well, I need all your help again. I installed an 87 tc rearend with disk brakes in my 88 sport over the last two days. my father and I bled the rear brakes only untill there was no air, and the pedal was firmer. when I started it up, the brakes were SOFT. the pedal went a good 75% before they started to engage. drove it a bit, then bled them again. they firmed up and then went soft again after starting it. what could cause this?
thanks for the help.
Did you do anything with the stock brake proportioning valve?
The MC is probably a bit small for your set-up now too.
well, to tell you the truth, I couldnt find the stock prop valve, I dont think mine had/ has one. I put a jegs adjustable prop valve in line to the rear brakes right under the metering(?) block. ( that thing right under the m/c)
thanks
That IS the stock proportioning valve.....
so, what do I do with it? it feeds the front as well as the rear, and isnt that where the piston is?
You did almost everything correctly. :)
The stock metering (prop) valve has to be gutted. Right now it wants to meter the fluid just as it does with a stock disc/drum setup. You need more fluid flow to the rear. The adjustable prop valve will do that, but first you have to gut the stock one.
You need to get a special fixed plug from Ford Racing, p/n M-2450-A. Then, remove the plug from the front (faces front of the car), gut the plunger and spring, put in the new plug, bleed the brakes, and that should help things significantly.
-tastic. that explains alot. thanks guys. I dont know if it means anything but the brake pedal firms up if i pump'em.
if im making very little sense, its because im doing all this while running a temp, ugh
You may still have a low pedal when all said and done though. It is possible though that you probably just could not get enough flow to the rear to bleed them properly
Ok so basically you are turning the stock prop valve into a "distribution" block?
I run a tc rear all stock no mods (for about 10 years now) and the pedel is fine. You really have to bleed the out of it. I also bleed all 4 wheels not just the back
I still have to wonder how some of you guys can convert to rear disc and still have a "good" pedal on the factory master cylinder...the stock MC bore size is marginal at best for four wheel disc.
I remember reading somewhere that the 86 and 87 Turbo Coupes had a smaller master cylinder than the 88. I just finished putting in a four wheel disc into my 88 LX and used a 88 proportioning valve. I posted a question as to the part number to see if it was indeed from a Turbo Coupe.
Weren't all 87-88 T-coupes ABS brakes?
yessir, 4 wheel ABS....but the ABS will be non-functional on a TC rear swap...
It'd be way too much of a hassle to get it to work...and it's somewhat problematic anyway, IIRC-i might be talkin' :bs: about that though.
I've got a TC rear I'd like to put in mine, but some ass-pirate :flame: cut the e-brake cables some time long before i got my parts TC...
As I'm going to be doing this swap soon, I was wondering: Will a master cyl from a 94-95 Mustang without ABS work? I've heard of people using Crown Vic and SVO master cylinders, but wouldn't a 94-95 Stang unit be better (provided it would even fit)?
I've heard of using Crown Vic MC's even on stock brakes becuase thier larger bore increases pedal feel.
SVO/Crown Vic master cylinders = 1983-86 cars (2-line setup, cast iron)
For the 1987-up cars (3-line setup, aluminum), the theory is that the stock m/c bore is good enough for rear discs. For fluid capacity I would tend to think that's probably true enough, since it has a single large reservoir, but the problem happens when you have a glitch like what's being talked about here. It's like, where to start tracking it down? I've always believed that you have to look to the oldest parts of the system first and replace them. And almost all the time, the oldest parts are the booster and master cylinder.
The booster thing is sort of borderline: there is enough vacuum produced to keep the brake system working correctly, even going drums to discs. But more boost is always better. So looking at Cobra boosters is usually first on the list and I can't disagree with that line of thinking. However, I am still running my stock 20-year-old booster with the full Cobra 13"/11.65" discs and pedal feel is outstanding. So the booster isn't the issue unless it's leaking, and you'll hear that in the cabin.
So it's on to the m/c. Remember, more bore = more fluid displacement = lower pedal feel. Less bore = less fluid displacement = better pedal feel. The key is to find the right bore (about 1" to 1-1/8" seems to be about right) to balance the system correctly. I like the Mustang suggestion Carm, so long as it's not from a car with the Hydroboost system, I think it would probably work. The p/n will probably interchange with something else, too, knowing Ford.
About the prop valve: a few people have reported (even on this board) that using a stock TC prop valve works fine. And it makes sense since it's set up for a better front/rear bias. But also remember that TC's had larger brake lines going to the rear. Still, it's a practical solution and is much less hassle than going through the FRPP plug/adjustable prop valve/brake line jumper thing. But that also has its merits for being able to fine-tune the front/rear bias. I have the adjustable setup on the convertible and honestly, I haven't touched it in over 7 years. It's working great and I don't see the need to continually monkey with the settings.
The bad news is, going from rear drums to discs on a Fox vehicle usally leads to a Frankenstein-type braking system. The good news is, there is ALWAYS some kind of Ford vehicle part that can provide a solution to a problem.
i swapped mine about two months ago and bled the out of all four wheels and mine has never had a problem.