No, it heats the engine as the heat rises thru the coolant from the hose and into the engine. Doesn't heat up quite as fast as the block heater but fast enough to decide not to bother trying to remove the plug on my other cars that needed a heater.

If I had the manifolds off with easy access to the plug I might think otherwise. However, the amount of effort people have described using to loosen that plug has made some people think there is the possibility of cracking the block during the removal procedure.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13