soundquest

My brake pedal travels abruptly (and I mean abruptly) about two inches toward the floor when I brake really hard. The pedal is not spongy at all, and it does not require a heavy foot to activate them (brake booster is working in other words). Also, when the pedal all of a sudden moves like that, it makes a grinding sound that is tactile and travels through the pedal it self. I think the brake master cylinder is failing internally and that pedal movement is due to fluid pushing back into the master cylinder past a bad seal. Does this sound reasonable? Has this happened to anyone else? Thanks in advance.

wyoming9

iTrader: (1)

Have you checked the rest of the brake system ??

Pads and rotors and Calipers working like they should ??

Have the rubber hoses been replaced old hoses can balloon on hard brake applications.

Rear shoes and drums adjusted up from using the emergency brake??.

If they are not Long pedal travel to shoes contact the drums.

How many miles on the Master Cylinder ?? They do wear out .

soundquest

Thanks for the help. Yes... I have checked (and replaced) brake shoes, pads, rotors, drums (because they needed it). However... the brake line ballooning theory is very probable now that I think about it in terms of what the brake pedal does and how abruptly it happens. Kind of like when you try to blow up a skinny balloon with air and it does not balloon until you reach the critical PSI... and the WHOOSH, all at once! This exactly describes the pedal issue I am having. Will check it tomorrow night when I have time and report back (two person job). Thanks for the tip mate.