My dad's '85 Ranger 4x4 V6/4sp suddenly developed the "pedal goes to the floor" syndrome, while being driven a few days ago. (please pardon my limited mechanical experience) He has kept the pads/shoes changed regularly and the brakes have normally worked well over many years of service. After a brief test revealed little/no "squeeze" at the shoes, he suspected the master cylinder and replaced it. The problem remained, so he replaced the initial replacement, with no change.

He relates to me that the pistons/calipers "move slightly, when the pedal is pressed" all the way around the truck, they just don't squeeze with power. This is the first time that he has worked on a system that includes the "booster" concept (behind/under the master cylinder).

What tests would comprise an appropriate plan to isolate and correct the problem.

Thank you for your time!
Eric

Not sure man. Master cylinder is usually the fix for the pedal to the floor symptom. Keep us posted if you make any progress on it. I'm interested to know what it is.

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2003 Ranger FX4 level II. 3" BL, 33x12.50 GT Radial Mud Claws, Custom front and rear bumpers with winch hookups, custom flatbed, with hi-lift, and full size spare mount, 12,000 lb winch mounted under bed, Electric fan, and of course a flowmaster.

Fluid leakage? Weak hoses? Air in the lines? Bleed the master cylinder first, then both front (start at closest to m/c) and work to the back (furthest away). Check the first two items before bleeding, otherwise you're wasting time.

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'88 STX Super Cab 4x4
2.9 5spd 180,000 miles
Crappy Paint, Worn Parts,
Fix'em as they Break
when Nowhere is Now Here

fluid is going somewhere get a looking

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Thanks for your suggestions. My dad says there is no loss of fluid from the reservoir.

The mention of "bleeding the master cylinder" is the second time I have seen this covered on the site. He only knows about bleeding at the four end-points, so I will help him learn how to complete the master cylinder bleeding procedure.

Does "weak hoses" refer to hoses that do not leak, but rather balloon to locally intercept the pressurized brake fluid, instead of passing full pressure on to the calipers/pistons?

I'll report back with the MC bleeding outcome.

Thanks!

You should always bench bleed the master cylinder before installing. Just some fyi

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2003 Ranger FX4 level II. 3" BL, 33x12.50 GT Radial Mud Claws, Custom front and rear bumpers with winch hookups, custom flatbed, with hi-lift, and full size spare mount, 12,000 lb winch mounted under bed, Electric fan, and of course a flowmaster.

I will encourage him to bench bleed the master cylinder.

I really appreciate everyone's help here at the forum! My dad loves this truck! He has kept it on the road and regularly maintained, well beyond the cost and time most folks would have invested. At 80, even some mechanical things become a matter of "principle!"

I would bet there is air in the system. Especially if the master cyl was not bench bled.

And as for bleeding the system you start FARTHEST from the master cylinder and work your way to the master cyl

Good luck, keep us updated

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1993 Ford Ranger XLT, 4.0, auto, 4x4
No mods yet...

Well, the parts store encouraged dad to replace the braking system's "booster" unit and that appears to have been a complete resolution! Dad is confident now that the braking performance has returned to its normal effectiveness and reliability.

In case there is still air in the system from his omission of bench bleeding the master cylinder, I will encourage him to soon replace all of the fluid in the system.

Thanks for all of your help! We are very grateful and we wish you all the best!