Now if removing the vacuum from the booster allows things to work ok.

Like in the olden days when I was a youth. without power brakes.

By logic it says the problem has to be in the area of the booster / Master cylinder/ Brake pedal.

Is this not true!!

If the rod is not adjusted correct if there is no clearance the brakes will drag

To much clearance and you will have long pedal travel before anything happens.

Now with disc brakes as the heat builds up they get tighter and tighter .

Now if this rod has no clearance it is also possible it is pushing the piston in the master cylinder to far allowing fluid to be where it should not be.:jessica:

Swapping a Booster I bet not many check the rod adjustment.

If you are 100% positive the booster and Master cylinder are good the adjust the linkage rod it is sure cheaper the new calipers.

Good Luck.

 

did you ever find a fix?

 

Nope...... I just plugged off my vacuum an been using manual brakes. I changed hoses on front and it didn't change anything. All I have left to do now is adjust that linkage on the booster. I just been really busy with work I haven't had much time. It's been dark lately when I get home and I don't have a garage. So I temporarily fixed my problem until I can really tear into it.

 

by any chance are your calipers and rotors from a 2wd they are thinner than the 4x4 models just keep that in mind

 

Just thought I'd update this thread. I now have my brakes fixed. I hadn't posted because I just bypassed my vacuum to the booster and been running without power brakes. But anyhow my problem was caused with by the linkage in between the brake pedal and brake booster. If that thing is not set perfect you will either have terrible brakes or your brakes will stick really bad. I found out from my experience that a brake booster will put pressure on that linkage once it gets vacuum. There for if your linkage is adjusted to tight it will put force onto the brakes. If its adjusted to little then you will not have much brakes at all. In my case it was adjusted to tight. But anyways it's fixed and if anyone out there has any questions feel free to ask.

 

Good to hear you got if fixed.The push rod adjustment was the only thing that made since to me that migh cause the problem.

 

Yeah that's all that was left as well lol

 

Having the same problem. Is the linkage you talk about in the cab, under the dash, or internal to the booster/master cylinder? Thank you for your help.

 

Okay, found the adjustment mentioned above. Seemed to work but guess not. Still can only drive for short distances before the fronts start to lock up. Pulling the vacuum hose off the booster definitely relieves vacuum but still have to wait for something to cool down (usually 5-10 minutes) then the pedal feels normal and I can drive a few more miles. So far I've replaced the calipers and rear wheel cylinders. Any help would be greatly appreciated. Thank you.

 

There's an adjustable pushrod between the master and booster, it normally doesn't need to be adjusted unless replacing one or the other. There's another adjustment between the brake pedal and booster, up under the dash where the pedal linkage is. Either one could cause that, or a defective master that was assembled wrong.

 

I've been adjusting that rod all day with little to no changes. Also, if I remove the vacuum line and plug it, shouldn't that rule out the booster or rod? I'm confused. It seems only time and cooling is working so far.

 

Is the pedal getting rock hard when this happens?

 

Absolutely.

 

Get it to that condition, then completely disconnect the linkage rod from the pedal, pull back (toward driver's seat) on it, reconnect it and see if it's still hard. If it is, replace your master cylinder.

 

Thank you. Tried that. Couldn't really seem to pull rod rearward but tried, reconnected and still rock hard.

 

So what would be wrong with the master cylinder? I took it off but it seems to at least move in and out freely on the bench.. What's it not doing? Just so I understand.

 

I once had a rebuilt master that had a cup seal installed backwards, it acted like a line lock.
Check the pushrod adjustment between the master and booster, there should be 0 clearance. Too much clearance or too little and it won't work right. See page BR–17...
http://personal.utulsa.edu/~nathan-b.../5brakeboo.pdf

 

Okay, thanks. I plan on replacing it anyway. Can I adjust that rod without that special tool?

 

It can be done without the special tool, but it's tricky.

 

Great. I don't suppose the new part comes with the instructions on how to do that.