So, my D2 is a trail rig and this option likely isn't practical for everyone, but I thought I'd share...

I have a factory cooling setup at the moment, minus a throttle body heater, with the gray 180 stat.

The experiment: well, I ripped out the dash and factory heater/ac a while ago, and threw in a universal heater core in a custom dash. It works, but I decided I don't really need the heater, so instead of doing a bypass loop on the heater core, I simply capped off the heater hard pipes. This dropped my hot idle temps from 195 ish to 182. It makes sense... the heater circuit bypasses the radiator, sending hot coolant out of the engine, through the heater core, and back into the water pump. If you have the heater on it works like a mini radiator, but if the heater is off, you are not taking off much heat, if any, before it goes right back into the engine.

I think the same thing applies to the port on the intake that sends hot coolant to the throttle body, then to the tank, then right back into the engine, bypassing the radiator. I plan to delete that line as well, leaving a short hose stub out of the intake with a valve on it for easy air bleeding.

The cooling system is working harder than necessary to offset the uncooled coolant from the heater and throttle body circuits.

My next plan after all that- and this is likely overkill and unnecessary - but I plan to switch to an inline thermostat, a custom radiator w/ tank.cap, and dual 12" brushless fan (Spal or Delta PAG), deleting the expansion tank and mechanical fan altogether. Super simple plumbing... water pump -> inline stat -> radiator -> water pump. No radiator bleed line, no TB heater line, no heater line, no expansion tank! Now, if the thermostat is closed, there will be zero flow in this design, so I will need to experiment with adequately sized bypass holes in the thermostat to ensure constant circulation. The electric fans will be thermostatically & PWM controlled, so I don't see an issue in letting a fair amount of coolant flow through the radiator when cold.

 

[QUOTE=Jeff Blake;862957][...the uncooled coolant from the heater and throttle body circuits./QUOTE]

Wrong, the heater and the throttle body do help to cool, dissipate, absorb the coolant heat. You reaaaaally want to cool the coolant to the maximum ? ----> Remove the thermostat and bypass hose and feed the water pump inlet directly from the radiator outlet. It may risk running too cold in winter.

 

[QUOTE=Externet;862978]Sure, if you have a TB heater or heater core... I don't.

 

Some good thoughts there Jeff. I run a dual electric setup with a fan controller on my trail rig (kit coming) and it absolutely is able to control temps in a tighter range even without a thermostat installed via airflow control, at least at speeds below highway speeds. Regarding the flow through the radiator i.e. constant circulation, to keep a smooth temperature profile you only need a small hole in the thermostat to bleed enough coolant past the thermostat so that it can sense the temperature without too much lag. The hole in the thermostat I provide in the inline kit is just about perfect for that.. I have experimented with larger but they tend to let so much coolant past that it delays warmup in very cold temps (due mostly to heater bypass flow as you stated).