16 replies to this topic

[UC Peter]

In the process of upgrading my front brakes. I’m using a Vari Race brakes kit. The car originally had 4 wheel disc so I was under the impression I hopefully wouldn’t have to change booster or master cylinder. The install was pretty pain free but now it’s all done and bleed I’m having brake bias issues. Rears are locking up before front after a fair bit of bedding in! Has anyone else had this issue and what is the fix? Also when bleeding the front or the back the small reservoir in the master cylinder drops! The large reservoir always stays same level which does not make sense, is this right. I have a torana book and the plumbing from master cylinder to proportioning valve is correct. I’ve also checked other Toranas and the plumbing is the same! Any help would be appreciated.
Cheers Peter

[axistr]

If the front reservoir in the brake master cylinder is not dropping in fluid height during bleeding than you must have an incorrect brake line hook up. Its possible to have internal bypassing of fluid in the proportioning valve but very unlikely to be enough to have the front reservoir not change level to some degree. You would also notice a slow sinking of the brake peddle when constant pressure is exerted. If you keep bleeding the front brakes on both sides and the front reservoir never changes level than your problem must be an incorrect brake pipe hook up. 

[UC Peter]

The brakes worked fine before the upgrade, now i have the issue! Like i said pipe work is as per the book. How do you attach pics on here? 

[axistr]

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Your brake master cylinder should look similar the one in the photo above UC/A9X with incorporated proportioning valve. You can see one pipe is connected directly to the front of the master cylinder for the front right brake. The left front brake is connected to the front and from underneath. The rear brakes are plumbed up from the one rear port on the master cylinder. This rear brake pipe continues to the rear and to a T-piece fitting on the diff housing for left and right rear brakes. 

 

If you open one front and one rear bleed nipple at the same time you pedal should sink all the way to the floor. If it only go half to 3/4 of the way down your hook up is incorrect.

 

Tests 1) Are you getting a good brake fluid flow when bleeding at every brake calliper and solid brake pedal with all bleed                    nipples closed.?   

 

         2) Get someone to press the brake pedal down lightly and try and turn each wheel by hand. If you have a free turning 

             wheel the problem is with that circuit. ( check for blocked or kinked brake pipes, hoses or ports and correct pipe                     hook up).   

 

         3) Check how each brake calliper is bleeding (flow). The brake booster push rod maybe ridding on the master              

             cylinder piston not allowing fluid to bleed from the front master cylinder compartment (sticking piston) or       

             proportioning  piston jammed towards the front brake circuit.   

 

 

 

[Balfizar]

Sounds like the proportioning valve "brake fail" piston is orientated - moved - and is blocking fluid transfer. check 3) above.
Use a meter to check continuity on the brake fail circuit, no resistance (closed circuit ) between the body of the Master cylinder and and the pins of the connector  of the brake fail switch.                                         

Edited by Balfizar, 14 June 2022 - 01:00 PM.

[Heath]

I do wonder whether you'd want an adjustable (aftermarket) proportioning valve if you're making such drastic changes to brake hydraulic ratios, anyway? I mean with 6 pistons on each caliper, these look nothing like what a Torana came with originally. I don't know what you have in the rear of this car... is it hydraulically similar in front-rear bias?

 

Maybe there's nothing wrong with the original style, but from the symptoms you've described, it seems likely at least your one is playing up.

[neglectedtorana]

Hi Peter,

 

When you reply you can click 'more reply options' the blue button at the bottom left and attach pictures.

 

You said the plumbing is correct from the master cylinder to the proportioning valve, to me this sounds odd. I thought the UC with 4 wheel discs didn't have a proportioning valve. A picture of your engine bay with the master cylinder and proportioning might help. If it has one I think it might have been incorrectly sometime in the past but I am not an expert on which model came with what parts.

 

Although it is nice to work from the point that the brakes were fine before the upgrade it is possible as Lenny said there could be a fault and also possible you didn't notice before but now with such dramatic changes it becomes evident, also possible you will need a bias adjuster as Heath said but before doing much I would want to check the proportioning valve you mentioned, as you can see from Lenny's pic he doesn't have one.

 

Hope you get a solution, have you asked Vari for help? They should have done this before.

 

Cheers, Tom

[Heath]

...but before doing much I would want to check the proportioning valve you mentioned, as you can see from Lenny's pic he doesn't have one.

I think Lenny's car actually may have a proportioning valve, but it's integrated in the same cast ally body as the master cylinder itself.

[axistr]

The pictured master cylinder in my earlier post is a UC spec (car has 4 wheel disc brakes), If you have something different than its been swapped out and you may have an incompatible system. UC and A9X have the proportioning valve incorporated in the master cylinder.     

[UC Peter]

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Hey Guys,

                Thanks for your help. I tried to attach pic i hope it works. I spoke to Vari and he wants me to a pressure test front and back at the same time, but i need to fix this issue with the back reservoir dropping when bleeding front brakes. He thinks proportioning valve as well. This is my plan.

1. Do pressure test on brakes as they are now. Any idea what PSI i should be getting?

2. Try to reset or replace seals in porportioning valve. How hard is this?

3. Do pressure test on again and compare results.

4. Once i have this info and still have same problem he has told me to talk to hydro boost down in Victoria. He seems to think he may suggest a master cylinder from a BA falcon?!

 

I am open to any other suggestions. This brake upgrade is not cheap and if i can get to work with my existing set up  that would be ideal. He did say that he has done this upgrade on many Toranas and every now and then you need to go down a different Master cylinder path.

 

Cheers Peter

[UC Peter]

This is what my UC book says. 

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[S pack]

08C6262E-8CD5-4097-A7E5-C86040C25D2C.jpeg

 

Hey Guys,

                Thanks for your help. I tried to attach pic i hope it works. I spoke to Vari and he wants me to a pressure test front and back at the same time, but i need to fix this issue with the back reservoir dropping when bleeding front brakes. He thinks proportioning valve as well. This is my plan.

1. Do pressure test on brakes as they are now. Any idea what PSI i should be getting?

2. Try to reset or replace seals in porportioning valve. How hard is this?

3. Do pressure test on again and compare results.

4. Once i have this info and still have same problem he has told me to talk to hydro boost down in Victoria. He seems to think he may suggest a master cylinder from a BA falcon?!

 

I am open to any other suggestions. This brake upgrade is not cheap and if i can get to work with my existing set up  that would be ideal. He did say that he has done this upgrade on many Toranas and every now and then you need to go down a different Master cylinder path.

 

Cheers Peter

The back reservoir, the one closest to the booster is the reservoir for your front brakes.
 

[UCgazman]

The pictured master cylinder in my earlier post is a UC spec (car has 4 wheel disc brakes), If you have something different than its been swapped out and you may have an incompatible system. UC and A9X have the proportioning valve incorporated in the master cylinder.     

Hey Lenny - the early UC's had the separate prop valve setup like LX (as UC Peter's pics above). The metric 'early commodore' style one you have (I have one on my UC too) was fitted from very late '78/Early '79 on IIRC...

Edited by UCgazman, 15 June 2022 - 08:34 PM.

[neglectedtorana]

I had presumed (incorrectly) that all UCs had the integrated proportioning valve.

 

Was the integrated proportioning valve master used with drum rear or only disc rear?

[UCgazman]

Was the integrated proportioning valve master used with drum rear or only disc rear?

Both

[Balfizar]

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This is what my UC book says. 

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Any chance of getting "all" of the "to reset brake light warning switch" Cheers. I can't find it in later manuals.

[UC Peter]

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