Driving my 1990 300E 2.6 yesterday, slogging around town after two days of rigorous rural interstate travel, mysterious white smoke began pouring from the exhaust while sitting at a light. No miss, no bad fluid readings. No pulsing of the exhaust flow at the tail pipe. Added a can of cleaner overnight, in case it was a fouled injector or something simple.

Started it this morning. Still smoked. Drove about 1/2 mile continuous throttle on an uphill ramp looking like Schumacher after he cooked one on the back chute...and then, voila...no smoke. 188,000 miles with regular maintenance but a little long on this oil change. Ran as good as ever the rest of the day.

Similar experiences or known diagnosis?

I am not a Tech but, white smoke is usually associated with water (coolant) in the combustion chamber. Could be a bad head gasket...

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'98 E430
MBCA-Peachtree

I am a tech and have seen this on some occasions. Most of the time the coolant has been neglected in service and has eaten through the head gasket. This causes a head gasket leak and loss of some coolant.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Just a short note to add...this is not a problem that you can postpone. Running with this condition will create very expensive engin damage.