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4 wheel manual disc brakes - almost zero brakes

15K views 75 replies 16 participants last post by  patrickstapler 
#1 ·
This is the last issue I need to resolve on my 67. The brakes. Manual, all disc. Was power, but i hated the booster/MC and could not get the booster and MC to function as a system.

Everything is brand new, including hoses.
Front is standard 11" rotors, KH 4 piston calipers, etc.
Rear is SSBC system.
Master cylinder is new, got at local mustang shop, same one that comes with SSBC kits, except it is 1 1/8" bore. Smaller bowl for rears.
Pedal is manual brake pedal.
MC rod to pedal is adjusted.
No brake line loops above the MC level.
Bench bled MC more than once. Tap with mallet, bleed again, etc.
Bled brakes multiple times. Vacuum bled as well.
Rear brakes bypass the stock distribution block. Capped off the rear brake ports in the block. Don't have a brake warning light in car, so capped off that sensor port. Front brakes do go through distribution block.
Proportioning valve installed for rear brakes.
After installing MC, capped off the ports and tested pedal. Pedal barely moved then held rock steady, even after 60 seconds held down.
Went over all the flex/rubber lines (not braided) with pedal held down. No bulging or such.
No leaks after going over entire system. Also had someone else go over system to check for leaks.
Yes, calipers on correct sides. I checked, someone else checked. Unless I was a few beverages deep. Pics below. Of brakes, not beverages.

The issue: Brake pedal is super soft, lots of travel, although doesn't quite bottom out. 4-5" of travel and never really firms up. Barely stops the car, have to really lay on the pedal to slow it down. Full panic stop doesn't lock anything up and my leg hurts with the effort. Pedal doesn't pump up either. No matter how quickly or fast I pump the pedal, it's the same. This is similar to the issue I had with the booster installed, except that would pump up a little. And stopped better, but not much.

Other than getting a pressure gauge to check pressure at 4 corners, any other suggestions on where to start now? I have read dozens of threads on the topic and am still at a loss.
My 65 has the granada fronts, rear drums, and works great. Cobra roadster has SN95 style manual brakes, rock solid. I know how the pedal feels in those cars and this one isn't even close to the same feel.

This is the MC. This is with the caps/plugs in place to check the MC. Pedal was rock hard, no travel.


Front passenger brake caliper during installation.




Front driver side caliper.


I am thinking that there is something in the front brake circuit that is causing an issue. Why? I have replaced the rear disc brakes twice. No change. Could be distribution block? One of the front calipers? Or both calipers? I just don't know what would cause such excessive pedal travel. Feels like to psi is getting to the calipers. Need to find a pressure gauge/setup, perhaps locally!

Perhaps clamping (very softly) the four flex lines and testing pedal as suggested in the tech section of SSBC website.
 
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#6 ·
The bleeder on both front calipers are at the top, slightly pointed towards firewall. In that second pic, I just hadn't installed the bleeder yet. Bled them yesterday, so I am pretty sure on orientation.

Just spoke with SSBC and they recommended removing MC and bleeding it again at a 10 degree angle, then gravity bleed before depressing pedal and possibly sucking sure back into MC.
 
#7 ·
Have you had car on lift and had someone press brakes and checked to make sure you didn't have any rubber lines mushrooming?
Do you have a drum/disc master which still has a residual valve installed?
Has anyone talked to you about Master Cylinder bore size and pedal effort?

FWIW Manual 4 wheel disc in my mustang always felt a little soft....till I put a wilwood master in.
 
#10 ·
The real brakes have an e brake and it is hooked up and functional. Adjusted per SSBC directions.

Yes, I had the car up on stands and had someone apply the brake while I looked for any mushrooming or misshapen rubber flex lines/hoses.

At this point, I probably wouldn't mind if the brake pedal was a little soft. I just want it to stop the car!

There is not residual valve in this master cylinder. I checked. May have to look into a wilwood master in the future.

I read up on bore size and pedal effort. Lots of info on this site. Once I have a working system, I can make a call on changing the MC to a different bore if I don't like this one.

The MC/pedal rod was adjusted to the pedal height I wanted. I can pull it back a couple inches (MC doesn't have clip groove), but rod can't fall out either. Pedal has full travel. It engages the MC within half an inch I believe. All very similar to my 65.

If it's air, then the MC or the front calipers will be the first place I'll be looking.

SSBC also did suggest clamping flex lines at four corners to help is isolating the issue. I have flat clamps, just has to be SUPER light pressure, don't want to damage the hoses.
 
#11 · (Edited)
1-1/8" mc is WAY too big ! A 15/16" would be WAY better and you wouldnt need to push the pedal with both legs. Long long ago I also tried the 1-1/8" and I need at least 2 legs. A 15/16" works perfect. My station wagon in foto had 4 wheel disc and a 7/8" MC and NO booster and stopped like it had a power booster. Another thing I found was Porterfield R-4S pads work great on the street and add to the quicker stopping.
 

