panic stop=pedal to the floor

[Smash9002]

I had to stop really fast yesterday on the freeway, my car is an 89 325i, so it has abs. When I stomped the pedal it went to the floor, and I had to go into the shoulder so I wouldn't hit the car in front of me. It was bad. My brakes were bled last year by a shop when they replaced a leaky proportioning valve, so does this mean my master cylinder is shot?

[AlarmedBread]

Did they bleed the abs pump? if it was full of air and cycled it can cause some issues.

[Smash9002]

It was done by a Bmw shop, they have been in business for as long as I remember. I can only assume that they bled the brakes correctly. From what the Bentley says, it sounds like I most likely need a new MC. I heard autozone sells rebuild kits, anyone know how much $? Or would I be better off ordering a new one from BMA?

[netcsk]

Could be master cylinder or a broken brake line.
Do you see any brake fluid leaking under the car?

[BigD]

Could be master cylinder or a broken brake line.
Do you see any brake fluid leaking under the car?

+1 that's my guess too, probably ruptured a softline.

[DrMcDave]

if you need a MC I have a used one.

[DCColegrove]

That's not good...

Have everything checked.

[Smash9002]

Ok, got in the car today and pumped the brakes a few times with the engine running (in the driveway) and I couldnt get the pedal to go the floor again, Im thinking I will start with installing my braided stainless lines, then bleed it. I dont think the pedal ever went to the floor during my panic stop, because I can't get it anywhere close now. The original lines + heat + new (less than a month) rotors and pads front and rear are more likely to be responsible. Either way its pretty scary when your brakes dont work the way you want them to when you really need it! Is there a way to test an MC to make sure its functioning correctly?

[BigD]

Sounds like your MC is toast, or at least half of the circuit (assuming you saw no leaks during your tests).

[Smash9002]

I have a new theory.. vacuum leaks.

[Tbolt]

when the pedal went to the floor on my 96 jetta 2.0 it was the MC, probably the case here too

[Danny]

I got an MC and I'm semi local.

PM me.

[clavinZERO]

vacuum leaks would make your pedal hard as hell, not go to the floor. The vacuum gives you the power assist in the push of the pedal, so loosing vacuum does not sound right. I agree with Colgrove... check everything over. If the MC is as old as the car, just replace it anyhow.

[Hallen]

In PRO3 racing, most of the guys disable or remove the ABS for just this reason. There are times when it goes goofy and doesn't allow pressure to the calipers. It is usually only apparent on the track I think so it might have to do with heat. I don't mean to scare everybody who is using the ABS, it doesn't happen often. But that is one of the possibilities.

[AndrewBird]

Are you sure it wasn't just brake fade from shitty pads?

If the master cylinder is bad, it wouldn't work anymore at all. When they go, they go. Could be badly deteriorated soft lines that expanded under the sudden extreme pressure.

ABS sounds like it could be it though as well. Are in the system would definitely give you no pressure until it was all pumped out. Does the pedal feel spongy now?