Originally Posted by Charlie Foxtrot

I use this style of heater on back up gensets & equipment that I maintain. I have not put one on a Benz, but there is no reason not to. The trick is to install it between hoses so that the heated coolant circulates through the block. The bigger units have a pump, the smaller units act like a percolator moving the heated coolant up into the block. I don't use the lower radiator hose as a source, rather, I tap into the block. There is no reason not to use the lower rad hose, though it may be slightly less efficient. In any event, the return line (heated coolant from the top of the Kat's htr) should be routed into the block via the heater return line, ie: tee into the heater return line close to the block. I use insulated (red) heater hose for my runs to & from the heater (less thermal loss). These a good, relatively trouble free coolant heaters. I recently pulled a working heater off of an old 1945 jeep engine generator - it was over 40 years old & still working. BTW - which model Kat's are you installing? I have been thinking about adding one to a cold blooded '85 300SD.

Good luck!