Brakes wont work after draining fluid????

[Positive Vibes]

How can I tell if my bladder/booster is good or bad???

I was thinking, I replaced the hydraulic control unit a couple years ago.

 

[410Fortune]

well typically if they hold vaccuum (wiggle the line going to the booster, if air rushes in, its holding vaccuum) they are still good. But they do wear out internally.

Other then that I dont know, I would imagne they can be tested with a vacuum pump and some sort of measurement of the hydraulic pressure in the brake lines??

 

[Bored_2wd]

Hi Guys,
If I can jump in here, I'm confused and probably wrong in my thinking. I'm not sure you want the rear to lock up just before the front. From how I understand it, when a tire locks up it has less sliding resistance than just before it locked up. More resistance on front wheels and less resistance/no sideways control in the rear means a spinout. The factory sets up vehicles to lock up front first just for this reason. This can be illustrated on ice where when you lock up the front wheels you don't typically spin out, but instead continue straight ahead. The thought here is when you start to slide you haven't lost all control and releasing the brake allows you the ability to steer again.
With the rear locking up first, you don't slide straight, you spinout. You release the brake but now momentum is pushing you sideways so it keeps going.
What am I screwing up in the thought process?
--Bob

 

[Rick]

I agree... As I said earlier in the thread the bias is about 60/40 with the fronts getting more than the rears.

 

[Glacier991]

The question no one wanted to answer was the issue of the "is there something special to "'prime' the ABS pump?". On 94 4 wheel ABS models, here is what the FORD manual says:

NOTE:

The anti-lock brake system must be bled in two steps.

1. The brake master cylinder and Hydraulic Control Unit must be bled using Anti-lock Brake Adapter T90P-50-ALA and Jumper T93T-50-ALA. If this procedure is not followed, air will be trapped in the HCU which eventually leads to a spongy brake pedal.

To bleed the brake master cylinder and HCU, disconnect the 40-pin plug from the Electronic Control Unit and install the anti-lock brake adapter to the wire harness 40-pin plug.

a. Place the bleed/harness in bleed position.

b. Turn the ignition switch (11572) ON. At this point the red OFF indicator should turn on.

c. Push the motor button on the adapter down. This starts the pump motor. The red OFF indicator turns off and the green ON indicator turns on. The pump motor will run for 60 seconds once the motor button is pushed (you do not need to hold the button down). If the pump motor is to be turned off for any reason before this 60 seconds has elapsed, push the abort button and the pump motor will turn off.

d. After the first 20 seconds have passed, push and hold the valve button for 20 seconds. This bleeds any trapped air from the brake master cylinder and HCU.

e. The pump continues to run for an additional 20 seconds after the valve button is released.

2. Bleed the brake lines in the following order.

l Right rear

l Left front

l Left rear

l Right front

In another (now much older) thread I showed pictures of the 90-ALA, and for quite some time have advertised a couple of relatively inexpensive Thexton knock off units on the For Sale Forum. I once chimed in with this info but learned to keep my mouth shut. Would failure to follow this lead to "pedal to the floor" ? I dunno. Just my 2 cents.

 

[410Fortune]

Wow what a PITA that is.

 

[Positive Vibes]

Thanks Glacier!!!!!

 

[Positive Vibes]

Ok. I need to get this fixed before the winter run and truckhaven. I called the stealership and of course they don't have the tools Glacier mentioned. They did say the could fix it for $80. As much as I hate the dealership I think I will go this way. Just curious to what they say when they find out the ABS is disconnected.

 

[Positive Vibes]

Took her in to the stealership for a $70 brake inspection. Turns out its my master cylinder. Anybody have a master cylinder for sale from a '95?

They looked at my ebrake but wouldn't touch due to the brake conversion. I still need to figure out how to tighten the ebrake cable???

 

[Positive Vibes]

Picked up a new master cylinder for $140.

Any tips or what not to do's when installing???

