S420 master cylinder replace
 

I suspect some of you guys have changed the master cylinder on a 95 S420 and could give me some tips.

Specifically, do I need to get a new brake fluid reservoir at the same time as the master cylinder or can I re-use the old one?

Are there any other gotchas I should pay attention to?

Thanks for the advice...

The brake fluid reservoir should be reusable unless it's cracked or leaking. There's no pressure in the reservoir so it should last indefinitely. Are you sure you need a new master cylinder? It's possible that you merely need to pressure bleed the brake system due to trapped air.

S420 master cylinder
 

Don't think so.

I've had the S420 for 2 years. The brake pedal has always been a bit soft, at least compared to what I'm used to. (I also have a 94 E320 and the brake feel is much different.) I parked the S420 for the summer/fall 05 and when I took it out just before xmas, the pedal would sink all the way to the floor.

I'm able to 'pump up' the pressure, but if I do the press and hold, the pedal sinks down to the floor again.

I tested the vacuum using the key off, pump pedal until hard, hold pedal, start engine, pedal sinks a few inches method and that is ok.

Thanks for the response.

Bleed the system first starting with right rear, left rear, right front then left front, check for line leaks, if the pedal does not stiffen up you might have an internal leak in the master cylinder, not hard to replace about a 3.5 on an scale of 10