Hello, i own a '78 Bronco and have replaced every brake componate there is on it. When i push the brakes it is very responsive, but i can push the pedal all the way too the floor with no more braking ability. I have adjusted the rod that goes inside the brake booster to the master cylinder to specs. The first time i adjusted it, i about caught the brakes on fire. Is there any thing i missed on these brakes? How far can i adjust that rod? Please respond, any and all welcome. Thank You in advance. Rob

 

Hi, you can adjust the rod until just before the brakes start to drag you can usually feel when they drag just put it in neuteral while moving and see if it is coasting or if it is trying to stop you will feel it when it comes to a stop. John

 

How do the brakes work other than that? Mine will go to the floor too, but just touching the pedal puts my nose in the windshield! I love it!

Nathan

 

Rob, I've got a similar problem on my '68 F250 w/ power disc/drums. I had replaced every component, save for the power booster, and had awesome brakes. Then on Sat. my booster started hissing so I went and got a remanufactured one and installed it. Now my brakes don't work worth a flip. I've adjusted the booster rod and bled the system several times, all to no avail. I talked with a mechanic and he says it sounds like a master cylinder problem, despite telling him that it is also new and was working properly prior to the new PB install. Since the MC is under warranty, I'm going for a new one tomorrow. If that doesn't work, I just don't know what to do. Let us know if you find a solution and I'll do the same.

Jim

 

Jim, all vaccume boosters are not equal, I saw a great difference when I changed mine. You may be better off trading in that booster.

Nathan

 

Are you guys pulling the rod out of the power booster that goes
to the master cylinder? My manual warns against this. It says
there is some sort of "reaction disc" that can fall out and if
it goes down in the booster you are in trouble. It talks about
the brakes being too sensitive and excessive pedal travel with this disc missing. I figured this is why when I went to advance auto for a power booster, it came with the master cylinder already mounted.

 

Hey Nathan, well the brakes work O.K. they will put the nose down, but i'm kinda affraid if i have to really put my foot in it, its going to the floor. Kinda worries me. Just normal driving around town, stopping at red lights, stop signs, etc. There fine. Just that one sudden suprise stop, you know what i mean. Every thing to do with the brakes is brand new, except the lines and proportioning vavle. I guess what Franklin said mine did'nt come with that disk. I read that also, and when i got my remanufactured brake booster, i did'nt see no disk TO be sure that it was in proper. I guess i'll try to adjust that rod again, the chilton book says to adjust this rod 0.931 To 0.946 Inch, which is a little less than an inch, like 15/16ths. Thats what i adjusted it to. Well, thanks everyone for the replys, i really appreciate it. Please let me know if any more ideas come in too mind. Rob

 

I have found alot af mastercyl. that have different pistons in them almost everyone I replaced I have had to adjust the rod. I don't remove the rod I adjust it in place and I turn it about one turn and try it keep adjustinguntil the brakes feel like they are dragging then back off one turn. I have also gotten a mastercyl. that was a ford rebuilt and it was bad it went to the floor if you stood on the pedal it was under warranty when it was replaced this was the one with the plastic reservoir I fought with them over that until the warranty was done then replaced it myself and the new one I bought worked fine.
John

 

Thanks fatforty, i think i'm going to see if i can find the reciept to my brake booster and master cylinder and try and replace them both. Hopefully i can get one with the master cylinder attached. I've moved recently, so i guess i'll start the search. Thanks to all who responded, many thanks. Rob

 

Hi, it shouldn't be the booster, but sometimes they bore the master cyl. and install new oversize piston but if it is too much the fluid passes by the piston and the pedal goes to the floor on hard brakeing. John

 

Hey guys, I replaced the booster and master cylinder tonight and the new set-up works great. I guess it is just a given that not all remanufactured items are "good." Thank goodness for warranties.

 

I have a 76 f-350 with a similar problem. The first push on the pedal has a lot of travel, but if I pump the pedal once it has great pressure. If I step hard on the brakes before pumping it once, the rear brakes lock up and skid. If I give it a quick pump, the brakes will hardly ever lock up and comes to a good, quick stop. I changed the master cylinder about 2 years ago and have no leaks. I just recently replaces both front hoses and calipers and bled the system several times. I am sure that there is no air in the system, and it doesn't feel spongy, It just has a lot of travel. Has anyone else had a similar problem? Where should I begin?

 

I had the same problem. I replaced the power booster and the vacuum hose for it and the problem was solved.

It should be noted that a bad vacuum leak can cause the brakes to malfunction IF IF IF they are power brakes.

Check the clamp on the vacuum line to your booster to see if it is in good shape.