , "IF" i can find some seals to rebuild it .

[Snagger]

2 hours ago, ped said:

i'm currently at the stage of doing my brake lines and the talk of ommitting the pdwa is interesting
i've never had issue with it so i'll still use it i think but the tip about removing the piston if it does cause issues is handy

Don’t do that - if you remove the innards, front and rear systems will be bridged and a leak in one side will knock out both front and rear brakes.  
 

Ensure you either have a functional PDWA valve or if seized, that, it is centralised so that both circuits are open and independent.  In the case of the latter, the level sensing valve would be important, since the valve shuttle and sensor will be jammed.  If the valve is seized, you are better off removing it entirely so that corrosion or deteriorating seals don’t clog the rest of the system.

[ped]

That is a consideration afaik it all works fine 

If i find it stops working I'll machine up a block to replace it