I've replaced all lines, wheel cylinders, calipers, master cylinder, booster. bled my brakes with the truck running... and I still have no pedal... 90% of the time the pedal doesn't even come back up.. does the senor on the front of the master cylinder have anything to do with regulating pressure to the front brakes... or is it just the cruise control disengaging switch

 

Welcome to the forum

What year Ranger?
Does it have 4 wheel ABS or just ABS?

Picture here of 4WABS unit in Ranger engine bay, can't miss it, can see master in the background: https://www.ranger-forums.com/attach...10226-1819.jpg

No sensors can prevent braking, in any year

Just in general
Brakes are very simple
Brake lines, calipers, slaves have no pressure internally
Brake fluid needs to fill all of these with no air present

Master needs to be full of fluid
When you press down on the brake pedal it pushes the Masters piston forward which pushes fluid out
Now there is EQUAL pressure in all the brake lines, calipers, and slaves, so calipers and slaves expand pressing brake mining against rotor or drums

Brake fluid is used because it can NOT be COMPRESSED easily, so 10lb pressure at Master = 10lb pressure at calipers and slaves

Air can easily be compressed(blow up a balloon), so if there is air ANYWHERE in the system then that air absorbs ALL that 10lb of pressure so 0 pressure goes to caliper and slaves

 

just ABS...

 

Then not an ABS issue, front brakes should still hold pressure

Take Power booster off the table first:
Start engine, leave foot off brake pedal
count to 5
Shut engine off
press brake pedal down 3 times, should be easy to press down all 3 times then get harder to press on 4th and 5th time
If so then power booster is OK, it holding vacuum
If it gets hard to press right away then Booster is leaking
If pedal never gets hard to press then Booster is broken internally

When you replace a Master Cylinder there is an adjustable shaft between Master and Booster, its usually fine as is, but make sure, when master is bolted on to booster the brake pedal should be up all the way, if not pull off master, adjust the shaft end out farther, re-install master and check again
If Master was hard to put on, have to use wrench to tighten it flush, then pull master off and adjust the shaft in, the shaft should just be touching the master's piston when its on all the way, not pushing on the piston

Now on to the brakes
Need a friend or "power brake bleeder"
have engine off, pedal will be hard to press unless bleeder is open

Start with passenger side rear brake
Open the bleeder and there should be slow drip of brake fluid coming out, this is because the Master is higher than the slave so Gravity is causing fluid to "run downhill"
Have the friend push down brake pedal all the way, and HOLD IT DOWN
Fluid should squirt out and NO AIR should be seen coming out
Tighten bleeder screw, and then tell friend to release brake pedal
If any air came out then repeat, open bleeder again, have friend press down pedal, tighten bleeder, have friend release pedal
Repeat until NO AIR comes out

Check fluid level in Master, top up as needed

Now move to Drivers side rear brake
Repeat bleeding on this side

Check fluid level in Master

Move to passenger front brake
Repeat bleeding

Check fluid level

Move to drivers side front brake
Repeat

Basically you start brake bleeding at the brake farthest away from Master then next farthest, ect..............


Brake pedal that goes all the way to the floor(all bleeders closed) means one of three things
1. A leak in the brake system, usually easy to find, from fluid on the ground
2. Air in the brake system, feels more spongy as pedal gets to the floor
3. Bad Master, new or not, piston seals are leaking so piston is just sliding thru the fluid not pushing it out the 2 brake lines

 

thanks I just assumed that the rod in my new booster was where it needed to be I'll be sure to check that. I appreciate the help

 

Hi Ron,

I started searching the threads, and came across your reply to this thread pretty quickly. You seem to know what you are talking about, so I'd like to ask you a question about my 2003 4L 4X4 XLT brakes.

Brakes start disengaging at about 90% of pedal capacity. A short stutter, and then no brakes. Intermittent for a couple of days. Took it to the garage and they replaced: front pads, rotors, tightened rf caliper bracket bolt, replaced bolt pin and bolt lf caliper. Checked fluid level, moisture and copper content, flex lines, and brake lines.

No issues with brakes for 3 weeks. Then this issue started again. Happens when truck is hot or cold. Running for a few hours, or 1 minute. Intermittent.

It's back at the shop. they are test driving it intermittently trying to replicate. They are not so enthusiastic about this process.

Do you have any ideas? BTW, no codes coming up. ABS light not coming on.

TIA.

 

You should start your own thread

Could be the Master
Master has one piston but two sections, one for front and one for rear
Each section is sealed by an O-ring around the piston, so when you press down the brake pedal fluid flows out to both front and rear brake lines and pedal stops when both calipers and both slaves can not expand any further
If there is a leak in any of them the brake pedal will continue to go down and loss of braking
OR
If there is a leak past either O-ring in the master the pedal can go all the way down, as it can not hold pressure, fluid can escape back into reservoir

Its a hydraulic system so it applies EQUAL pressure to all 4 corners, because of this if one corner goes to 0psi pressure they all go to 0psi pressure, loss of brakes
Yes there is a proportioning valve and the 4 wheel ABS unit, but these reduce pressure and are not capable of no pressure once Master is being used, assuming no LEAKS, lol

 

Brake pedal judders at 90%, pushes back, brakes disengage. Pedal does not go to floor. At that point I am looking to not smack into something, and am just busy steering to know if the pedal does anything else.

 

Really appreciate this Ron. Am just learning and you are clear and concise. Will start my own thread.