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Discussion Starter #1
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?
 

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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.

Anyway, best of luck

Paul
 

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Discussion Starter #3
Exactly, discs all-round, I should be smashing my head into the windscreen as soon as I touch the brakes. As it is now the car just kinda rolls to a stop, with my foot to the floor!

I don't wanna be a pain, but yours works. So can you give me the part number of your master cylinder, and also, are you running any proportioning valves etc in your lines?

Otherwise yeah, I might just have to take it to a proper brakes specialist and get them to figure it out.
 

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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
 

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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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Munch Munch Rice 4 Lunch
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what are you using to bleed your brakes, are you using a vacuum bleeder or the old technique of pumping the brakes up then bleeding out into a container or sorts?
 

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Discussion Starter #7
From memory we bled the brakes by pumping them. I've got a vacuum bleeder though.

I'm not using the plastic resovoir type master cylinder. Here is the master cylinder I am using (I resized them, they aren't so massive it'll take a week to load)

http://home.iprimus.com.au/mahu_/mastercylinder1.jpg
http://home.iprimus.com.au/mahu_/mastercylinder2.jpg

The master cylinder is brand new. Is this the cylinder the rest of you are using?

If the cylinder is correct then I will check the softlines tomorrow.
 

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Munch Munch Rice 4 Lunch
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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
 

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[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.

Paul B
XR6WGN
 

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first thing i would do is upgrade to the xc/zh booster and master combo, but with the master cylinder design u have it will work on discs and drums as well as dics and discs (did on xb's) but there is a restrictor you need to drive a self tapper into then yoink out with pliers this could be your problem, also are you using some shit pads like dons or other $20 variety if so this can cause the spongeyness as well as no stopping power.

only other thing i can think of is did you cook them during the run in process? if so all of the things you mentioned will be present.
 

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Discussion Starter #12
I did a quick check on the car today. The softlines are all fine. But I opened up the master cylinder and when the pedal is first depressed, brake fluid is forced back into the resovoir.

I have a strong feeling it's gonna be the master cylinder. When I bought mine they said it was fine for disc-disc brake setups, but I'd only heard 'rumours' of pulling out the restrictor. My mate has a spare XC cylinder in his shed, so I'll see what happens.

I'm using bendix pads.

Cheers for the help guys
 

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I did this setup years ago on an XA and it worked fine with the XA master..I will say though i did have some trouble bleeding the rear calipers, but then it was good.It took prob about 10 gos at getting all the air out.I would go for a drive ,come back and get some air out until it was clear.I kept going until all the air stopped..
Since you say the pedal is on the floor i'd say you either have a master prob or still some air in the system.
Just an idea,are the calipers assembled with the bleed nipples at the top.I saw some coomodore rear discs a while ago that had been assembled with the incorrect calipers and brackets mixed up ,so the bleed nipples were on the bottom.That would create some interesting problems ..
 

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Sometimes when you fit new brake pads to a car or even replace them with good second hand ones [ Many people do this] , Your brakes can be very spongy or sometimes barely work till the calliper pistons return properly , or the brake shoes bed in to your rotors etc...Its happen to my car before.
 

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do these masters have an adjuster for the push rod that pushes into the master? i know on my old landcruiser that was the problem that took me ages to fix, adjust the push rod into the master, so the brakes "come on" earlier, and less fluid is forced back into the resevoir
 

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EyeEatRice said:
I did a quick check on the car today. The softlines are all fine. But I opened up the master cylinder and when the pedal is first depressed, brake fluid is forced back into the resovoir.

I have a strong feeling it's gonna be the master cylinder. When I bought mine they said it was fine for disc-disc brake setups, but I'd only heard 'rumours' of pulling out the restrictor. My mate has a spare XC cylinder in his shed, so I'll see what happens.

I'm using bendix pads.

Cheers for the help guys
I'm running a XD disc brake master and booster on my XA coupe. I did install a Wilwood proportioning valve because I'm running a 1995 Mustang Cobra 8.8" solid axle with 11" discs. A proportioning valve should not affect the pedal feel BUT it should affect which brakes lock up first. 2 quick tips that I was taught years ago:

1) Rubber brake lines will breakdown from the inside out so never trust a "look and feel" test. If you don't know the history of the brakes and you can't determine the age of the hoses, replace them. Those are cheaper than a wreak a and a heck of a lot cheaper than a funeral.

2) When you bleed your brakes, DON'T "pump" them up. Get a mate to help. Depress the brake pedal and hold it down while your mate opens the bleed screw. DO NOT release the pedal until he closes it. Then, release the pedal slowly and depress it slowly one time and have him open and close the bleed screw again. Repeat as needed. Make sure you don't bleed the MC dry and be sure to start at the left rear first, then right rear, then left front and finally right front. I know, I'm beating a dead horse but you would be amazed at how many people don't know what order you bleed the brakes.

--J
 

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You have air in the lines.
When I did my XB I pumped a litre through and still had air. Keep going, and going like XAFALCONGS says in #2. I actually pump 3 times then hold, whilst i open and then close the bleeder.
One trick is to have a spanner on the bleeder with a bottle with brake fluid down the bottom. Have the bleeder only just open and keep pumping through (refil the master 3 times), but always finish as xafalcongs says.
 
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