Wildstag
what size plugs do you use and what kind of threads do the plugs have.
Thanks Jim

 

This was not the case on my truck Vacuum Pump took a dump at 60 mph, brake went clean to the floor. Not hard at all. Had to use the EMG brake and run down the center median until I got it stopped.

Pull and replaced the Vacuum Pump as it had seize up, bearings fried.

 

I gotta say, that's the first one I've heard of. Sure it wasn't something else too?

 

i know the p-brake is working properly, cause when we put the back bale of hay on the trailer we put tit on the opposite direction to push all the bales up tight. so i set the p-brake and put the transmission in neutral. if i stayed stuck on, then i'm doing pretty good cuase i pulled that load at 60mph. I'll check the master cylinder, with the plug trick. I think this is the problem becuase if i step on it really fast and hard instead of slowly increasing prssure, it almost acts like normal for just a fraction of a second.

 

The brakes when it went were. . . let me say they were firm then spongy then softened and went to the floor.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>
Of course I was in adrenaline mode and could have Fred Flintstone’d it.
I was towing and trying to pull in a turn lane on the HWY. When I hit them I think that they were firm at first but softened up and relaxed completely. Totally different feel than when the vac assist is working. I eased it home and used the emg all the way as the brakes would feel the same way. Perhaps it was partially working so that’s why I asked about the vac psi.<o></o>
I lost a pair of shorts in that one. <o></o>
Its something you just don’t forget.<o></o>

 

When my pump went weak, or weak enough to matter, the brake light came on and the pedal felt soft and inconsistent. That is why I thought the master cylinder was bad, I thought I was leaking past the internal cylinder. I ended up replacing the master cylinder, booster and RABS vavle on the frame for the rear abs, only on 96-97's I believe, but would still get the brake light to come on. But what was happening is the vacuum pump couldn't keep up the vacuum needs of the booster so the low vacuum was triggering the brake light. I am still getting a falling brake pedal, by keeping pressure on it for a minute or so, but a lot of people claim this is normal for these trucks.

 

The original poster of this thread still needs to check and adjust the rear brakes before proceeding with trying to diagnose the hydraulic system. I haven't heard where he pulled the drums yet.

The brakes need to be adjusted to where the park brake only goes down a couple inches and the same for the service brake. It's a lot easier shown than described. I'd bleed the brakes and change out the fluid too after adjusting them. It's amazing how many times that will cure a suspected master cylinder.

 

I am planning on doing this Thursday afternoon, i just haven't had the time to do any farther investigating, so i was trying to get all the possibilities and procedures for diagnosing so that i could do it all at once rather than one thing, report, wait for response, next thing, report, wait for response, ... , and three days later find the problem.

so "pump the brakes", lol, i'm getting around to it.

 

I was just worried you were skipping ahead in the diagnosis.

Do NOT pump the brakes on your truck either. Or on any other vehicle with ABS. Personally, I don't pump the brakes on anything unless it is really old and has 4 wheel drum brakes.

These days, just push the pedal down and hold it one time while someone else opens the bleeder. After it's closed let up for a few seconds then push it down again.

If you pump it you will be chasing air bubbles in the ABS system all day long.

 

i do know that much, i was just making a joke, and apparently a bad one.

 

How hard are the "kits" for the master cylinder to put in? There are alot cheaper than the whole unit.

When bleeding, is it necessary to unplug the antilock wire?
My other gas trucks if I didn't the antilock light would come on.

 

I liked it Especially after you said it was one.

 

It's not funny when you have to explain it though.

 

alright everyone, the brake problem is on the front, and its real bad. Any one got a good write up on how to replace the front rotors? Or even one to take the hubs off to get to the rotor?

 

The new hub and rotor from Motorcraft come as one piece with wheel studs. A real nice piece. What is real bad?