SSBC power front disc vacuum booster issue - Ford Mustang Forum
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post #1 of 27 (permalink) Old 07-25-2017 Thread Starter
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SSBC power front disc vacuum booster and MC issue

My new to me 1966 Mustang 2+2 has been modified to a SSBC power front disc brake kit and OEM drum rears. The brake pedal goes nearly to the floor if you pump the brake with the engine off and the vacuum bleeds off as you pump.

The problem is the pedal doesn't automatically return to a full height pedal once you start the car. I have 18 psi vacuum at idle so the booster is getting plenty of vacuum. I tested the vacuum booster by pulling the vacuum check valve out and found the booster still had vacuum in it after 3 hours with the engine off so it shouldn't be leaking.

If I reach down and pull the pedal up with the engine running, it returns with a small pop to a full pedal and the brakes function normally again. So someone help me explain what is happening. It's as if the booster diaphragm bottoms out once the vacuum is gone and doesn't return to normal until you pull the pedal up. I'm assuming the problem is just in the booster and not the MC. What's wrong and what would you replace? Thanks.


1966 Mustang 2+2, A code, AOD AT, PS, PDB, AC, Pony deluxe interior

Last edited by poqman; 12-17-2017 at 08:00 PM.
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post #2 of 27 (permalink) Old 07-25-2017
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suggestion

Be sure there is no "gunk" build up in the master cylinder or brake lines.

If your "push rod" from the booster to the Master cylinder is too short it will cause excessive brake pedal travel. Too long, might cause the Push rod to go into master cylinder too far and not "release" there by not let the brake pedal return to normal position.
This video will explain what I am speaking about. Make small adjustment, in 1/2 to 1 turn,,,,, small amount of travel here makes a big difference. This is just a suggestion and may may not be the cause of your problem.


Hope this helps,
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post #3 of 27 (permalink) Old 12-16-2017 Thread Starter
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Just a follow up. The brake pedal not returning had continued for the past 5 months so I decided to contact SSBC and have them send me a replacement vacuum booster and master cylinder. I never felt anyone else could drive the car while having to use your left foot to pop up the pedal after each braking, but otherwise the brakes felt normal.

Now I'm having the same problem that so many others have documented about our vintage car brakes. The new parts are installed and I have about 2-1/2" of dead pedal at top and then the pedal is solid and stops the car if you push hard enough without the feeling of the power booster assist. SSBC says it HAS to be air in the lines and not a faulty MC. I've bench bleed the MC and gravity bled the brakes as SSBC recommended 3 times, then tried to vacuum bleed the system and finally paid for a pressure bleed in desperation. The results have had no change. I also make sure the booster rod and MC had a .000 - .015" clearance and that the rear drum brakes were adjusted. All those who have documented this problem on blog sites never posted a solution, just theories. Many bloggers said they installed an entire SSBC brake kit and still had this problem using all new parts. I've got the MC out of the car and sitting in the vise for another bench bleed wondering what to do next. So sad I can't use the car until I can find a solution. If you have ideas, I'm open to try something different. I'm thinking about replacing all the rubber brake lines and the proportioning valve just because I don't know anything better to try.
One note, I was always unhappy with the gravity bleed of the rear brakes. They took as long as an hour to bleed an ounce from each wheel eventually stopping. I don't understand why.

1966 Mustang 2+2, A code, AOD AT, PS, PDB, AC, Pony deluxe interior
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post #4 of 27 (permalink) Old 12-16-2017
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Well, IMHO, it's time to scrap the SSBC system.....and try the oem disc brakes that are every bit as good as most of the aftermarket.

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post #5 of 27 (permalink) Old 12-17-2017
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I agree that you should just get rid of the SSBC system. I bought one of their power brake upgrade kits for my '66, and never got it to work properly (don't recall the symptoms). The same story with their rear disc brake kit, although I do recall the reason there: no way to hook up the parking brake cables. And their technical support is just about worthless.
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post #6 of 27 (permalink) Old 12-17-2017
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OK, so what do you know about your rubber brake line connections? Hopefully not original at this point!
I can tell you, insuring the flexible hoses are in good shape does make a difference in the over all performance.

