Poor brakes at low speed and sucking noise from the pedal to booster connection
 

Odd thing on the 97' Ranger that showed up today. I was backing out of the spot at the local Shell station, (on an incline) and the pedal went to the floor. Never happened before. I pumped the brakes a few times, and they came back. On down the street, slowing for the stop sign, pedal went to the floor again.
Not throwing codes, fluid levels are good, only seems to happen at lower speeds/idle. Sometimes pumping brings the brakes back, sometimes they come back all of a sudden.
I can hear a "sucking" kind of noise coming from where the pedal connects to the booster, up under the dash. I looked at it, and nothing *appears* to be broken.
It almost feels like the pads are against the discs, and the pistons/calipers have to reach for them before the brakes apply. (If that makes any sense)

There should be about 50% of life left on the pads, but i haven't pulled the fronts wheels yet to look.

Anyone got any ideas?

And thanks in advance for your help!

You may have more than one problem.

The sucking sound around the brake pedal makes me want to suspect that the vacuum booster diaphragm is ruptured & your hearing intake vacuum at the leak. Disconnect & plug the under hood vacuum hose connection at its booster connection point, drivers side firewall area & see if the sucking sound stops.

With the pedal going to the floor, you may have a worn brake master cylinder bore, or damaged rubber piston seal that's leaking fluid under pressure around the piston.

Let us know what you find.

Dont have anything to add, but both of paws ideas are what I was thinking.

Thanks! I will check that out. I'm still confused as to why the brakes "come back", and why I am only able to reproduce the issue at low RPM.

Thanks again, I'll let you know what i find.

Just a thought, but I think there's less vacuum at lower rpm's - higher rpm's = more vacuum and a higher likelihood of the brakes "coming back" if the leak is relatively small. But, by that theory, the "sucking" noise you described would be more noticeable at higher rpm's so, I dunno...

I had the same problem before (without the sucking noise) in a b2000, where the pedal would go straight to the floor and I would have to pump it to get the brakes back. I have to agree with paw paw about the piston seal. As you push the brake (if the seal is worn out), it may have a tendency to bend and give, allowing fluid to leak through and you lose all your pressure. That could be the sucking sound you are hearing, although you wouldn't hear it from the pedal? It would explain why you would have to pump it because as you do, the seal will re-seat itself and you would get your pressure back.

I ended up getting a remanufactured master cylinder (with a lifetime warranty of course!) and my problem went away.

It is possible that the sucking noise is the powerbooster itself. I had a 91 honda that had brakes but they were terrible because my powerbooster was broken. I too experience a sucking/hissing noise until I replaced it.


Good luck, hope you get it working!
Craig

I popped the hood today to check the vacuum hose that connects from the manifold to the booster, the hose is fine, but the tension clip thing had slipped. I got that slid back into place, but no change on the brakes.

I did notice there is fluid all down the front/bottom of the booster, right below where the MC bolts to it. I'm starting to suspect it's multiple things.

I'll have to check autozone for a MC rebuild kit, but I suspect I'm going to have to get a whole new MC.
Do Explorers of similar year use the same booster and mc? (I'm going to buy the rear end of an explorer for the 54...if the booster and mc will fit the ranger....2 birds, 1 stone.

Your master cylinder is worn out and it is blowing by the piston when you press the brakes. I personally would buy a new one, unless you just want the experience of rebuilding the master cylinder. Knowing you you will enjoy the rebuild they are easy.

FYI just looking at autozone the PN for your ranger is the same for the same year model explorer. However it looks like 98+ they started using different master cylinders and there is a different part number for if you have cruise control or not.

Did you remove the brake booster vacuum hose & look to see if it was wet inside with brake fluid???? If it is & you've been loosing brake fluid from the brake master cylinder reservoir, the brake booster diaphragm is ruptured & engine vacuum is pulling brake fluid into the intake manifold to be burned by the engine. Not a good thing to have happen, so the engine oil & filter should be changed. This vacuum leak will corrupt idle strategy & the fuel trim & tables, so while doing the repair, a battery B- cable disconnect, to wipe the KAM's old fuel trim tables, will also wipe the corrupt cold & warm idle strategy. So, after the repair, doing a cold & warm idle strategy relearn procedure may prevent possible driveability problems after the battery disconnect/KAM wipe.

I agree with replacing the brake master cyl, new or reman with a warranty is suggested. Home rebuild quality is questionable, as you may have master cyl piston bore problems not visible to the eye & who wants to chance not being able to stop!!!!

Let us know what you find & how it goes.

Fixed!

For all of you that said "master cylinder", my hat is off to you. You were right. Papaw, mfp, Furyus1, Birdman, SloppyJoe...thanks for the input.

A few closing notes:
Nobody sells a kit for rebuilding your own. (Not O'reilly's or AZ)
New MC @ AZ: $69
New MC @ O'reilly: $85
Reman @ AZ: $65
Reman @ O'reilly: $35

Getting the reservoir separated from the MC was a pain. For just being plastic, stuck into aluminum with a little rubber grommet...Had to put it in the vice, use a piece of wood to distribute the pressure, and pry at it, firm and steady. IF you crack that reservoir, it makes the same sound as $50 bill flying out the window.

The seals in the MC, around the piston didn't appear to be damaged, but they did look worn around the edges. I guess 13 years of use will do that.

I checked for leaks around the check valve (where hose connects to PB) by plugging the vac tube (that goes from booster to the manifold) with my thumb and pushing the break pedal. Check valve was ok, no cracks or fluid in that hose either.

And lastly, but most importantly....Lesson Learned. Brake issues are not trivial, and need to be addressed immediately. If your brakes are "going out", it means they ARE going to fail, and probably sooner than you think.

I completely lost brake pressure just running up to the corner store today. Limped her the few blocks back to the house in 1st gear, dragging the e-brake to stop. I promised God today that anything of mine with a brake problem gets parked, immediately. That could have been a disaster.

:-jammin Great to hear you got it sorted!

Good find, fix, feedback & to hear all seems well & your safely "on the road again"!!!!

Another thought for consideration is to completely flush the brake fluid system with new Motorcraft brake fluid, which is a really high quality product, at least every 3 years, to keep it fresh, so that moisture absorption doesn't cause corrosion in the system components, or the fluid to boil during a panic stop, or during a long down hill run with a load on & the pedal goes to the floor, because the old fluids boiling point is out of spec from moisture absorption!!!!