It all started about two days ago while out on a normal drive. I hit the brakes and they went almost all the way to the floor before they engaged and the brake light came on. I pumped them for a minute and it got a little better but not normal by any means. I pulled over and checked for leaks and there were none I could see. Checked the master cylinder and it was full as can be. I haven't changed my shoes and pads in a while so I thought I just needed to replace them. I thought it was a little strange that they would just go all of a sudden but I had been hauling some pretty heavy loads of wood latley so I thought maybe that was just the final straw.
So today I finally got it up on a lift and went to work. New pads, rotors and shoes and drums in the rear. I attempted to bleed the lines but even with the aid of penetrating oil the bleeder fittings would not budge. I was afraid to crank them too much because of past experiances with breaking rusted bolts and screws that have ruined what should have been a painless job. I had not disconnected any of the lines or pressed the pedal while the master cylinder lid was off so I hoped it wouldn't matter.
I started the truck and drove around for a while and it is a little better but not by much. What do you think, could it be my brake booster cutting out? I replaced my master cylinder and brake lines about 2 years ago and look like they're in good shape. Any help would be greatly appreciated. Sorry for such a long explaination.

 

I had an issue with my 1986 F-150 loosing pressure and couldn't figure it out. Replaced the master cylinder and never had a problem. I know you said you replaced it buy i'm wondering if it was a brand new one or reman'd. I'm starting to learn that reman'd stuff is worthless. They use inferior parts to rebuild them. If your booster was going, you would have a hard pedal.....I may be wrong. I know that my vacuum pump belt started going on my diesel and started loosing vacuum to the booster and it would make the pedal HARD!!

 

Does the behavior change with the vacuum line disconnected (and plugged) from the power
brake booster?

 

polarisman729 you were right. I changed the master cylinder and bled the lines and she seems to be solid now. I can't remember if I had bought a new or reman'd one last time. Knowing me I would bet I went with the cheaper of the two so maybe thats why it failed. ctubutis I have not tried disconnecting the vacum line, if the problem starts again I will check it out. But I guess at that point there isn't much else to replace, the booster would have to be it. Thank you again for your help.

 

I would have to say that air bleeds past the plunger in the master cylinder or something. Didn't quite understand why mine went bad. I wish I would have pulled it out before I sent the truck to the graveyard. Ohh well.

 

Good to see everything worked out. I had the same problem happen to my '85 F-150 just recently. Needed a new Master and Left/Right Rear Cylinders also. Went ahead and replaced the hoses while at it since they are 25 years old...

Now it stops like a charm!

 

Ok, I may be paranoid but I will see what you guys think. I remember a few years ago that my dash would shake like crazy when I would apply the brakes but it has not done it for a long time unless I had to brake fairly hard. Now it is doing it with just normal braking almost like the front brakes are pulsating although I am not feeling much through the pedal. It just feels like my dash is going to fall into my lap. Could it be that the new pads and rotors are catching more than the old ones and I'm not use to it or could I have messed up putting them on? I'm by no means a mechanic but I put the new stuff on just like the old came off. Is there a way to adjust the amount of pressure from the caliper? Anyone have the same problem or a possible solution?

 

Something isn't right. Did you do front brakes? What was replaced? Sounds like the classic warped rotor if it wasn't replaced.

 

Several possibilities for the sudden shaking when applying the brakes.
Could be as simple as front tires worn unevenly or out of balance. Problem never showed much before due to low stopping force from the formerly worn brakes, but now they work better so the issue is far more noticable.
Could be the front calipers are sticking, causing excessive heat buildup, which has already started warping the new rotors.
New bearings in the front, or reuse the old ones? Are they properly secured? Loose wheel bearings can cause a wide number of issues.

Did you ever manage to get all the bleeders to open? If not, you may need to consider replacing wheel cyls and/or calipers so you can fully bleed the entire system. I also highly reccomend fully flushing the entire system at least once every 2 years. This keeps fresh fluid thru the whole system, as well as helps prevent bleeders from getting too rusted in place.

 

Gonna chime in, if it's just the shake check your rotor, most parts places will turn it and on the lathe you can really tell if it was warped bad. if it's a bad warp just replace it. If you are getting any pull to one side or the other I would check the caliper for sticking. I've done that by having a partner push the brake a release, and watching it stick...

I've had both of these happen to me (not on this ford though) If I recall a new caliper was 20 bucks at NAPA a few years ago and rotors can run about the same.

 

The rotors are new but, no I am ashamed to say I didn't replace the wheel bearings. It was one of those situations where I had everything taken off but didn't have the part and no way to get to the store so I just pushed on ahead with the old. Like I said I'm by no means a mechanic or have much experiance with brakes at all. I suppose if I did I would have had everything I needed when I started. You live and learn I guess. The tires are unevenly worn due shot ball joints and a bad alignment. The brakes don't seem to be building up any heat so I think I'm safe from warping the new rotor (knock on wood). If I were to replace the wheel bearings what else should I do, grease or replace while I have the rotor off? Any weird gaskets or retaining pieces that I should replace? Rogue_Wulff how do I ensure that they are properly seated when I replace them? I just put everything back in the way I took it out to the best of my ablilities but I wouldn't know if it was right or not. I did end up getting the bleeders loose and replaced them while I was at it and bled the lines after that. ospreyguy I will check to see if the caliper is sticking and let you know. If it sticks should I just get a new caliper? Once again thank you all for the help.

 

Reusing the bearings shouldn't be a problem, if they were in good condition. I don't the factory spec for tightening the bearing retaining nut, as I tend to go by feel. Too tight, and the rotor doesn't spin easily. Too loose, and the rotor can wobble.
If the caliper is sticking, I'd replace it. I prefer to replace calipers in pairs, and last I saw, they weren't but $15-20 each w/exchange. Small price to pay, for peace of mind.
My thought is, you are just feeling the uneven wear of the tires, coupled with the slop from worn ball joints, but it wouldn't hurt to check for loose bearings or a sticking caliper, just to positive your new parts don't get ruined quickly, instead of lasting a good long time like they should.