Pretty simple question but I could not find it answered anywhere.

I'm wondering what our coolant system comprises of. I was interested in putting in a coolant heater but was wondering how much you can actually circulate the coolant while the truck is off.

There isn't any pumps or anything that will stop coolant from flowing until the engines running is there?

What about the thermostats? They would slow it down but there is a bypass pipe that allows some flow until the coolant reaches 180F when the 'stat starts to open, per the Helms manual. (The front 'stat is the one that controls whether the coolant goes to the engine or the bypass.) When the coolant gets to 185F, the bypass starts to close and more coolant flows through the block. The front stat should be fully open at 203F, and the rear stat will be fully open at 212F. Even when fully open, the stats cause a deliberate restriction to prevent cavitation at the water pump. Helms is great at explaining things!

But wouldn't you be better off by simply plugging in your block heater?