Nicholi2007

CAR: 2009 C350
MILEAGE: 141K
ISSUES: Brake pedal soft. I don't think the previous mechanic bled the brake system properly after replacing brake fluid. so it could be that but....

Q. Has anyone replaced the master brake cylinder and at what mileage? I presume around 125K is when it should be done.

Opinions please.

ItalianJoe1

Should not have to replace at a normal interval. Have the system bled properly first. Why was he working on it?

Nicholi2007

The brake fluid was brown and needed to be replaced.

W204Motorsports

Master cylinder will last the life of the car. No way should they need replacing at 125K unless you ran the system dry or never replaced the fluid. Pumping out the fluid from the reservoir and refilling with new fluid every 2 years goes a long way. Bleeding it out and flushing it is what you should do every 2-3 years.

Moto_Guzzi

Hi, I am sure I read somewhere theres a trick if not done right you get the soft padle.

I had my fluid replaced and brake pads/rotors under guarantee, and afterwards sure I felt padle softer than before on normal breaking, howevr if I apply speed limit where it slow down with that and then step on the brake as well, it feels hard and normal, well thats how I still drive it years later, it is now time for a fluid change again, I actually forgot about this.

ItalianJoe1

We flushed fluid using a pressure system on the reservoir to avoid getting air in the system, but it sounds like it just needs to be bled correctly if it was normal before and is now feeling spongy or soft. Replacing fluid will make no difference to the feel of the brakes.

Nicholi2007

It should be noted that I exceeded the 2 years at one point. It might have been 3 years.

ItalianJoe1

Doesn't matter, I've had plenty of cars where the fluid was never changed and the master cyl lasts decades. It's not a normal wear item.