77 brake issue

[jeffncs]

Here’s my situation….
1970 bronco with a 77 D44 and 77 disc brakes up front and stock drums out back. Everything is new on it including the m/c, booster, lines, calipers….everything.

I have to just about STAND on the brakes to stop. Wife won’t drive it. Is it possible I have the wrong m/c or distribution block? I’m legit pushing the pedal to the floor.

No air in the lines; firm pedal.

I’m not opposed to just changing the m/c and distribution block - do you have a local parts house part number I can request?

Thanks much!!

 

[B RON CO]

Hi, a rock hard brake pedal is a sign of a faulty power brake booster. Does your engine produce enough vacuum? Good luck

 

[jeffncs]

Hi, a rock hard brake pedal is a sign of a faulty power brake booster. Does your engine produce enough vacuum? Good luck

As clarificatio, the pedal “feel” is normal. However, I have to push the pedal to the floor to stop...all the way to the floor.

 

[serial car restorer]

Something isn't right. Pedal should not go to the floor. Maybe 3-4" travel if everything is correct. I doubt the prop valve is at fault. I'm wondering if the pushrod length is correct.

 

[ksagis]

3 to 4 inches seems like way more than I would consider acceptable.

Agree with @serial car restorer to check push rod gap and also that MC bore is matched to rest of system.

 

[serial car restorer]

3 to 4 inches seems like way more than I would consider acceptable.

I should have said 3-4" at most in a full on panic stop. Normal braking should be a lot less.

 

[Apogee]

Sounds exactly like when the booster failed on my '77 EB...high, firm pedal with almost zero brake torque. Test the booster by pumping the pedal several times to evacuate the vacuum from the booster (or remove and reinstall the check valve from the grommet on the booster), apply the brakes with moderate force, start the engine and note the amount that the pedal drops. If the pedal drops an additional .75" to 1.5", then the booster is most likely functioning like it should.

How much vacuum do you have at warm idle? I'm assuming you would have said something if this issue coincided with an engine or cam swap, but it never hurts to ask.

 

[jeffncs]

Well…. It was the booster. I threw a spare booster from my stash onto the truck last night and it works perfectly now.

I guess I’ll have to use that Astro van hydro boost on my truck..,,darn.

 

[DC_Gearhead]

What are the chances you put your front calipers on backwards? I ask because I did it. The bleeder should be on top with hose at bottom. I had the same symptoms. It was because the air was trapped and couldn’t go up to get out of the bleeder. Basically a big pocket of air was trapped.

Another thing to check is your plumbing. Make sure front and rear are to the correct chambers on your master.


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