Date registered: Apr 2007
Vehicle: 2006 E320 CDI
Location: Midwest USA
Mentioned: 4 Post(s)
Quoted: 143 Post(s)
When you put the distilled water in and you find its not leaking was the engine running at anytime during the 3 hours?
The coolant was already low in the radiator
The water pump is slinging the coolant/water and its evaporating.
You have a bad radiator, not sure but many have the transmission cooler built in and the distilled water in getting into the transmission, but probably not.
Check the oil for contamination of water too