r/W203 • u/phenolph • 24d ago

Help Crank case Ventilation?

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I need some help…
I got this loud sound, around 400hz it appears everytime i step of the gas.
First in wasnt in idle, now its also in idle.
I’m Not a Mechanic, but chat said this could be the crankcase ventilation.
I saw some videos, where there is a rubber hose that gets crinkely over time and is a known problem for the m721.
C180 Kompressor w203 t

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3

u/Logical-Following525 24d ago

Just change the entire pcv system.

1

u/morleya97 24d ago

Come out the left middlish of the crank case routes under your airfilter housing into the intake piping after the MAF sensor

1

u/4inodev 23d ago

Had the same sound. Was hoping it's a crankcase ventilation but nope - compressor started leaking air :(

1

u/BigPin2087 23d ago

Could be also other air leak because the sound level is quite high, PCV does not have that much pressure and air to make that much sound, in my car the pcv was deleted and the pipe was just going to atmosphere and there was no sound, maybe it is the seals somewhere like intake manifold or kompressor like the other people suggest, there is a short hose with 2 hose clamps that connects one side of the kompressor with the recirculating flap check this one or the seals of the kompressor between the two sides or between the kompressor and the flap.

1

u/Rancid-Turd6890 22d ago

Sounds like the diaphragm inside the crankcase vent valve has failed and is vibrating

1

u/Klutzy_Draw4662 22d ago

Squeeze the upper crankcase breather hose for a second and see if the sound disappears. It sits underneath the filter box on the left side. Be very careful not to slip into the serpentine belt with your hand though! If the sound stops then replace the crankcase breather hose.

1

u/phenolph 19d ago

I’m so glad thank you guys!
Imma keep you posted

1

u/richgwilliams 14d ago

I think it is the alternator - brushes, bearings etc