That thermo valve is for fuel vapor purging. According to Steve Brotherton, this valve, which is closed below 50deg C, transmits vacuum at all throttle positions above idle to the purge valve which allows fuel vapors which have collected in the charcoal canister to be pulled with air into the intake for burning. The thermo valve is a temperature controlled on/off switch to the purge vacuum control signal. Its conceivable that an unpurged charcoal cannister could reach its dew point and leak raw fuel. Probably would be so slight that all that would be noticed would be the fuel smell (which is the purpose of the system in the first place).

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't