C270CDI - How completely should the turbo vacuum valve seal?

JoeHorner

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Your Mercedes
2003 W203 C270CDI Elegance
Slowly working through potential issues for our intermittent loss of turbo and today was vacuum time.

The system has a healthy (I guess) 25 inHg vacuum at idle, with 18inHg appearing at the turbo connection when the valve is energised.

But, even when the electrical plug is physically disconnected, there's a very slight hiss of air being sucked through the valve and you can feel suction with a finger over the connector. With a gauge it's only showing between 1 and 2 mmHg but my gut feeling is that "shut should mean shut"?

Can't see such a low leakage causing issues directly but could indicate wear in the valve which might cause other issues?
 

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