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brake pedal travel
#1
runninpony 
Hi All, My brake booster is back in and I have zero travel on the brake pedal! It's Rock Hard! Now would that be normal since I have no vacuum to it (engine uninstalled). Brake fluid reservoir is full and have not been bled yet. Should I try to bleed the brake lines?

71-73 Mustangs never die, they just go faster!
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#2
You should still have travel without vacuum but have to push harder. I have a new booster in and was able to push the pedal to bleed the brakes. Not bleeding shouldnt hinder you from pushing so if i have to guess something is jaming the pedal hindering its travel or in the booster.

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        [Image: 20160929_171923_edit2_small.jpg]

1971 M-Code Mach 1 w/Ram Air, 408 stroker, 285/291 0.558" roller cam, Blue Thunder intake, TKO600, Hooker headers with electric cut-offs, FiTech EFI w/ RobBMC PowerSurge pump
Strange center section with Truetrac, 3.5 gear and 31 spline axles, 4-wheel disc brakes
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#3
Or, thinking about it, the pedal may be all the way down instead of up.

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        [Image: 20160929_171923_edit2_small.jpg]

1971 M-Code Mach 1 w/Ram Air, 408 stroker, 285/291 0.558" roller cam, Blue Thunder intake, TKO600, Hooker headers with electric cut-offs, FiTech EFI w/ RobBMC PowerSurge pump
Strange center section with Truetrac, 3.5 gear and 31 spline axles, 4-wheel disc brakes
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#4
(07-23-2018, 06:57 PM)NOT A T5 Wrote: Hi All, My brake booster is back in and I have zero travel on the brake pedal! It's Rock Hard! Now would that be normal since I have no vacuum to it (engine uninstalled). Brake fluid reservoir is full and have not been bled yet. Should I try to bleed the brake lines?

Your pedal should have an inch or two of travel before it gets hard
Check that you have adjusted the pushrod between booster and master cylinder correctly, if too long will get a hard pedal and brakes will come on too quickly, probably drag as well, too short and pedal will be close to the floor
Been posted here before but basically need to get a clearance of about 20 thou between the master cylinder piston and booster pushrod, hope this helps


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#5
runninpony 
Thanks, I will try to bleed everything and if that doesn't help I'll take the master off to check the push rod gap. I thought the guys who rebuilt my booster would've adjusted the gap to where it should be. I should've double checked it BEFORE I put everything back together!

71-73 Mustangs never die, they just go faster!
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#6
runninpony 
Hi Guys! Talked to Booster Dewey they said push rod was set to Ford spec and when I took of the reservoir (with all lines still attached) I noticed the end of the push rod sticking out about 3/4". So I pulled out the push rod/piston and adjusted it to make it the shortest length (about 3/8" shorter than before) and re-installed everything. Now I have about 2" of pedal travel and was able to bleed my brakes after installing brake speed bleeders (they work real well) but still when I pump my pedal it won't get hard. I have about 22" of vacuum from the engine (just cranking) and everything looks good and no leaks. I pumped the pedal like 50 times and it stays the same! Of course I bench bled the master cylinder, all new stainless steel lines. Could it be my proportioning/distribution block since the brake warning dummy light is on? But if this piston in the distribution block is off center why do I get fluid out of my bleeders!? I checked the brake switch and it works fine. Sorry for all the questions, I just don't know what else I could do!

I even drove the car for about 10 feet and slammed on the brakes, to no avail. There's slight drag on both front wheels when spun by hand. No drag on rear wheels.

Thanks in advance!

71-73 Mustangs never die, they just go faster!
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#7
Could be a few things but firstly if you have taken 3/8" out of the adjustment it may have been too much and will give you a lower pedal with less brake force.

I had to adjust mine twice to get it to where I was happy with it and only needed to make small adjustments to make a big difference i.e. 1/16" as the required gap between pushrod and m/cylinder piston is only 20 thou. Mine not being the original setup I couldn't advise how far the pushrod would stick out so perhaps another member can help with this otherwise you will need to remove the master cylinder again and take some accurate measurements with a vernier caliper.

For example if your master cylinder piston depth is 0.300" and is flush with the mounting face then desired pushrod stick out is 0.280" however if your piston protrudes out of the cylinder for example 0.050" then you will need to subtract this from the above which would give a pushrod stick out of 0.230"

Where I went wrong is the Falcon master cylinder needs to be preloaded before measuring this but don't believe the Mustang one needs this.
There could still be other issues others can help with but I would first establish correct pushrod length to eliminate other causes
Good luck with it
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#8
Every 50 year old proportioning valve is 'the next thing ready to ruin your day" (car) !!!!


https://www.musclecarresearch.com/valve-kit-kh
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#9
It is a demanding adjustment, you only have a .015" range for proper brake operation. Ideal is just making contact when the MC is bolted down. Max MC piston movement is .015. More than that and the brakes will drag, slack will cause excessive pedal movement and poor braking. The Ford service manual describes how to make a gauge to set it. Chuck
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#10
runninpony 
Thanks everybody for their input! I do have the shop manual. I just can't see where I can get it to adjust to the .020" gap between the push rod and the master. 
Also, in the manual, there are 2 schematics of the distribution block, one for "light car" and one for "custom car" where the lines are hooked up differently. I find that odd! Well, I guess I'll take the reservoir/master off again without disturbing the brake line connections. Before I was messing with the push rod length the push rod touched the master almost immediately when I tried to install the reservoir onto the push rod to get it mounted to the booster (with where it was set to Ford spec) so I thought the push rod was sticking way out, that's why I made the adjustment. Thanks again guys, you're very helpful!

71-73 Mustangs never die, they just go faster!
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