Just installed the JCW Brake kit from Outmotoring with new rotors on the rear for good measure and switched the brake fluid to Super Blue at the same time.

I have bled the brakes using the two man method 2 times now and I'm getting clean clear blue fluid out of all 4 brakes and I have no leaks but the brake pedal is so spongy that I don't get full braking until 1/2" from pedal bottoming out.

Haynes Manual says it's either trapped air or a bad master cylinder. Has anyone else experienced a problem when switching brake fluid?

 

Sorry to bring up this old thread, but I may have the answer for you. When I had my JCW brakes installed I noticed they felt spongy too. Basically it's because you are moving more pistons with the same size master cylinder. so basically it takes more volume of fluid to move the brake parts. This is what I was told by the tech. The stopping power is there, but it does take a little more travel to get them to engage. I found that they take a thousand miles or so to really seat. After that they felt much better to me. Maybe I just got used to them.

 

You might want to try engaging the ABS and then rebleeding using the two man method.....I initially used a pressure bleeder and after cycling ABS a few times/two man bleeding it was back to normal (pre JCW install feel).

 

When you say engage ABS, do you mean slam on the brakes in wet conditions? Or is there some way to do it electronically?

 

I have a similar issue and was told the stock rubber lines are flexing after 45,000 miles and 5 years. It was recommended to replace the lines to stainless braided lines. Anyone here have experience with that?

 

I do have ss lines. For me, i think the effect is secondary as it helps more with modulation feedback in situations such as trail braking.

I noticed the many OEM shops have a pump they use that cycles the ABS and does a great job with trapped air.

 

The BMW shop computer will cycle the ABS, I don't have that so just getting the ABS to activate at speeds less than 30MPH should work as well.