Swapping Master Cylinders - Is It Possible/Necessary?

Hi all,

I recently have been experiencing brake firmness problems and I need to ask a few questions regarding this.

When I brake, sometimes the brake feels perfect, like new, and it has only been 10 months since I replaced the pads, rotors, sensors etc. But sometimes three stops later, I feel the pedal loosen up, sometimes to the point where I worry it is not gonna stop. Then randomly it will firm up, all in the same trip. I can't tell when it is gonna cooperate.

So after reading a few posts it seems as though the master cylinder might be the culprit or the vacuum hose. All in all, if it is the cylinder, I was wondering if anyone had put in a stronger m/c? If it needs changing I might as well go "all out" :thumbsup:

I am also looking to get bigger brakes for my 400E and was looking at the 500E 320mm and possibly the 334mm setup. But if I do go bigger, do I really need to put in a bigger m/c? Will the one for mine suffice? I would like to know so when the time comes, I can do it right the first time! hehe

I was looking online and it seems that some of the 400E's have the same or close to the same m/c as the 500E and 500SL. I have a chart that shows all the m/c part numbers and which cars they were applied to, but I am still a little confused.

So if I do go with the 320mm or even the 334mm "big brakes" will I need to get different lines/booster/pins/etc. or is it just direct bolt on?

I have found almost no posts on this subject so any feedback will be greatly appreciated. Thanks!