I, for one, would not want to scrap a $300-400 brake booster without a bitter fight to the end. Perhaps, someone will way end with a known good setup to compare. Regardless the mfg., generally, all work the same.
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post #7 of 27 (permalink) Old 12-17-2017
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I converted our OEM single cylinder, power brakes to a dual cylinder master cyl, and had a terrible time bleeding the new master cyl.

I finally got it bled by clamping the master in a vise using one of the mounting tabs. BUT, I "rolled" the master cyl in the vice so the output ports were higher. With the master clamped with the rear towards me, I tipped or rolled it clockwise as far as I could without spilling brake fluid out the lower side. This put the output ports a little higher, and the air bubbles came to the high side - nearest the output ports. I had bled the master 3 times and after I rolled the master in the vise, I got more bubbles out.

Now I am not trying to insult your intelligence here, but I am assuming you have little hoses connected to the output ports, and they are putting the fluid back into the reservoir? And you are using a big push rod or big screw driver to push on the back of the master cyl. and pumping many times?

Hope this helps. Dave

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post #8 of 27 (permalink) Old 12-17-2017 Thread Starter
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Quote:
Originally Posted by kenash View Post
OK, so what do you know about your rubber brake line connections? Hopefully not original at this point!
I can tell you, insuring the flexible hoses are in good shape does make a difference in the over all performance.

I, for one, would not want to scrap a $300-400 brake booster without a bitter fight to the end. Perhaps, someone will way end with a known good setup to compare. Regardless the mfg., generally, all work the same.
I too am reluctant to throw away everything and start over, but it's not off the table. But what system comes with a guarantee? As best I can tell, the rubber hoses were installed in 2009. I hear that 6 years is the life of rubber parts, but it seems everyone goes longer. I plan to remove a front hose and check it for condition and blockages. If I find any indication of deterioration I will replace them all.

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post #9 of 27 (permalink) Old 12-17-2017 Thread Starter
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Quote:
Originally Posted by 1carguy View Post
I converted our OEM single cylinder, power brakes to a dual cylinder master cyl, and had a terrible time bleeding the new master cyl.

I finally got it bled by clamping the master in a vise using one of the mounting tabs. BUT, I "rolled" the master cyl in the vice so the output ports were higher. With the master clamped with the rear towards me, I tipped or rolled it clockwise as far as I could without spilling brake fluid out the lower side. This put the output ports a little higher, and the air bubbles came to the high side - nearest the output ports. I had bled the master 3 times and after I rolled the master in the vise, I got more bubbles out.

Now I am not trying to insult your intelligence here, but I am assuming you have little hoses connected to the output ports, and they are putting the fluid back into the reservoir? And you are using a big push rod or big screw driver to push on the back of the master cyl. and pumping many times?

Hope this helps. Dave
I followed their Tech support instructions. SSBC instructions were to bench bleed using a bleeder kit, then tilt down the front of the MC 10 - 15 degrees, use a rubber mallet to tap the front to release the air that clings to the new metal of the MC, then pump some more to dispel any air that dislodged. I did in fact get a little more air. They then instructed to move the MC to the car leaving the MC bleeder kit installed, then remove one bleeder at a time and quickly install the steel line. They only recommend gravity bleeding the wheel cylinders. Since my gravity bleed is so poor, I am going to start looking for brake hose blockages. BTW, I have done this 8 times. This is why the MC is sitting in the vise. I have to try something else because I can't imagine trial 9 will result in another outcome. Removing the hoses and blowing out the steel brake lines would eliminate the possibility of debris in the system and then sealing the system with new rubber hoses. If that doesn't guarantee success the next bleeding then I don't know what will. Does this sound like a rational plan? What about the proportioning valve?

