Help on lousy disc brakes

I just took my brother's Falcon for a ride while he was away. He just got it back on the road and it's a fun car, except the brakes friggin ****! We went through the work of putting discs on it and I think the system could possibly be worse than before with 6 cyl drum brakes. I am concerned for his safety since he drives like a maniac, and of others. I'll also be driving the car daily after he goes off to school.

The pedal isn't really soft, just spongy. For a manual braking system, the pedal doesn't feel hard at all, it feels like it has power brakes. The wheels will not lock up and I have to press it down kinda hard to stop. Sort of hair-raising.

The system consists of mainly Ford Granada parts which was the donor for the conversion.. It has the rear axle/brakes, front rotors, calipers and spindles and master cylinder. The car also has a Wilwood proportioning valve and a line lock. 99 percent of the lines on the car are new, the system has been bled repeatedly, no air in the lines to speak of. I can recall driving the donor car and remembering that the brakes were ****y, but all parts on the current system are new or rebuilt. I figured it had a bad master cylinder on the old system.

This is a much lighter car than that Granada, I would have thought the braking would have been supurb. I was thinking if I put a beefy master cylinder in and rebled the system it would be better unless there's a curlprit. Perhaps one from an 80s 3/4 ton Ford van or something? Or other ideas? Thanks

 

Sounds like there might still be air in the system. Try rebleeding it. Also make sure that the bleeders on the front calipers are to the top.


jerry

 

We may bleed the system again tomorrow. He took me for a ride in it and the brakes do lock up, I suppose I wasn't pressing the pedal hard enough. It just feels wierd, I had a Ranchero with the same setup and it didn't even feel similar, and my truck has manual drums so I am use to them. Just strange....

Would a bigger bore M/C make some better braking, though? Would it be worth the effort?

 

stock pedal? how long [in inches] is the pedal-from pivot to pedal?
I didnt hear a booster in there????

 

Are you running 'Silly-can't' fluid?Makes em hard to bleed sometimes

You need a Mustang disc/drum master with the proper valve f/r

 

Just what I was thinking.. You need to check your pushrod length and or pedal geometry. I stuck a power booster and master off a 76 Ford PU on my 67 PU. All bolted up and seemed cool. But you had no brakes till the last inch of pedal.
Theres not many boosters that fit in the small space they give you.
Supposedly Geo Metro boosters fit and bolt on. Never did it myself. But I hear it works great, and is a lot cheaper than the boosters sold in the catalogs.
I have a Granada, and a Falcon here. If I remember I'll try to get some measurements.

 

There is no booster, they're manual brakes. The car was originally a 3 spd but I removed the third pedal and shimmed it up so essentially its the stock pedal. Now that it has been brought up, I can recall modifying the pushrod as the one that came with the booster was too long. I bet that's the problem, no brakes until the pedal gets closer to the floor.

Also glad you mentioned your 76 to 67 swap, I am doing one of those this summer on a 72 F100.

 

Just a thought....maybe need to add a residual pressure valve? The calipers may be retracting naturally and a residual valve will keep them (the pads) up against the rotors. Without it you may be moving the pads a fair distance without really applying any clamping force.

Going to a a larger MC will give a higher pedal but with the same pedal pressure the line pressure will be lower making you REALLY push on the pedal.

Not necessarily any definate cure suggested in my comments, just food for thought.

 

RPV's **** and are definatly not needed in this case.

It sounds like you didn't use all of the donor Granada parts you should have. If I read your parts list correctly you left out the combination valve. This valve is there for mulitple reasons and one is to balance out the system. More than likely you are only stopping the car on either the front or rear brakes.

Annother thing that valve does is meter the fluid to the rear brakes. It does a supremely better job at controling the rear brake circut over the proprotioning valve you have.

Next up, make sure the lines are plumbed correctly. The line attached to the master cylinder with the large resevoir goes to the front brakes. Swaping them will engage the brakes in the wrong order and give you a funny feel to the pedal and the brake system.

I would agree with Jerry and Kenny that you may have air still trapped in the system.

With everything as it should and you still have problems you may have a horribly mis-arched set of shoes and drums. It is possible that you need to flex the shoes to gain enough contact area to stop the car. But that is a longshot at best.

 

Did you bench bleed the master cylinder?

Does the pushrod have enough travel to bottom out the m/c when a bleeder screw is open? usually single cylinders have less travel than duals, so maybe it's just not bleeding the master cylinder fully.

Also if one bleeder screw is open, then the pedal should not hit the floor, if it does than the dual m/c is not doing it's job and you might as well have a single in it, or redo the pedal setup so it gets full travel.

 

I agree with ElP. I used a combination valve, from Borgson, and nothing else. That one valve does all the work. No extra proportioning valves or RPV's needed. Works like a new car.-MIKE

 

For what it's worth, I used a 85 mustang 6cyl booster on my 67 mustang, it worked fine. The clearance between the MC and the brace might be tighter on the falcon though, I can measure my booster if you want. I had to drill new mounting holes, and open up the center hole a bit. I used the manual pedal also, I just drilled a new hole through it about a 1 1/2 below the stock pushrod stud, and ran a grade 8 bolt with a steel bushing on it. There was no problems between the booster and the manual mustang MC fitting together. Works fine, the pedal is a little low for my liking, but braking pressure seems fine.

 

one thing to look at (and i might be talking outta my *** here. . . it's been known to happen )

with "99%" of the lines replaced as you said, perhaps there is a short run of old line with a smaller ID?

i'm kinda thinkin outloud here, so someone please correct me if my line of reasoning is flawed, but if you have a line with (and this is just a generic 'frinstance) a 1/4" ID going into a line with a 3/16" ID then BACK into 1/4" . . . perhaps that would be a problem? i know little about fluid dynamics, but common sence says that you are gonna loose a ****load of hydrolic pressure if that would be the case... even if the restriction is as simple as a coupler or a frame p***through to the soft lines...


i hope that if nothing else this gives you something to think about... i'd be interested to know what the guys with more experiance have to say about my logic at any rate

Good luck, and speed safely

 

Some good information, I will look at it more in depth.... I attempted to use the factory combination valve when I did the swap a few years ago but it leaked, the one valve in it was bad and I couldn't find a replacement anywhere, even from Ford... So I simply put some unions in it and ran the system 50/50. It worked OK but not to my liking, so I put in the Wilwood unit in it along with the Line-Loc and it's still the same, will adjustments done with the PPV.

All of the lines were new except for what goes directly to the MC. It's been awhile so I will look at the whole system. Thanks