HQ Brakes

[BILLY BLACKARROW]

Hi all
I am having trouble with my brake setup .I am running hq brakes all round front are boosted by vh40, and proportioning valve I have great pedal pressure BUT the front wont release when you take your foot of the pedal, back are fine, I have been told that there is a one way valve in the booster that shouldn't be there is this correct and if so where is it, any other Idea's I have been to a brake specialist but they know nothing.
BILLY

[Craig Allardyce]

Billy if your running a standard master cylinder for a FB/EK you'll have to remove the minimum pressure valve in the bottom of the bore of the master cylinder. The valve is designed to hold a very slight pressure in the brakes system when the brakes are released. This is done to hold the cups in shape and against the wheel cylinder bores to reduce leakage. If this valve is left in and you run discs it will cause the disc brakes to lock on. If your running some other type twin circuit master cylinder make sure its disc and drum compatible, not drum and drum like some HQ's were.

[BILLY BLACKARROW]

Thanks Craig
I am pretty sure it is disk / drum compatible but how do I check the bloke that did the brakes for me is no longer contactable
BILLY

[Craig Allardyce]

What type of master cylinder are you running?

[BILLY BLACKARROW]

I dont have the car at the moment but can send photos of the setup later
BILLY

[Craig Allardyce]

OK, I'll check in the meantime but I'm not aware of any check valve in the booster that would cause the problem. Is this happening with the engine running or not.

[BILLY BLACKARROW]

I dont know if this will help or not









I dont have the engine in the car
BILLY

[Dirty Grey]

Hi Billy Blackarrow your problem could be from the master cylinder being for a car with four wheel drum brakes.Also the proportioning valve should be before the power booster as you have boosted pressure going into the front half and not boosted in the back half,if that makes sense. Another thing is some of the master cylinders the ports are reversed to the normal front port front brakes rear port rear brakes. Hope this is some help.cheers Rex.

[Craig Allardyce]

Dirty Grey is dead right. Generally speaking the larger reservoir section of the two is the front brakes. Some master cylinders had equal size reservoirs for all round drum set ups. If for drum there should be a residual line pressure check valve in that particular outlet for the drum brake rear (or both for drums all round). I would get the part number off the cylinder and check.
I definitely agree that you shouldn't be running only boosted pressure through half of the proportioning valve. These valves were designed to run equal inlet pressures to maintain correct balance on the piston and to control correct proportioning of the brakes front to rear.

I've attached a picture of a Torana master cylinder showing the check valves in the outlets.

Master[1].jpg (45.37 KiB) Viewed 3080 times

[EK JAY]

some good info in these article's may help

http://www.hoppers.com.au/brake%20kits/ ... 0pumps.pdf

http://www.hoppers.com.au/stoppin%20holden.htm

[EK JAY]

Hi all
I am having trouble with my brake setup .I am running hq brakes all round front are boosted by vh40, and proportioning valve I have great pedal pressure BUT the front wont release when you take your foot of the pedal, back are fine, I have been told that there is a one way valve in the booster that shouldn't be there is this correct and if so where is it, any other Idea's I have been to a brake specialist but they know nothing.
BILLY

you may have to adjust your pedal back a bit so there is a little bit of movement when you put your foot on the brake pedal
so there is movement before the pushrod go's into the master cylinder that way when you take your foot off it release's the pushrod fully and
is not still pressing on the cylinder hope this makes sense may not be the problem but worth a look
Jay