Does the system heat the entire coolant of the engine, or just the contents of the heater core? That is, to help starting in extreme weather?

The same device has been employed by many manufacturers in the days of manual-choke carburettors - both to help starting and to heat the inside of the cabin. Russian Army and civilian-utilitarian vehicles have it as standard - on ZIL-131 trucks(6.5 litres V8 gasoline engines) it heats both the coolant and oil.

Some air-cooled vehicles and most large 18-wheeler trucks use a similar device which blows hot air instead of coolant, to heat the cabin.

Caution: if you are unsure of the device, have it checked by an experienced electrician!!! It can pose a MAJOR fire hazard if it malfunctions.

~Regards,

Nautilus

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1990 260E Sportline (that's 300E 2.6 for our American friends) -> sold
2001 E320 4Matic Elegance -> my Dad's daily drive
2005 Seat Leon FR 1.8T