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Gravity bleeding never did a darn thing for me either. Always just did it with the two person method. Usually a kid in the car, and you on the bleeder with a wrench, going "UP!" (up!) "Down!" (down!) and getting brake fluid in various bodily orifices it was never intended to go.

These days, they make some pretty cool little one-way bleeder thingies you can hook up, and not just spray brake fluid everywhere, by the way. Maybe I'm just a traditionalist. Maybe I've got too much brake fluid in my brain?

I'd worry about the valve after you get the air out of the rest of the system. It's probably why they suggest gravity bleed, but you could probably 'drip bleed' those things a hundred times and still have spongy brakes.
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I know you have bled them repeatedly, but your issue still screams of air in the lines/master. I have had cars that fought me like no other. The method I like, is to take a clean, dry clear water bottle and a length of vac line. Put about an inch of brake fluid in the water bottle. When you crack open your bleeder valve, put one end of the hose in the water bottle (make sure the end is submerged in fluid so it doesn't suck air when you release the brake pedal) and the other end on the now-dripping bleeder valve. Press and release the pedal until the water bottle is near full. Make sure the master never runs out of fluid as well. I usually do this two or three times, starting at the wheel furthest from the master, and working my way closer. This method hasn't failed me yet, and you can do it by yourself.

- Scooter
1968 Mustang. 351w, T-5 Five Speed, 8.8, 3.73 trac lock rear end. Power, four wheel disc brakes, (CSRP up front, 8.8 discs out back) Shelby Drop...
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Also... Keep a wrench handy and every time you walk by the master cylinder or refill it, give it a few dozen taps, to move the air bubbles around. Good luck!

Side note: If you ever do decide to dump your brake kit, CSRP makes an oem type kit, that is very well made, and his customer service has been great for me.

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post #13 of 27 (permalink) Old 12-29-2017 Thread Starter
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Thanks for your interest. I agree there must still be air. I've tried gravity bleed, vacuum bleed, pressure bleed and the two person push the pedal as the bleeder is cracked open. I haven't tried your method, but will have to give it a try once the temperature gets warmer. I have gotten a solid pedal, but not great feeling brakes. The top 1-1/2" does nothing, then the vacuum boost is felt helping and the brakes start engaging. By the time the pedal is solid and about 2" off the floor, it doesn't have much power assist and you just have to push hard to stop.

FYI for those gravity bleeding and getting poor or no flow from the rear. I had to break the fittings at the proportioning valve (PV) to get flow again to the rear brakes. I'm not sure if it had created an air lock, but I had hardly any gravity flow to the rear until I bled the PV fittings. I tried gravity bleeding with the PV fully open and 50% closed. Once I had flow again, the position of the PV didn't seem to affect the gravity flow.

1966 Mustang 2+2, A code, AOD AT, PS, PDB, AC, Pony deluxe interior
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post #14 of 27 (permalink) Old 01-11-2018 Thread Starter
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I'm still looking for that BB size bubble of air hiding in my brake system somewhere. I'm literally touching every component and trying to figure if air could be hiding in it. Which brings me to the distribution block. Since my Mustang has the SSBC front disk brake/rear drum conversion kit, the plumbing has been changed from factory. The MC rear brake reservoir goes directly to the proportioning valve and then to the rear brakes. (Note: I had to break the fittings on the proportioning valve before I could get a gravity bleed to the rear wheel cylinders.) The front disk brake reservoir goes to a distribution block where 3 of 4 plugs are used and one is capped. One inlet goes from the MC and then two outputs to the left and right caliper. So my question is what's inside the distribution block? Is there a piston like in a proportioning valve that could be hiding air inside to the plugged outlet? Could this block be replaced by a simple T block?
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1966 Mustang 2+2, A code, AOD AT, PS, PDB, AC, Pony deluxe interior
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I chased around a similar issue, only to find that my pedal pushrod was too short. Adjusted it longer, and it worked great. With the adjustable one, you can just take a piece of 3/8" threaded rod and cut it to the right length and screw it in. I had adjusted mine to the point of nearly falling out, hence the need for the threaded rod.

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