TLADILA

When I release the brake pedal I hear a hissing sound like air is leaking. Any idea why this would happen, haven’t done any crazy driving lately and the brakes function fine, no leaks where I park either. Will the problem be fixed with a break fluid flush?

GreekUPS

Brake master cylinder?
EDIT:
Brake Booster, my mistake. Let us know what the dealer says.

bzammitt

Common on the '15 C300/C400, it's the brake booster. Happens more frequently when it's colder

mau108

Ya I have this when the weather is cold. Don't have it now that its warm.

TLADILA

I’m having this problem on a 2017 C43

what about it though?

I notice this all the time, the sound fades the more I drive and use the brakes, sometimes when I hear lots of hissing I look at the brake fluid reservoir and it looks almost empty but the brakes function and if I park the car and let it sit for a bit it raises up to normal levels. Is this normal?

GreekUPS

This....Let is know what the dealer says.

TLADILA

Any ideas on how I can diagnose it myself? I hate bringing my car to the dealership, every time they treat my car like **** and end up damaging something. Last time I was there they even turned off my camera that I had filmed inside the car. I worked at a dealership before and we used to **** around a lot I bet it’s the same thing at Mercedes, people taking cars for joyrides/lunch break. I hate the dealership so much the only way I’m going there is if my engine grenades.

GreekUPS

I’m not a mechanic so I have no clue. I had the hissing in my C300, brought to dealer where they replaced the brake booster and fluid. Not taking chances with brakes. Check online for videos to see if you’re hearing the same sound and go from there. Be safe.

TLADILA

thanks man, I’m just going to flush the break fluid and see if that fixes the problem, if not I may have to goto the dealership or a mechanic. I’ll post my results.