Brake Proportioning Valve

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Page created by T June 11th 2008:

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Dissembled Brake Proportioning Valve. Click to Enlargen. Photo by Brett bf6379.

Brake Proportioning Valve:

Description:

The Brake Proportioning Valve is responsible for preventing Rear Wheel Lock-Up under brakingby limiting the amount of fluid pressure sent to the Rear Brakes.

Brake Failure:

The Proportioning Valve also serves as a Fluid Loss prevention device in the event that the Front or Rear Brakes suffer a total fluid loss.Under this condition a Piston in the Proportioning Valve slides towards the faulty section of the Brake circuit and prevents Brake Fluid from flowing towards that circuit and being lost. 

Factory HG Premier. The Brake Proportioning Valve is mounted underneath the Master Cylinder on the left side of the image. Click to Enlargen. Photo by Ayios.

Simultaneously a Switch in the Proportioning Valve is activated which illuminates a Dash Lamp Warning of Brake Failure. 

External and Internal Proportioning Valves:

The early style (pre-WB, pre_VB) is a seperate unit often bolted underneath the Brake Master Cylinder.The later style (from VB and WB on) is built into the Master Cylinder. 

Brake Relines and Brake Pad Maintenance:

When a Brake Reline or Disk Pad replacement is being performed on a Car, the Proportioning Valve can become activatedand illuminate the Brake Warning Lamp on the Dash. To fix the problem it is necessary to unscrew and remove the Warning Switch, then fully reinstall it. This will reset the proportioning valve. 
This Master Cylinder does not contain the Brake Proportioning Valve which is usually mounted underneath. This style was used on early HZ and UC as well as  earlier models. Click to Enlargen. Photo by MyEHHolden.
  
This Master Cylinder contains the Brake Proportioning Valve. This style was used from WB and VB upwards. The Brake Failure Switch can be seen in the centre of the unit. Click to Enlargen. Photo by DannyW.
 
This Master Cylinder contains the Brake Proportioning Valve. This style was used from WB and VB upwards. The Brake Failure Switch can be seen in the centre of the unit. Click to Enlargen. Photo by DannyW.
 Originaly submitted by mackv8: information for you (and others)re proportioning valve's hq to hz.(wb are in the master cylinder). 6 cyl and 8 cyl are the same, they are dependent on whether you have disc or drum on front and disc or drum on rear, and then in if its a sed,2 door coupe or 4 door (not statesman). statesman, wagon,coupe ute, panel van or 1 tonner i will take it as you have a kingswood 4 door sed with disc on the front and drum on the rear, you will need a silver(or natural aluminum )colored one. 
And you want more, on hq the valve is only a brake fail warning switch the proportioning valve is only on disc front drum rear and it is in the rear brake line approx under the b pillar, the electrical switch on hq hj hx is a single terminal switch, on hz wb there are two terminals on switch (on hx statesman's with anti lock rear brakes the are two terminals on the switch)in hj hx hz the proportioning valve also has the brake fail as one unit. i have about 4 for a sed two for a statesman/wagon with 4 wheel disc i did have one for a wagon will have to have a look ( the pressers in the valve are different as per body style brake combo . you will need a black colored one check it for black/dark tinting.
  
Separate Brake Proportioning Valves. Click to Enlargen. Photo by Jason Ackland.
 
Brake Proportioning Valves. The Plastic Switch may need to be removed and replaced to reset the Switch if  Pressure has been lost during Bleeding. Click to Enlargen. Photo by Jason Ackland.
  

Proportioning Valve Numbers:

I found the information I was looking for and it says there are 3 different proportioning valves. P 7256 suits HZ sdn and the crack point is 225 psi.
P 7259 suits HZ wagon and utes etc and the crack point is 350 psi.
P 7305 suits 4 wheel disc brakes and the crack point is 450 psi. My understanding on this is that rear disc are not self energizing like drums and
they need higher pressure settings to stop rear wheel lock up.
These are old PBR numbers so if they are still available I do not know.
Cheers Paul. 

Links:

Jason Ackland's Shed

Terms:

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