brake pedal travel

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?

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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Or, thinking about it, the pedal may be all the way down instead of up.

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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?

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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

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!

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!

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

Every 50 year old proportioning valve is 'the next thing ready to ruin your day" (car) !!!!

https://www.musclecarresearch.com/valve-kit-kh

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

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!

This is how I set my pushrod length.

I start out with the push rod too long, and apply hand pressure (no fasteners installed, master cyl loose) to the master cylinder casting pushing it towards the booster.  You can feel when the master cylinder piston starts to move.  Using feeler gauges as spacers between the brake booster and master cylinder casting I try different thickness combos of feeler gauges until I can not feel the piston move when I press the master cylinder casting against the brake booster.  

Scribble down the thickness of the feeler gauge combo.

Figure out what the thread pitch is on the brake pushrod adjuster.  I think it is 5/16-18 or 5/16-24

For example.

Say you need .043" worth of feeler gauges, and the pushrod adjuster is 18 threads per inch

Every full rotation of the adjuster changes its length by 1/TPI .... (1/18tpi in this example)=.056"

So every full rotation is going to change the rod by .056" of an inch with 18 threads per inch adjuster...

.043" (Feeler gauge stack)  + .020" (free play specification) = .063"

Feeler gauge stack + free play specification / distance moved in one rotation = how many turns you need to shorten the rod.

.063"/.056" = 1.125 turns (1 1/8 turns)

So you would take the rod out, mark it with a pen and shorten it by 1 1/8 turns.

Assemble and enjoy perfection.

More examples....

If the adjuster rod is 5/16-24...

1/24= .042" per revolution

If the adjuster rod is 1/4-28...

1/28= .036" per revolution

If the adjuster rod is 1/4-20...

1/20= .050" per revolution

I measure from the flange face of the booster to the end of the pushrod and then from the flange face of the master cylinder to the middle of the piston pocket and get the difference between the two, making sure the pushrod is the shorter of the two.

I'm sorry for wasting people's time I think I'm a complete idiot! I took my reservoir off of the booster, disconnected 2 lines and put that thing in my vise and looked at it. All of a sudden I thought perhaps this is the wrong Master Cylinder for my car with factory disc brakes. Then I took the clip off that holds the cylinder, used a little compressed air and finally got the MC in my hand. Only then did I realize I had installed it backwards  :shootself: :shootself: :shootself:  and because of that no room for the Push rod and super hard pedal.

It's been 3 years since I took my braking system apart and I could swear I followed the installation instructions for the new MC, perhaps they were in chinese.

Now I have working brakes but my pedal goes down and stops at about 2-2.5" before it hits the floor board the pedal feels spongy at all times. Master has been bench bled again and front and rear brakes have been bled as well. 

Question is...Do I need to adjust the push rod in or out? Make it longer or shorter to get rid of the spongy pedal?

Can you send a pic. I am trying to figure out how were you able to install it backwards.

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I think he's referring to the piston.

The entire assembly, including the reservoir, cylinder, piston, and seals, is the master cylinder. A soft pedal is air in the lines or slave cylinders. To much pushrod clearance results in too much pedal travel, too little keeps the piston from fully retracting, not allowing the cylinder to fill with brake fluid, which results in no brake pressure.

I'm sorry for wasting people's time I think I'm a complete idiot! I took my reservoir off of the booster, disconnected 2 lines and put that thing in my vise and looked at it. All of a sudden I thought perhaps this is the wrong Master Cylinder for my car with factory disc brakes. Then I took the clip off that holds the cylinder, used a little compressed air and finally got the MC in my hand. Only then did I realize I had installed it backwards  :shootself: :shootself: :shootself:  and because of that no room for the Push rod and super hard pedal.

It's been 3 years since I took my braking system apart and I could swear I followed the installation instructions for the new MC, perhaps they were in chinese.

Now I have working brakes but my pedal goes down and stops at about 2-2.5" before it hits the floor board the pedal feels spongy at all times. Master has been bench bled again and front and rear brakes have been bled as well. 

Question is...Do I need to adjust the push rod in or out? Make it longer or shorter to get rid of the spongy pedalter you swapped the piston around did you

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Did you end up following the pushrod adjustment suggestion from Don or myself after you swapped around parts in your master cylinder?

Can you send a pic. I am trying to figure out how were you able to install it backwards.

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Here you go, please don't laugh LOL

Can you send a pic. I am trying to figure out how were you able to install it backwards.

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Click to expand...

Here you go, please don't laugh LOL

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I tried combinations of your suggestions and I think I have to adjust the push rod out a little more. I do no think there's any air left in the system though. I'm using DOT 5 silicone brake fluid simply because it won't harm painted surfaces and I went through a whole quart. By the way, the MC WILL fit both ways, but this was the wrong way haha.