Join Date: Jul 2011
Thanked 359 Times in 285 Posts
I like both immersion heaters and external tank types. The immersion heater type called a frost plug heater is submersed in engine coolant against the cylinder block and warms the engine by convection heating. This means the immediate area surrounding the heating element gets hot, (actually boils) and this heat is released into the surrounding engine. A tank type heater does not actually have a pump at all but relies upon the same principal of actually boiling the coolant it's heating element is in direct contact with. When these are mounted lower than the cylinder head mounting surface of the cylinder block they will fill from gravity. Don't ever plug one of these in without giving it ample allowance of time to fill. Always leave the radiator cap off until the engine has been run a few moments after installing one of these things. If you activate one of these without coolant against the heating element they won't last but a couple of moments as they overheat. The tank type heaters have thermostats in them to regulate temperature but it measures coolant temperature, not heating element temperature so it doesn't protect itself if emptyl When they are activated, (plugged in) the element heats, the coolant touching the element boils, the entrained air of the coolant expands and explodes pushing the coolant away. You will hear them boil the coolant if listening close. The space vacated by the coolant is then replaced immediately by colder coolant and the process is repeated several times per second. Pretty simple really if you realize heat rises, and lack of heat falls. This is why most of the fluid outlets on these things are higher than the inlet. The thermostat in engines is not a 100% shutoff to coolant flow, they only offer substantial restriction to allow the coolant to absorb engine heat faster before opening.
I have dozens of each type with neither's benefits outweighing the other. I like 1200-1500 watt units myself.
The question I seek an answer for is simply; why, or why not?