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Swapping Master Cylinders - Is It Possible/Necessary?

702 Views 7 Replies 3 Participants Last post by  Zeitgeist
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!


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When I upgraded to 334mm/300mm SL600 brakes, I opted to install a 500E MC. I've heard that this may not be necessary, though there has been some discussion about stepping up to either the Limo or 500E vacuum booster as well.
Using the 500E MC just required that I slightly tweak the brake lines, as the brake ports were a little different. Other than that, it's a straight bolt-on proposition.
1 - 2 of 8 Posts
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