Bad Brake Master Cylinder?

[CanadianDirty30]

Hey guys,

I need some help asap to diagnose my problem this weekend. Today i was driving and my brake pedal has started going down to the floor when i brake. It still brakes slightly at the very bottom. I have read this is most likely a result of a bad master brake cylider. would this be correct? I do no have any leaks in brake lines, and there is no air in the system i dont think. Any info would help!

[agent]

Moved to the appropriate section. The FAQ/DIY section is for staff-approved instructional posts only.

[whodwho]

A failing MC will typically start leaking or will the pedal will start sinking to the floor when light braking and still work ok when firmly braking and progressively get worse.

If it is going straight to the floor it is probably air or not getting fluid. I recently pulled my MC and the grommet for the reservoir was breaking down and there were chucks of rubber that could easily blocked a port.

[CanadianDirty30]

Well at first it was fine when braking hard and then when coming to a stop it would go down further slowly. It goes all the way to the floor now because it's gotten worse. But I'll check out all the grommets and see if any things breaking down. Not sure how air would have gotten in the system I haven't done anything with the brakes like flushing the fluid or anything like that ever.

[jeffnhiscars]

When you are stopped at a light if the pedal sinks slowly to the floor it's your master cylinder.

[CanadianDirty30]

When you are stopped at a light if the pedal sinks slowly to the floor it's your master cylinder.

Yea that's what happens, started sinking when stopped. Now ithe MC is gone completely I think so it just always goes to the floor now

[stonea]

Get a 25mm master cylinder when you replace it

[e30_world]

Your master cylinder could just need new grommet seals underneath reservoir. Just did this to one of my e30's and problem was solved. Another way is to hook up the brake reservoir and do a pressure test. That's how I found my leaks.

[CanadianDirty30]

I found a master cylinder and brake booster for not to expensive, so I picked those up and the problem should be solved once I install