Brake Pedal Fade

thompsontechs

Hello guys, I had a rather strange presentation and wanted to list it here for anyone who may run into the same deal.

I recently bought an 09 TS and the front rotor/s was warped. Sans, hit the brakes at higher speeds and shaking the wheel. What I didn't notice at the time, because of the shake was that the pedal had more travel in it than it should.

I replaced all rotors with Ebc AND Redstuff also adding Z1 hard lines. In the process I let the MC go dry.... I know I know. :P Anyway, I have a motive and bled them several times and still got excessive travel.

When you hit the brakes hard all four would grab fine, but if you eased up on the pressure (returning to normal brake application for even stopping) the pedal would begin to travel down, but only 1-2 inches (not to the floor) and then firm up and the car would pull like a truck to the left. If you increased pressure without pumping you would get an ABS activation on the left front. Hmmm

Since I ran it dry I wasn't sure what was next, by letting it go dry I had increased the possible problems... (Air in ABS or MC) A sanity check revealed the next step. I took it out and hit the brakes quickly and very firm and all four corners are working... then some more pedal travel and the left front issue.

This was the key... By hitting the brakes hard and fast the pucks inside the MC expanded and sealed properly momentary and then you would get some blow-by and the pedal would start to travel again. This has a different feel from air in the lines or a booster issue. The key is if you get a good application hitting it quick and then more travel with steady pressure then you need to look at the MC (Master Cylinder)

I replaced the MC this morning (don't forget to bench bleed folks) and installed it. Bled the brakes and took her for a cruise. Pedal is perfect, brakes are a bit grabby, but that is to be expected until they bed.

Conclusion: I think the MC was weak and that this cause a heavy application to the left front and right rear for some time. The wear on the right front would suggest this is so. Now, the final fail was letting the MC go dry, at which point all that crud and crap that sits at the bottom of the reservoir (I don't think this one had ever been flushed or replaced) makes it's way down into the seals and finished off the MC. It was much worse after that than before. I would have noticed it even with the warped rotor/s.

I know this car, in particular has issues with the res going dry, but I think there is also a design issue that makes it worse when that crude gets sucked in as it goes dry. I think this could be part of the problem when people never really get their brakes back to the way they were. It's possible those seals ingest that garbage and are never quite the same after.

By the way, hello forum!

JT