i have a question sorry if its dumb. I have flushed my radiator, replaced my thermostat replaced my mechanical fan flushed the whole cooling system it it gets above 210 and risses when messing around going slow. I recently replace my mechanical fan with an elec fan and it does the exact same thing when i drive down the road cruising it sits at 210 on the dot

my question is today i turned my heater on and the temp guage dropped to just under 210 does the mean something is wrong that i am missing or is the the way it works im irritated
thanks

 

No, that's not correct.

The fact that the temperature drops when the heat is turned on means the coolant is circulating. So your pump is good.

Is the upper radiator hose hard, or soft, when the engine is at operating temperature? If it's hard, the thermostat is opening correctly. If it's soft, then it's not and that's your problem.

What did the old coolant look like? Rusty-brown? There is a possibility that your radiator is clogged up.

 

Perfectly normal.....the heater (core) is just a second/smaller radiator with hot water/coolant flowing thru it just like the radiator out front. A small electric fan pulls heat from the heater (cooling the water/coolant) and blows it inside the cab just like the radiator fan pulls heat from the radiator and blows it under the vehicle. Kinda like double cooling, when the heater is on.