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#13 · (Edited)
Cross-over tubes are found the top of the small calipers. That's the only place they are on a
65/66 caliper installation. They connect the top inner to the top outer half. Yours are wrong.
(at least in the bottom-most picture)
1" is the correct master cylinder bore size for what you've got. 1" is also correct for use
with the 65-67 big Galaxie front calipers and the SSB rear disc setups.
Bench bleeding doesn't guarantee squat. We never bench bled ANYTHING at JBA or at
GW.

You have to have air in your system.

ex-Global West GM
1991-1995
 
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#15 ·
I'll take a look at the cross over on that front caliper. That was the way it came, but perhaps something goofy (me) happened to it.
 
#16 ·
I can see that the calipers have the "bosses" or "ears" cast in them so that the crossover tube can be installed high or low. Are all 4 of those bosses/ears drilled and tapped for the crossover tube fittings? If all 4 are drilled and tapped 2 of them will have plugs in them.
 
#20 ·
I checked them today. The two front calipers both have the crossover on the top, bleeders at the top. Both calipers are oriented the same. That picture was probably taken before fully assembled.

Bummer, thought I had found the issue.
 
#22 ·
It's not the master cylinder you'd be concerned with having latent
air in it, it's the whole rest of the system.

ex-Global West GM
1991-1995
 
#25 ·
And I am not sure where there would be any air in the remainder of the system at this point. Any suggestions?
 
#30 ·
Where does the brake pedal "engage" when you step on it? With an 1 1/8" master you should be getting
a pretty darn hard pedal after about a 1-inch pedal depression even with rubber brake hoses. If you're
getting not a lot of pedal resistance and it's going all the way to the floor, you've got hidden air in the
system or the master cylinder is jacked up.

Try this test for any air lurking in the system-
pump up the pedal 3-4 times pretty much normally and not frantic.
On the last pedal push, leave the pedal down, with your foot on the edge.
Slide your foot sideways off the pedal, letting it spring back up toward the
dash and have someone observe the fluid level in the master cylinder for a
geyser. If you see something more than very slight ripple, there is air in
that brake circuit. (obviously protect the paint and eyes, etc)

ex-Global West GM
1991-1995
 
#27 ·
Yes, that will be one oft next steps, to isolate the circuits. Hopefully will have time today or tomorrow to try this out. Still need to bleed the system since I just got the MC back on.
 
#28 ·
I'm still stuck on the rear brakes (as that's where I had my own troubles ...).
What if you apply the e-brake (to remove any clearance between pads and rotors on the rear calipers),and apply the brakes ? Any change ?
DannyG
 
#31 ·
It shouldn't make any difference. SSB uses a generic rear caliper design based upon Ford's design.
I bled mine and the parking brake cable wasn't yet hooked up.

This SSB kit had a "factory" located bleed fitting that isn't used and the primary bleed fitting was on the
banjo bolt. Don't know if it would bleed successfully without the banjo bleeder as I didn't try.

ex-Global West GM
1991-1995
 

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#29 ·
Here is the driver side caliper, so front of car is to the left.

Crossover installed.

 
#32 ·
The 1-1/8" bore master cylinder shouldn't be the issue. That is sized about right. I fear your problem stems from the fact that the system USED to be power brakes and you didn't change brake pedals. The attachment point for the master cylinder pushrod sacrifices mechanical advantage for stroke since the booster provides an assist.

The second part of your problem is most likely related to adjustment of the rear calipers. You should rotate the piston CCW 1/2 turn at a time until you can no longer slide the caliper over the pads, then back 1/2 turn. Excessive piston travel will result in too much brake pedal travel.

Last, but not least, check your pushrod adjustment. A pushrod that won't allow the master cylinder piunger to return all the way will result in fluid (and air) being trapped in the circuit and never able to make its way back to the reservoir.
 
#34 ·
Brake pedal is a manual brake pedal.
Push rod allows full travel of master. It fully allows the plunger to return. The rod is not clipped into the plunger right now, meaning I can pull the pedal back and the rod will slide out.

The pedal currently doesn't really engage at all. It goes almost the full travel of the MC, pedal moves a good 4-5" before there is any feeling of pressure. I agree that with this bore size, I should be getting a hard pedal pretty quickly. Currently it is the opposite.

bartl, my rear calipers don't have screw calipers if you are referring to the el dorado style. I'll check though tonight to see how tight they are to the rotors. Last time, there were pretty tight up against them.
 
G
#40 · (Edited)
bartl, my rear calipers don't have screw calipers if you are referring to the el dorado style. I'll check though tonight to see how tight they are to the rotors. Last time, there were pretty tight up against them.
Brian, there are two basic designs of rear calipers in regards to the emergency brake. If the caliper has nothing associated with it, then there is a "hat" style rotor and a tiny drum brake system that operates the emergency brake. If no "hat" is there, then the caliper must operate in two ways, hydraulically and mechanically. First is the hydraulic fluid, pushing the piston out,ever so slightly. This also can activate the threaded portion if moved far enough. The second function is the piston moving out by way of mechanical means. This usually involves the threaded portion, which retracts when the parking brake is released. It has have these motions separate from each other, so bother will operate correctly, but there is some crossover in that the piston can move only so far before it will have to thread it self out. Since the piston barely moves during braking, this motion seldom happens.

 
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