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So I’ve had this issue since last week. It popped up middle of nowhere.
When I cold start my car, a whining high-pitch noise starts and it stops as the RPM drops below 1. It appears from time to time for few seconds when the engine is on.
I figured it’s coming from a part ‘servo brake’.
I’ve had few research but couldn’t find any similar symptom.
My break fluid is clean and filled good amount. I don’t know what’s wrong with it. I will go get it checked soon but I wanna know if someone has ever had same symptom on 2009 Mercedes B200.
Brake boosters are typically vacuum powered. Check the vacuum line that comes from the engine, typically from the inlet manifold (or similar) for leaks. That maybe the sound you are hearing as brake boosters usually don't make a noise unless you are depressing the brake pedal and even then, they're silent. As the noise reduces as the engine rpm subsides, it might be a simle repair with a new hose or at a minimum, tightening where the hose attaches to the booster.
Brake boosters are typically vacuum powered. Check the vacuum line that comes from the engine, typically from the inlet manifold (or similar) for leaks. That maybe the sound you are hearing as brake boosters usually don't make a noise unless you are depressing the brake pedal and even then, they're silent. As the noise reduces as the engine rpm subsides, it might be a simle repair with a new hose or at a minimum, tightening where the hose attaches to the booster.
I just figured that not only it makes noise when I start car but it does whenever I brake. Like you said, it seems there’s higher chance of air leakage from hose. I’ll take a closer look at it. Thank you so much 👍
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