Brake pedal goes to the floor...

For the brake experts out there...

My 2002 explorer which doesn't get much use these days..

The brake pedal pretty much goes to the floor. I can still stop.. but I don't feel like I can "lock em up". It doesn't feel safe if I had to slam on the brakes.

With the car off, I can pump and hold the pedal. but as soon as I turn the car on, the pedal goes to the floor.

I was thinking air in the lines.. but with the car off it doesn't feel spongy at all.

Now I'm wondering if its the master cylinder? There is no evidence of leak and I
don't seem to have low fluid level?

Is it worth trying to bleed the lines at the calipers?

Is the master cylinder hard to change? (I feel comfortable enough to change the caliper if I had to as an indication of my skill level)

The truck as about 130K on it... and the fluid has never been changed as far as I know.

Thanks,

Jim

chances are, what u have is air in the line but better to be sure,,have your boss, the one who knows where all your and her stuff is at, pump the pedal sevral times under power,,and hold it on last pump,, take cover off and look in ,master cylinder, not directly but off side in case return fluid is violent,tell her to release the pedal, watch how much and how fast it returns, if its a lot or foamy u have air,, its better to have some one knowledgable help u bleed the first time and watch how its done, if your master cyl was bypassing there would be fluid between the master and the booster, loosen the master cyl bolts to booster body, lift it away slightly,, if fluid drains from the maiting face, reolace the master cyl
,, hold pedal down so its sorta hard, hold it,, if the pedal eases down, its bypassing, that s failed, replace it

i just bled the rear and I'm about to do the front. I only got the tiniest bit of air. I did a test drive and it's better but it still isn't right.

What it feels like is that I can't slam on the brake because there is resistance to
get to the point where the pedal stops. I was incorrect.. it doesn't really go to the floor.. but it's take a lot of force to get the pedal to the point where it stops.

I did notice that one of my rear calipers tool much more force to return the cylinder back in than the other one when I replaced my rear brakes yesterday.

Could a stubborn caliper explain my symptoms?

I got a set of rears and I'm tempted to just replace the "bad" one.

I'm going to bleed the front now and see if that does anything.
This is a good exercise anyway to flush fresh fluid through the system.
The "bad" caliper did have dirtier fluid than the "good" one.

Jim

everything about those disc brakes have to mobe freely, if u had dirty fluid in there, u prob also had water, is the boot solid, no holes??that will suck water,, take calipers from mount, sand , clean slide points si it moves in and out freely, as the piston engages, caliper must move an equal amount so both pads press equal amount,, if one pad wears, the caliper is sticking,u can bleed from top down or u can pressure bleed from caliper up,, from top down, do rt rear then left rear then rt front then left front,, if u have a lot of black sludge in the bottom of your master, clean it out or reolace, when bleeding, make sure to keep plenty of fluid in master or it will suck aitr and u will have it tod do all over again, u want clean clear fluid in there, buck

bleeding abs

http://www.brakeandfrontend.com/bleeding-abs-systems/