They don't work. Why the hell not?. They feel spongey, like they need to be bled. But I've bled them to death, changed the master cylinder for a new one, calipers are all freshly rebuilt, booster is working just fine.
The diff is a 9inch running XC rear calipers.
The master cylinder is the standard one for discs-drum setup (Covs and Repco both say that 4 wheel disc master cylinders are no different.)
I am not running a proportioning valve, or a residual line pressure valve in the arse end. As far I know the XC cobras didn't use an external proportioning valve (maybe it's built in the master cylinder), so neither am I - I'm jus attempting to replicate a system that works.
I haven't pulled the master cylinder apart, but it's like the rod isn't forward enough in the cylinder, if you know what I mean. I don't know a whole lot about brakes or the intricacies of how a master cylinder works and I cannot figure this out for the life of me.
The only thing is the handbrake isn't setup properly, but will be by friday. This should improve them but I doubt it'll fix 'em properly (the pads are still right on the discs, there's no gap, like the calipers aren't open execessively.)
I think I need to mess around with valves of some sort.
Anyone put 4 wheel discs on their falcon and had it work sweet?
I know that the rear brakes can be a real bastard to set up, and sorry, I normally get the mechaninc to do that one. With respect to the feel of the brakes, they should be excellent.
I rebuilt mine using 4 new rotors, all new parts (including new sleeves in the calipers) as well as a new master cylinder and I have never had a car with brakes as good as these are. Admittedly it is in a ute but it should not feel spongy.
My only real comments would be to make sure that the rears are coming on and you have correct vacuum. Other than that, take it to a reputable brake mechanic. The reason that I say this is that I once just could not get it right. Took it to the mechanic and bingo, there was some air in there that I had not gotten out.
I have discs all round on my XA and they work fine.
It has a new standard master cyl, standard booster and xc discs. No proprtioning valve or anything either.
If you aren't sure about your master cyl I would be checking that first. Another thing to consider is that your brake hoses aren't old and balloning or anything like that
THe XC with 4 Wheel Disks had the Brake Balabce built into the Master Cylinder (Clear Plastic Reservoir Type).
As XA Coupe said, check your Hoses aren't ballooning under pressure and need replacing (Don't forget the one from the Body to the Diff).
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well first off i'd use the vacuum brake bleeder if i were you, those things work a treat. if that doesn't solve the problem then i'd say its your master cylinder, from the looks of it i'd say it were of an even older falcon because most of the falcons i've seen are all running the plastic resevior type master cylinder
[QUOTE I am not running a proportioning valve, or a residual line pressure valve in the arse end. As far I know the XC cobras didn't use an external proportioning valve (maybe it's built in the master cylinder), so neither am I - I'm jus attempting to replicate a system that works.[/QUOTE]
You have basically replicated the LTD / Landau's braking system, the LTD was the first Ford with 4WDs - that's why there was so many rumours that the Phase 4 would have the same set up. I agree that it could be the rubber hoses ballooning but If it turned out to be the master cylinder being wrong for your setup - I would look for one from the LTD or a XB GT.
My first car was a XC Fairmont and I put a 9" disk brake diff under it, the diff actually came from a XB era LTD and If I remember correctly the proportioning valve did need to be changed.
Sounds like you're on the right track - hope you get it sorted soon.
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