I have a 77 2wd w/ power brakes. I just replaced the master cylinder, bled everything, and I got good solid brakes now, but the pedal practically goes to the floor before I get any stopping power. Once it gets there, it is solid, it doesn't drift down (which I had with my bad master cylinder).

If I had to guess, I would say that the pedal goes 3/4ths of its total travel before the brakes engage. The Vacuum assist is working fine.

Any ideas?

thanks

ackus

One more thing.....I also braked hard in reverse several times to make sure the drums were adjusted, and it did not help.

 

[updated:LAST EDITED ON 01-14-03 AT 06:47 AM (EST)]Sounds like you've got the air out (the pedal is solid) but there is too much travel. Sometimes the automatic adjusters don't work as well as they should. You might have to adjust the rears a little tighter by hand. Also, if your front wheel bearings are a little loose, the play in the rotor could cause increased pedal travel but that is pretty rare. Snug the rears tighter first and see what it does.
Another thing could be that the rod from the booster to the master cylinder isn't adjusted correctly.
Hope this helps.
Greg

'77 F-250 Camper Special 400ci driver
'76 F-250 Supercab 360ci current project
'71 Mach I 429CJ in storage
'79 F-150 for parts
HONK if you love peace and quiet!

 

I adjusted the rear brakes, and it did not help. I noticed when I changed out the master cylinder a few weeks agothat the rod that runs from the piston in the master cylinder to the vacuum booster was a 2 part affair with one piece (the outer piece) having splines cut into the end that the inner piece screw into. The inner piece is threaded (obviously) and has a domed bolt cap type setup on the end that engages the master cylinder piston.

Is that where I make the adjustment? I did not notice any sort of locking mechanism.....

Just want to double check before I start playing.

One other thing...in the Haynes manual, on the section on bleeding the brakes. It talks about a "bleeder rod that needs to be released to allow fluid to run the front calipers" So I follow the procedure and use a pair of vise grips to pull it out (per the instructions for vehicles under 6800GVW), and it actually PREVENTED fluid from running out to the front calipers. I did not do anything with this bleeder rod when I did the back section, and I got air bubbles and eventually new fluid. When I tried to bleed the front, When I had the rod pulled out it would not bleed but when I released the rod, I for all the air and old fluid out.

Were the people who wrote the manual blitzed out of their mind when they wrote that or is this a symptom of another problem with my brake system. Am I missing something? BTW the brakes were replaced all the way around, new calipers and rear cylinders about 3 years ago.

ackus

 

>I adjusted the rear brakes, and it did not help. I noticed
>when I changed out the master cylinder a few weeks agothat
>the rod that runs from the piston in the master cylinder to
>the vacuum booster was a 2 part affair with one piece (the
>outer piece) having splines cut into the end that the inner
>piece screw into. The inner piece is threaded (obviously)
>and has a domed bolt cap type setup on the end that engages
>the master cylinder piston.
>
>Is that where I make the adjustment? I did not notice any
>sort of locking mechanism.....
>
>Just want to double check before I start playing.
>

Yup, that's the adjustment. The threads are an interference fit. You have to be very careful when adjusting it 'cuz the bleed ports are critical in how the master cyl. operates. Too tight (long) and the brakes won't release or may not even get fluid to pump up. Too short and the fluid bleeds off before you get anough travel to apply the brakes. That's why a lot of people replace the booster and cylinder as a matched pair. Not saying it can't be done, just be careful and make sure of what you've got.
Hope this helps.
Greg

'77 F-250 Camper Special 400ci driver
'76 F-250 Supercab 360ci current project
'71 Mach I 429CJ in storage
'79 F-150 for parts
huct on foniks wurkt fer me

 

hmmm I think I understand what you are saying...one thing I noticed is if I double pump the brakes, I get the grab sooner the second time compared to the first....so I am thinking that coincides with the "too short" scenario.

Am I understanding this correctly?

 

Yup. Either that or if there is still too much travel in the brakes somewhere it will do the same thing.

'77 F-250 Camper Special 400ci driver
'76 F-250 Supercab 360ci current project
'71 Mach I 429CJ in storage
'79 F-150 for parts
huct on foniks wurkt fer me