Brake problems

[peterson3829]

'93 Ranger XLT 2.3L I have replaced Power Booster, Master Cylinder (twice), RABS Modual, Rear Center Rubber Line /w distribution block, and both wheel cylinders. As well as the front bleeder screws. Lifted front end and turned the wheels, applied brakes wheels stop. Front calipers are working. While bleeding from furthest point to closest you can hear rear brakes working. At all four corners while bleeding into a bottle of fluid there is pressure and no bubbles.
Bench bleed the MC twice, no bubbles except micro bubbles in front line. Went thru about 3Q of fluid so far. Hears the issue, While truck is off, good pressure at the peddle, turn truck on, peddle goes to floor. While driving, peddle goes to floor, truck slows but does not stop like it should. I have read on this forum lots of ideas, tried all that sounded reasonable, no luck. Please help, been on this for two weeks, need my truck buck on the road. What am I missing?

 

[peterson3829]

if anyone can help, please e-mail me at peterson30851@gmail.com thank you in advance.

 

[martin]

Did you adjust up the rear brakes?

 

[peterson3829]

Did you adjust up the rear brakes?

Yes I did.

 

[adsm08]

A bad booster could do it, as well as a small leak, something where a line isn't tight enough. I've had those hold with the engine off but leak when the booster is doing it's thing.

 

[peterson3829]

A bad booster could do it, as well as a small leak, something where a line isn't tight enough. I've had those hold with the engine off but leak when the booster is doing it's thing.

I have searched down the entire line, no fluid leakes anywhere visible, the booster is a new one and according to the Hays manual procedure for checking booster, booster is ok. Still scratching my head. I have never went through so much fluid just to bleed a brake system.

 

[Mark_88]

+1

With all the parts you've recently replaced there is bound to be at least one small leak...I found a couple on mine by loosely wrapping blue shop cloth around the joint and looking for the wet spot after pumping...hmmm...never mind...just my mind working overtime...

That would also depend on why you started this overhaul in the first place...if for the same reason (pedal to the floor) then it may be the booster...but I've also had new brake cylinders leak after a new install also...maybe pull the drums and check for fluid inside...

Do you hear a loud or prolonged whoooooooosh when you push the pedal down?

 

[Andy D]

Living in the rust belt and driving old heaps/ classics, I've replaced beaucoup brake lines. I have found that a gravity bleed will prove a system's integrity. If you can't get a gravity bleed, there is a leak. Snug up every coupling you have worked on. I replaced every hard line and most of the hoses on the Rat. In order to get a bleed, I had to re-tighten every single coupling from the MC back to the rear wheel cylinders. Mark's advice about using dry paper towels to check for leaks is a good one I use it too.

 

[enjr44]

I used up a whole sheet of paper explaining why I think this; but, it went away, so cut to the bottom line.

I think the master has an internal leak.

 

[Andy D]

Then it would have had 2 bad MCs. Possible but unlikely

 

[alwaysFlOoReD]

Have you checked the integrity of the firewall? Flexing of the wall can cause problems. I've personally seen a master with one bolt ear broken allowing the master to move. And I've seen a crack in the firewall also allowing movement of the master. Both instances act like air in the lines.
I've also heard of flexlines ballooning.

 

[peterson3829]

While bleeding the system one more time, I noticed the front caliper on the passenger side was not moving at all while my dad was pumping the pedel. On the driver side the lower part of the caliper was moving but not the top. Question. If the piston within the caliper is moving but the caliper itself is not, will that give you the feeling of no pressure in the pedel? Last test run seemed as if the rear was doing the stopping not the front, truck did stop, but not untile pedel hit the floor.

 

[Mark_88]

Am I missing something here?

The piston in the caliper is all that actually should move...it pushes the pads against the rotor to stop the vehicle...what else is moving?

There are sliders on these calipers if I recall correctly...been a while since I pulled my fronts apart...but they just move in over time...as the pads wear...and they might be sticking causing the whole caliper to move, but the caliper is bolted down and is not, typically, meant to move...

maybe I need to go out for a break brake refresher course, but if you grease the sliders and install the pads over the rotors then the sliders will move inward and outward fairly freely...and you should not loose pedal pressure when that happens, unless the pads are not installed.

 

[peterson3829]

No bolts on calipers, mounted only with "slider" pins.
My brakes are fixed noe, turns out that the steering knuckle that the calipers are mounted to got slightly bent while removing the old ball joint two weeks ago. Did some grinding where the calipers sit and pow, I got brakes again. Guess I didn't notice the knuckle getting bent when using the hydralic press. Lesson learned.
Thanks to all that posted.

 

[Mark_88]

Good to hear you've got it working...the slider pins were the type I was familiar with but have since upgraded the frame to the bolted calipers...figured that happened around 1993 so it wouldn't be an issue...

Another new day, another new lesson!