Brakes suddenly not working

Just after some ideas and tips :thumbsup:

Was driving normally on the way to work. Stopped at a few lights then the next time I went to brake, the pedal just sank to the floor without doing anything.

After overcoming the shock and managing to engine brake and hand brake to a near miss on a HWY, I soon discovered the brake still had a bit of bite in the last inch of play (usually the pedal would sit a good 3" above the floor, but here it was only 1" above).

This inch of movement had barely any progression and went from no braking to almost full lock. When using the brake this way, the car pulled violently to the left.

I checked brake fluid and it was at about 1/4 capacity.

I received the car back last friday after all rotors and pads were replaced and all four calipers were rebuilt. Braking worked ok under light load over the weekend, but seemed to pull to one side or wobble from side to side when braking more heavily. I thought it was probably due to totally dodgey wheel alignment, but maybe brake related in retrospect.

I haven't found any liquids/leaks in the interior under the pedals and nothing obvious around the master cylinder. Haven't jacked the car up yet, so haven't checked brake lines.

Anyone got any ideas what could be the problem?

Mastercylinder. Bleed the system first and see how that goes.

Turn off the engine and pump the pedal a few times does the pedal get harder?

fatboy, when the engine is turned off and I pump the pedal, it definitely gets harder. What does this signify?

im guessing it is your master cylinder, because i had same problem with the leaking master cylinder, brake pedal sank to the floor when at lights or something and had to keep pumping. With the wobbling part of things, it could be warped rotors? but then you had them replaced so im not quite sure. but the sinking part i would say is master cylinder

I guess wobbling or leaning to one side could be proportioning valve, a burst hose on one side, air on one side... dunno what else...

if your hose bursted, your brakes wouldn't work at all, because all the fluid is gone.
when you pump the pedal when the car is off, hold it down, and see if it goes down, if it does, your seals insiude youe master cylinder are gone.
get a rebuild kit, if that's the case.
and get it done asap, becuase the more you drive like so, the more damage you can do to the bore inside where the pistons are in the cylinder, and if it is too damaged, you can't rebuild it, and you will have to get a new master cylinder.

destrukshn: your theory explains the pedal sagging, but does not explain the unpredictable pulling to the side when braking.

Seems pretty likely it's the master cylinder, but it's probably something else as well, like proportioning valve? Or maybe there isn't even a problem and there's just air in the brake lines on one side?

How can I tell what is causing the pulling to one side? I tested it on smooth surfaces at various speeds and pressures on the brakes. It happened on all tests, except very light/progressive braking.

Not ruling out warped rotors, but it seems highly unlikely, given they are new.

Have you bled the brakes again? Do that first.

pullling to one side....hmmm trying bleeding the brakes again. Something doesn't sound right.

Could be mastercylinder but mayb there's a big air pocket in the brake system. Bleed the brakes again cause its a cheap option.

Quote:

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Originally Posted by Dylanamus

I received the car back last friday after all rotors and pads were replaced and all four calipers were rebuilt.

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Have you at least contacted the place that did the work?

could it be a large air pocket that escaped/formed?

Must have been a bloody scary experience. Good thing your ok tho :thumbsup:

bleed it again. like jimmy says its a cheaper option. Car serving to a side could be caused by air inside the brake line on the side that the car swerves to. Air causes one side to be more biased that the other. Oh and don't go back to the mechanic that did your brakes for you ever again.