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dean1484
dean1484 UltimaDork
7/21/14 11:47 p.m.

My 94 mustang has never had any rear brakes since I got it. I have changed everything in the brake system. Lines (soft and hard) calipers proportioning valve master cylinder and nothing changed.

Then I did some homework and found that some one put the front calipers from a late 90's GT with the twin pot's and the rear are stock. The stoce ones for this car should be single pot.

So I tried a proporshining valve form a late 90's GT. No change.

So anyone have any ideas? Change the master? Is the master different from a94 standard mustang and a late 90's GT?

I looked in to changing the fronts back to the stock calipers for a 94 and it looks like I need to change the backer plates as well. Can anyone confirm this? I would like to keep the fronts as they are definitely an improvement over the OE ones for the 94 but if it there is no way to get the balance back with them then they can go away.

I was thinking of just tossing the whole system in the trash and starting over. I would either go completely aftermarket and make it adjustable or go back to completely stock something from a later ford of some kind.

Anyone got any ideas opinions as to where to go with this. I don't need fancy high performance brakes I just want a reliable well balanced brake system that if it can be upgraded for reasonable cost I would gladly do it.

Could I take the brakes from a Crown Vic and put it in it? Or some other more modern ford?

I like the car. IT gets decent millage and does not attract to much attention while still looking sporty but in reality it is just a nice highway cruzer that I would like to get the brakes sorted out. In its current state even driving in the wet is seriously dangerous never mind any kind of winter driving.

Will
Will SuperDork
7/22/14 7:58 a.m.

My knowledge of Mustang stuff isn't what it used to be, but when you say you grabbed a late 90s prop valve, how late? I think the GT may not have had twin piston calipers until 99.

stanger_missle
stanger_missle HalfDork
7/22/14 8:05 a.m.

Yep, twin piston PBR calipers. My '95 has them from a '99 GT. The later cars have a hydroboost system.

What is the issue? Poor pedal feel? Poor performance?

The_Jed
The_Jed UltraDork
7/22/14 8:46 a.m.

Have you tried scuffing the rear pads (or getting some new ones) and replacing or turning the rotors?

Is there any chance it has rear ABS and it's wigging out?

The_Jed
The_Jed UltraDork
7/22/14 8:48 a.m.

How about ditching the proportioning valve altogether? That's how my blue Lincoln was plumbed and I thought it felt pretty good.

iceracer
iceracer PowerDork
7/22/14 8:54 a.m.

Is it no brakes or just that the fronts are doing all off the braking ? A stock system is balanced to basically apply all four brakes together. Increasing the front braking power overrides that balance.

dean1484
dean1484 UltimaDork
7/22/14 8:55 a.m.

Rear pads, rotors and calipers were / are new

I have thought of ditching the valve. Not tried it

The issue is there is very little if any rear brake force to the rear.

Peddle feel is excellent just that 99% of the stopping force is being done by the front. I have access to a brake testing machine that you drive on and hit the brakes and there is vircahlly zero rear brakes in the car. It drives like it as well

The_Jed
The_Jed UltraDork
7/22/14 9:11 a.m.

Make the best of the situation, do this:

stanger_missle
stanger_missle HalfDork
7/22/14 9:16 a.m.

Does the car have ABS? It seems like a line or orfice is blocked and not allowing pressure to the rear circuit of the car.

Will
Will SuperDork
7/22/14 9:25 a.m.

I doubt the prop valve could skew things quite this badly. I have 00 Cobra R brakes (4-piston Brembos, 13" rotors) on the front of my Supercoupe and I'm still using the stock prop valve with no problems.

Leafy
Leafy Reader
7/22/14 9:30 a.m.

Are the rear brakes doing anything? Are the pistons or slider pins seized?

dean1484
dean1484 UltimaDork
7/22/14 4:56 p.m.
Leafy wrote: Are the rear brakes doing anything? Are the pistons or slider pins seized?

All are / were new and working perfectly.

The rear brakes are working enough to barley clean off the rust from the new rotors. I know it is probably a bad idea but I was thinking of removing the Prop valve and teeing the front and rear lines from the master together and then putting another t to the bottom of the first tee and attaching the front and rear circuit. I don't like the idea of if one system gets a leak I loose all brakes but at the moment if I loose front brakes and will basically loose brakes AND at the moment it is really no fun to drive and like I said down rite dangerous on wet or other less than optimal surfaces.

dean1484
dean1484 UltimaDork
7/22/14 4:58 p.m.
The_Jed wrote: Make the best of the situation, do this:

V6.. . . . But it does get high 20's around town and low 30's on the highway.

dean1484
dean1484 UltimaDork
7/22/14 5:03 p.m.
Will wrote: I doubt the prop valve could skew things quite this badly. I have 00 Cobra R brakes (4-piston Brembos, 13" rotors) on the front of my Supercoupe and I'm still using the stock prop valve with no problems.

