I want to rig up a fuel tank heater into the existing engine cooling system for my 50 gallon transfer tank that will be holding straight waste motor oil. The idea is to heat the oil so it will flow into the main fuel tank (via the filler vent line) quicker through a 1/2" line using just gravity. For the tank, I'm going to mount a 1/2" copper loop under the tank, heating it from the bottom. I'll run the lines down through the bed, under the cab and to the engine compartment, but where is the best place to connect the coolant feed and return on the engine?

I'll probably put shutoff valves on it so it's not heated when I don't need it to be.

 

I would connect into the heater core loop. Just figure out which comes first. After the core less heat in tank coil, before core less heat in cab. I run a hot tank on my lobster boat. It is a stainless coil that you put in a barrel and add water. Just gives you hot water to clean up with at the end of the day. It is hooked up to the heater loop.

 

Heater core loop probally toward the firewall since there is more hose to T into back there.

 

You may need to add a surge tank back there or a bleeder location to get the air out, because I think that will be the highest point in the cooling system if the aux. tank's in the bed.

 

There are also taps avaiable that go into a radiator hose and you can hook a heater hose to it. I believe the last one's I bought were in a box marked "Standard" but it's been a while. These were used in the old days on engines that were not set up for heaters, you used to see a lot of ford flathead V-*'s with these. Not sure if you can still get them or what the official name for them is.

 

That is correct.

 

Jim Lane did a write up on installing a coolant filter, here's the link to how he plumbed into the system.

https://www.dieseltruckresource.com/...d.php?t=209772

 

I heat my waste oil HE with the coolant before the tranny HE, its the hottest there and doesnt effect the cab heater.