I am stomped and need some help.

After a routine brake pad replacement the brake pedal hits the floor when applied with normal force. The pedal feels like a badly leaking master cylinder, but prior to the pad replacement the brake pedal was firm as a rock with no drop at all. If I pump the brakes the pedal will come up to normal height, but if I then maintain light pressure the pedal will again sink to the floor.

1. Truck was braking fine, however pad 3/4 worn
2. Replaced front calipers, rotors and pads
3. Replaced front brake feed hoses
4. Replaced rear pads
5. Started engine
6. Started bleeding from furthest point from MC a) passenger rear, b) Driver Rear, c) passenger front, d)driver front. Did it two times...

Still, brake travels all the way to the fire wall and never develops tension. Moreover, sometimes, when person pumping brake puts pressure and i open bleed, no fluid comes out. Could it be a failed master cylinder??? I tend to think it's not because 24hrs ago, the pedal felt fine and the truck was braking ok.... So much for preventive maintenance.

 

The Pedal "drop" you are feeling is a classic symptom of a weak master cylinder allowing fluid to bypass the internal seals.
All that new fluid and bleeding probably dislodged all the crud that was keeping the seal inside the bore.
I would certainly try to bleed it some more to be sure.Having replaced only the front calipers, you should only need to bleed the front. BUT if you were seeing air while bleeding the rears that is a good indicator that the master seals were weak to start with.
On the bright side, its better the master failed in the shop and not while driving.

 

Thanks Axe, I guess you are right. Better that it failed in my back yard. I have a new master coming from Amazon, should be here on Tuesday. So a simply swap, and then re-bleed? Thanks

 

Better safe than sorry


Be careful when bench bleeding and after when bleeding on the truck.
Pushing the plunger down far into the bore can damage the new master


Most of the time it wont, but we have a guy at the shop who pumps the brake like his leg is on fire and he has had a few masters fail.
Pump easy and not too fast, and when opening the bleeders don't force the pedal to the floor. You can close the bleeder before the pedal is to the floor and bleed an extra few pumps just to be on the safe side.

 

This is why I pay to have brake work done and it's guaranteed for a year. With brakes, you will know before a year is up if something is not right.

 

You will know the first time you hit the brakes man.

 

the problem started by bleeding the back end........ you replaced the hoses on the front.... now you have air EVERYWHERE........ all 4 ends will need to be bleed.

 

I wrote that I DID bleed all 4 ends....

 

pads and rotor, I'll stick to the back yard... Cuz, then they would have hit me for another 300 to replace the MC. Tell you what, it took me less that 5 seconds to know, there was a problem - not a year

 

Doing your own maintenance is a good thing. You can save plenty of money and learn at the same time.......... what I ment by bleeding all 4 corners was that I was not necessary in the beginning.. You only changed the hoses in the front. Possibly when you went to bleed the back, you introduced some of that air into the rear end......... at this point your right, all 4 corners will need to bleed until all fluid is seen, no air. I agree with the post that "slow and steady" is the pumping sequence. With pedal down, open the bleeder and let out some of the air/ fluid... don't let the pedal go to the floor or backoff until the bleeder is closed............. Your on the right track now !

 

If the pedal will get firm (by pumping) but can't maintain firmness then the MC is bad.

If it doesn't get firm with pumping it is either a bad MC or too much air in the lines.

 

Just changed the MC, brake still soft, but do get some bite. Haven't bled it yet will need for wife to get home :-). Will update later today. Fingers crossed. Thanks

 

I have one other question... Why is it that the brakes go SOFT, once car is on?

 

Gents, just bled. Turned on car, and brake still goes to floor! Stomped!

 

Do you have discs in back, or drums?