Ya but does the super coup have the same brakes as the later mustangs? It is a heavier car yes?

I just looked at the sheet I got with the car that lists the mods by the previous owner and this is what he sais about the frount brakes

Previous Mustang Owner said: 1999 V6/GT Front Calipers and Rotors (PBR Twin Piston, w/ stock pads)

They are the PBR twin piston calipers I have looked.

I am wondering if the 99 and up masters are different and due to the much larger volume of the front brake pistons the prop valves are putting all the fluid to the rear. Thus I would need a master with a larger rear capacity to make up for this. If I removed the prop valve this would probably determine this. I think I did this already but I don't remember for sure. Before I do this does this make cense?

Leafy
Leafy Reader
7/22/14 5:04 p.m.

Have you considered the rear brake calipers from the 99+?

dean1484
dean1484 UltimaDork
7/22/14 5:12 p.m.

I just looed it up and with out ABS (for both the 99 and the 94) they are different part numbers for a 94 V6 mustang and a 99 GT with the PBR calipers in the front.

94 v6 mustang MASTER = Fenco Part # nm2693

99 GT Mustang MASTER = Fenco Part # nm4031

The bad is that it is $85. I don't really want to toss that $$$ at it with out knowing for sure that it is the problem.

I would rather go to something aftermarket with duel resivwars that I can adjust independently and completely separate the systems even if it is 2x the $$$$ (probably optimistic in the $$$ department but )

Kenny_McCormic
Kenny_McCormic PowerDork
7/22/14 5:12 p.m.

It it has that stupid Ford rear ABS setup, get rid of it. Install a cheap adjustable prop valve or update the whole system to the later stuff.

dean1484
dean1484 UltimaDork
7/22/14 5:12 p.m.
Leafy wrote: Have you considered the rear brake calipers from the 99+?

No I should look and see if they are a different part number I don't think they are. I will look

EDIT I looked and they are different part numbers as well.

Leafy
Leafy Reader
7/22/14 5:14 p.m.
dean1484 wrote:
Leafy wrote: Have you considered the rear brake calipers from the 99+?
No I should look and see if they are a different part number I don't think they are. I will look

If they're not different then akjsdfgj;hasdgkjasgkjajksdfjabsjdgjasdgjkasjkdgfjsfagbjasgdbjkasgdjkbkbjasfdjh;asdajkhsdghjkasdfgjasdgbjkasjkbd you're doing something else wrong.

dean1484
dean1484 UltimaDork
7/22/14 5:15 p.m.

EDIT I looked and they are different part numbers as well.

dean1484
dean1484 UltimaDork
7/22/14 5:15 p.m.

No ABS on the car

dean1484
dean1484 UltimaDork
7/22/14 5:16 p.m.

So with different part numbers all the way around I guess I should either.

A replace the fronts and get the mounting brackets to put the OE ones back on to match the master and the rear.

OR

Get new rear calipers for a 99GT and a new master for a GT (if they bolt up) to make everything match the front PBR calipers

Leafy
Leafy Reader
7/22/14 5:17 p.m.

Well to me it sounds like the easy button is to just install the 99+ rear brake stuff,along with the 99 prop valve and then also fine out if the 99+ have a different bore master cylinder.

dean1484
dean1484 UltimaDork
7/22/14 5:17 p.m.
Leafy wrote: Well to me it sounds like the easy button is to just install the 99+ rear brake stuff,along with the 99 prop valve and then also fine out if the 99+ have a different bore master cylinder.

Any idea where to get that info?

Leafy
Leafy Reader
7/22/14 5:22 p.m.
dean1484 wrote:
Leafy wrote: Well to me it sounds like the easy button is to just install the 99+ rear brake stuff,along with the 99 prop valve and then also fine out if the 99+ have a different bore master cylinder.
Any idea where to get that info?

Normally master cylinders seem to be stamped with their diameter. If not. You are sitting in front of a computer with the infinite knowledge of the whole universe at your finger tips. Someone has already done all of this research that we're spit balling at. You just have to find it. You'll probably find some old thread from 2005 on a forum that lists every single brake part interchange on the mustang.

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