Prius block heater mod
 

I've wondered a few times if it wouldn't be more beneficial to modify the coolant thermos to accept a block heater. You could heat up the coolant in the thermos to a much higher temp since it is insulated. When you key on, that coolant would dump into the engine and be much closer to operational temperature. Of course, this would require some fabrication work. But, if you could find an old thermos for a descent price, you could modify to your heart's content without having to worry about messing yours up. This would really help with the warm up cycle.

Sounds like a really good idea. Obviously you're planning ahead. :)

You want a switch and a thermos and the stock system.

If you go with thermos only your coolant temps will skyrocket and likely boil out. If you as you already know use the tank it dissipates.

Switch is for a valve to open and close. close while the heater is on to run coolant into thermos not tank and then close when the engine comes on to reroute to tank to avoid overheating.

You could put it to a switch so if it gets really cold in the winter you can cycle in and out to maintain optimum temps.

Yeah, I'm gettin anxious. I'd really like to buy one, its just very much up in the air right now.

Good point about the temp/pressure issue theunchosen. I'd have to make sure it has a thermal switch to disable the heater should it exceed ~210F. I'd like to keep the heat in the thermos instead of releasing it into the aluminum block that will quickly dissipate heat. I've noticed that the Matrix won't warm up above ~90F in the cold of winter even in the garage. I credit this much to the aluminum block.

Yeah aluminum would do it lol.

Might want to have the shut off valve for the thermos a good bit below 210. A spike could send you to fan on mode and destroy your FE whereas alternating back and forth between the thermos will keep it safe and not as fuel efficient but you avoid the costly fan issues.