Hello

[Scott Curry]

Newbie here. 1966 candyapple red convertible owned since 1989 and a 1969 candyapple red Mach 1 in restoration, owned since 2014 I will jump right into the forum with a problem I'm having with my 1969 Mach 1. The previous owner had started the restoration on the Mach 1 but threw in the towel on it. I picked it up in 2014 and have continued the restoration. Drivetrain, paint and assembly are completed on the car. Only thing left is the interior and a few trim pieces for the body. The problem I'm having is with the brakes. The previous owner installed what appears to be a front disk power brake kit from Master Power brakes. I installed the stock 1969 distribution block/proportioning valve and attached the lines. I also bench bled the MC prior to hooking it all up. My father and I then bled the system starting at the right rear and working our way closer to the MC. The car had good pedal but after pumping it a few more times it became hard and I lost brakes at the left front wheel. We bled the system again and came out with the same result. The car was not running nor was the booster plugged into the intake. I installed the vacuum line to the intake and started the car. at that point I had a hard pedal that hardly traveled 1 inch. Also while bleeding I noticed that the top end of the pedal activated the rear brakes and the bottom of the pedal activated the front brakes. That seemed backwards to be. All the hard lines were installed to the distribution block according to the diagram in the shop manual. as was the MC hard lines. would this be a problem with the booster or the distribution block? and guidance would be appreciated

Thanks
Scott

 

[tarafied1]

Welcome to the nut house! Sounds like some cool rides. We love pictures!
Since this place is a small group I imagine most will read your post but the question might get more attention in the tech section instead of the newbie intro section. But after saying that we don't follow our own rules and often get sidetracked or derailed anyway so why not here!?!
I'm not a brake expert but in troubleshooting I guess I have a few questions for you. You said the left front brake was not responding when bleeding or after pumping the pedal without boost. Then you said after hooking up the booster and starting the engine again, the left front brake still didn't work? Do I understand that right? Also you mention top end and bottom of pedal activating the front and rear differently, how are you checking that? I'm guessing you mean as you apply pressure the rear brakes activate first and as the pedal continues down the front brakes start to work?
Typically the pedal would apply "pressure" to all four wheels together/equally but the proportioning valve or MC should have a restriction for the rear brakes that allows pressure to build more slowly after a certain point. There is a built-in metering valve that allows the drums to activate just before the disc brakes. This allows the car to settle evenly under braking instead of nose diving. It's important to understand if you have a disc/drum or drum/drum proportioning valve & distribution block and which MC you have because the disc brakes require more pressure than drum brakes. Some MC's will have this restriction built-in.For example, drum/drum MC's have this built in. Some disc/drum MCs do and some don't. (Disc/disc MC's do not typically have any restriction or residual pressure valve).
Drum brakes use a 10lb. residual pressure valve. I've seen the distribution blocks that have a residual pressure valve bolted to them. Some Mustangs/Cougars had the residual pressure valve located at the rear of the car where the hard line goes to soft line by the rear axle.
Anyway, if you have a problem with one front brake not working and a delay in the other front brake (or with the rear drums locking up first), your issue may be in the proportioning valve or distribution block. Maybe some rust or crud in the passage to the front brakes.

 

[Scott Curry]

Thanks for a response. after bleeding the brakes the left front would work but when I press the pedal a time or two more the pedal gets hard and the left front stops working. with or without boost. when bleeding the brakes i noticed that the back brakes were catching first when pressing the pedal. makes it difficult to bleed the front brakes. The distribution block ive installed has the proportioning valve attached to it with hard lines. I do have another distribution block that has the valve built into the block that was purchased at CJ Pony. I will prolly end up trying that soon. I was also concerned about the booster not seeming to work either. with the car running and vacuum hooked up to the booster I still have a hard pedal that will only travel maybe an inch.

 

[tarafied1]

Well typically if there is air in the system the pedal will get harder if you pump up the brakes but often will start to settle down if you hold it for a bit. The rear brakes catching first shouldn't be an issue for bleeding the brakes. When you open the bleeder for the wheel you are working on it won't matter that the other three are under pressure. What is your method of bleeding the brakes? I've seen many pump up the pedal two to three times and hold it while opening the bleeder, of course waiting until the the bleeder is closed before letting the pedal return. This is how I do it as well. I personally have never tried the gravity feed method where you open all the bleeders and let the flow force the air out but I understand that works as well.
I am guessing since it is a Mach 1 that it had Power disc brakes originally? I just ask because you have an power brake kit installed. The power brake pedal has less leverage than the manual brake pedal and a manual pedal with a booster might give you too much pedal pressure making it feel too hard?
So anyway, I would systematically work thru the problems. Try to figure out why the left front stops working, maybe still air in the system or defective caliper or... then I would drive the car. The rear catching first is okay if not excessive. If they lock up then still something wrong with the proportioning pressure. The pedal travel might be normal with your setup. I have a 69 wagon that has really sensitive brakes. When moving slow it will throw you thru the windshield if you jam them too hard but on the road they feel great. I changed the booster and it behaves the same way. If I disconnect the booster I have to press really hard but the sensitivity is the same so the brakes are just touchy!

 

[Scott Curry]

Thanks for the reply. Ive been bleeding the brakes by pumping them up and someone cracking the bleeder while I hold the pedal. Ive tried the gravity bleed as well but seemed to have a better feeling by pumping them up. I will try bleeding them again and try to work the problem out.

Thanks
Scott

 

[tarafied1]

good luck, let us know how it goes

 

[Horseplay]

I had the roughest time ever getting the brakes right on my car. When I finally got things correct and bled them I did it alone with what I feel is the best/easiest method I know. Get a soft vacuum hose that will fit tightly on your brake bleeder. Get a fluid container that is stable enough to sit on the ground upright, fill it with a few inches of brake fluid and let the other end of the "bleeder hose" route into the container with the open end coiled around the bottom so that it will stay there, fully submerged. Then just crack the bleeder and slowly press the brake pedal, let it slowly rise and keep repeating until you feel you have allowed enough fluid to flow through to flush out any air. Tighten the bleeder and move on to the next wheel. Obviously, you start at the wheel with the longest line path and work forward. Its important to keep an eye on your fluid level at the master as this method will use a fair amount of fluid. If you have a helper who can watch for the air bubbles to stop showing it can go a bit faster. This works SO MUCH BETTER than having a helper at the bleeder trying to open and close it as you pump the brake pedal. It is very much like using a power bleeder tool. Only catch is you have to be 100% certain to keep that hose end submerged so you don't pull any air back into the lines.

 

[Grabber70Mach]

I've had to unbolt and tilt the caliper on 69-70's before because of poor placement of the bleeder valve. You must keep the pads in contact with the rotors though so you don't shoot the piston out of the caliper.




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