 

[Positive Vibes]

Ok, got the a new master cylinder. Blench bled that puppy according to 410 and installed it. Bled the brakes and the break pressure got a little better. Bled them again until new fluid was coming out. The breaks still go to the floor. I can stop but wouldn't want to have to stop fast. Took it to the stealership. Of course they have no idea and don't want to mess with it due to the ABS not working and the disc brake conversion in the rear. So what could it be guys? They say the booster is good, the MC is good, the abs module was replaced 2 years ago. Any ideas? Really want to make Truckhaven this year but I'm not bringing her down with the spongy brakes.

 

[410Fortune]

wow the dealership coundt figure it out or they wont touch it?

new or old calipers?

Bleed more or powerbleed what about the special ABS module bleeding proceedure/tool?

 

[Glacier991]

I'm suspecting you need to use the tool and purge your abs system. I've got one you can borrow.

 

[Rick]

Did you adjust your master cylinder pushrod length after the rear disc swap???

 

[Positive Vibes]

Did you adjust your master cylinder pushrod length after the rear disc swap???

Ummm, no?? Not sure on how to do that??? Do you have a procedure on that?

410, They couldn't figure it out and are scared to dig any deeper. New calipers (2-3years).

410 and Glacier, they tried priming the abs pump. They tried everything they could think of. They are pointing to the proportioning valve but, I ran her for a couple of years with no problems. Thing that gets me was the only thing that changed was a brake line and the fluid got really low.

 

[410Fortune]

Like Rick said you might need to check the adjustment/setting of your master cylinder pushrod, Haynes book shows exactly how to set it back to the factory depth.

If you didnt touch it then its not likely your problem.

Brakes worked fine before the conversion to rear discs?
It is possible yuo got a bad master cyl, who did you buy it from?

 

[Positive Vibes]

Like Rick said you might need to check the adjustment/setting of your master cylinder pushrod, Haynes book shows exactly how to set it back to the factory depth.

If you didnt touch it then its not likely your problem.

Brakes worked fine before the conversion to rear discs?
It is possible yuo got a bad master cyl, who did you buy it from?

To my knowledge I didn't touch the pushrod, unless thats the part I had to cycle in and out of to bench bleed it.

Yep, brakes were fine for two years or more.

The MC was brand new got it from Turlock Auto Parts part #E150612.

The stealership said as far as the could tell the MC was good. Thats the first thing they were pointing to cause I intalled. But they say everything checks out and they don't have a clue to how to fix the brakes.

 

[Glacier991]

When you say they "primed" the ABS pump, how did they do that ? The FORD book procedure calls for use of 90P-50-ALA which actually runs the pump. (There are aftermarket ones that do it as well) and they plug into the PCM harness.

It looks like this on the "business end"

and side view

 

[Rick]

If you didnt touch it then its not likely your problem.

No... if you didn't touch it it most likely IS your problem. You have to lengthen the pushrod over the stock length when you do a rear disc swap. I did mine and without lenghtening the pushrod the pedal went to the floor. You need to take off the master cylinder, and lengthen the pushrod a little at a time. A little goes a long way...You don't want to go to far or the brakes will drag.

This is from Brett Groom's article:

After the brakes have been bled, remove the 9/16 nuts that mount the master cylinder to the power brake booster. (Do NOT loosen any brake lines). This will expose the pushrod for the master cylinder. In order to maintain a good pedal feel after the conversion, the rod must be adjusted to push further into the master cylinder. With the closed end of a 9mm box wrench, hold the pushrod, and with a 7mm box wrench adjust the nut on the end of the pushrod. This procedure is trial and error and will require you to test drive the vehicle in order to get a desired pedal feel.

 

[410Fortune]

Okay sorry for the confusion, one of these days I will learn to read old stuff before posting answers.

I wonder if we could get the specs on the length from the factory based on the 91-94 and the 95+, see if there is a difference.

Nevermind....hahaha I will measure off my stock 96 if you measure on your truck PV before you adjust it...
(length of the pushrod from the edge of the booster)
this will tell us how far out you SHOULD turn it, instead of all by feel.