Cossie,

If you remove the radiator cap immediately after shutting down a hot engine, it is normal to see smoke. It is basically oil vapor and not necessarily a negative indication.

Blow by is basically a condition where an excessive amount of cylinder pressure which is produced from combustion "blows by" the rings into the crankcase. Whenever the blow by becomes really excessive, it will be blowing oil out the valve cover vent into the intake, drawn into the cylinders and burned. It also can cause problems with the crankcase ventilation system causing leaks and other problems. This is typically associated with a high mileage or improperly maintained engine.

Hope this helps,

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Larry Bible
'84 Euro 240D, 516K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles