Brakes to the floor!

I'm doing a large mechanical overhaul. After replacing the control arms, ball joints, and sway bar end links I took the car for a spin. Yes my alignment is off, but what I'm concerned about is the brake pedal going to the floor. After a few miles the pedal did firm up, but still not where I know it should be. I have all new rotors and pads that I matched up to my current. The rotors look the same, the pads do look to be a bit work on the rear, fronts look good. Before I change the rubber lines and flush all my expensive ravenol brake fluid through... I wonder if I have a master cylinder issue?

To recap, I had to front wheels off to do control arms, ball joints, and sway bar end links. Test drive was questionable, allowing the brake pedal to go to the floor. After a few miles the pedal stiffened up a bit, but not to where it should be. Master cylinder issue?

Are you sure you got all the air out of the brakes and lines?

I haven't touched the brakes yet!

When was the last time the brake fluid was changed? also there is a vacuum line that goes to the brake booster check to see if its cracked or broken.

Seems obvious they just need a good bleed. If you haven't let the fluid drop below the cylinder in the master cylinder, you should be able to just do a standard bleed/flush (1/2 L per wheel). Don't forget the clutch cylinder.
In my opinion expensive brake fluid is waste, any DOT4 works fine for all but the most extreme applications.

Thanks for getting back to me. Again, I haven't touched the brakes! And I don't know when they were last serviced. I don't understand why I have this problem...I only did control arms, ball joints, and sway bar end links...

Might there have been an underlying problem that has presented itself since I have had the wheels off the car? I really don't understand why I have a braking issue after doing suspension work?

Did you retract the pistons? Pedal will move a lot until the pistons push back out. If the master bore was bad this extra pedal travel pushing the piston over the bad area might have damaged the seals.

Or maybe a line got damaged and is ballooning?

Haven't touched the brakes

booster could be bad

If you didn't retract the pads during this work and you didn't damage a line so it's ballooning and the fluid level isn't dropping indicating the fluid is leaking out you have a bad master.

If the pedal goes to the floor the fluid has to go somewhere. If it doesn't move the pistons and doesn't expand a line then it must be going past the piston in the master.

A bad booster won't cause the pedal to go to the floor.

KLXD said:

If you didn't retract the pads during this work and you didn't damage a line so it's ballooning and the fluid level isn't dropping indicating the fluid is leaking out you have a bad master.

If the pedal goes to the floor the fluid has to go somewhere. If it doesn't move the pistons and doesn't expand a line then it must be going past the piston in the master.

A bad booster won't cause the pedal to go to the floor.

Click to expand...

it can in our cars, and it's actually pretty common... i thought the same as you until my pedal started going to the floor .. i replaced the master, same issue... decided to check my brake pressure in vcds and i was surprised to see it increasing as the pedal sank not stable or decreasing... installed a used booster, problem cured ... FYI: pedal would sink all the way to the floor bottoming out old and new master, countless bleeding (with vcds) six quarts of fluid until i figured out the true cause ... apparently the valve inside the booster dumps too much vacuum from the atmospheric side of the diaphragm causing "sinking pedal syndrome" ... the vacuum can apply a tremendous amount force to the master, more than you or i can apply without the assistance, and i tried... without the car running i depleted vacuum and watched brake pressures in vcds (not all abs modules monitor this) while i stood on the pedal and pulled on the wheel to the point where i thought i'd damage the column or wheel and could not reach the pressure while vacuum assisted ... all this extra assistance from vacuum expands flexible brake lines, distorts other components and gives the illusion of lost hydraulic pressure

What I mean to say it that there's a mechanical connection between the pedal and the master as demonstrated with the engine off and vacuum eliminated by multiple actuations of the brake. The pedal won't hit the floor. The diaphragm is there to assist the actuation.

In the scenario you describe, overboosting, the brakes would lock up unless the ABS unit is "absorbing" the fluid. Even then the system should be fail safe and there should be enough travel left to keep the brakes on.

When the OP said "to the floor" I took that to mean no braking.

So the question to the OP is did he have braking with the pedal "on the floor" or not.

Thanks for the input guys. I'm doing a bunch of replacements now, could be a bit before I hook up the vcds and see how the vacuum is.

Finished the brakes (rotors and pads all around) and all good! I did start the car while in the air and put it in 1st and did some braking before I took it for a spin. I never felt the pedal go to the floor, and the 10 Mile drive was all good. The front pads I replaced had little wear, the rears however were a bit more worn than I could see through the wheel. Still usable, but worn. The death wobble while braking at speed is now gone, and again no pedal issues. I may have an underlying issue, but nothing bad to report at the moment. However I am considering upgrading to stainless lines as I feel the pedal is soft... But Blauparts had the rubber lines for ten a piece, thus I do have them on standby. And the (most likely original) Florida rubber lines do show a little cracking....

I do have some rubbing on the passenger side, more so when turning right, nothing very bad, could be because my front wheels are a bit out of alignment (cocked out after the ball joint, control arm, sway bar link install), but it wasn't there with the old brakes... I'll have the car up in the air soon enough to look around. And will have an alignment done after I dial in the JOM bluelines...

carsaremytoys said:

Haven't touched the brakes

Click to expand...

Perhaps you did something to the brakes, did you touch the brakes, the brakes did you touch them?