You guys worry to much about engine temps, as long as you are under 215 you are fine, spike around 220 still fine.
And yes turning the heater on does drop the engine temp that much, even more if you are parked facing the wind.
Idling a diesel in the winter with the heater on will cool the engine off to under 100*F.

 

I'll take Spike's advice as very few people have more miles with an Ultra Gauge.

 

Don't both of you have d 1's anyways?

 

Yes, much fatter radiators. And in the next day or two I will drive mine 70 mph and note the temp change when enabling the heat and report.

 

And I run a 195*F t-stat, my truck runs right in the 195-199 range all day long once warmed up.

 

Well I just have to join in. I am new to the temp game...

I have a D1 and use Torque Pro on a Android phone to monitor the engine.

Yesterday it was 45 here in North Florida - and once the engine warmed up to 186 it was steady.

I was driving on a state road with the cruise control set to 45 mph per the gps. No traffic lights. This is Florida. Flat. Boring.

HEATER OFF - 188.8 steady for miles

HEATER ON - 186.8 steady for miles.

Tried it back and forth for a 20 minute stretch - there was defined 2 degree difference with the ON.

Not saying it means anything, just an observation.

 

Temps will drop with the heater on. It was an old trick of mine when the electric fan went out on my Mazda Protege back in college when I had no money. On hot days if I was stuck in traffic and the temp gauge was rising, if I turned on th heater at full blast I could keep he engine in the safe zone. Sucked for me, but kept my engine from cooking. It is not recommended by me, but it worked long enough for me to save and get a replacement back then.

 

Turing on the heater is a old trick to stop a overheating engine from cooking itself, open the windows, turn on the defroster, turn on the heat, turn the HVAC fan to high, all the heat goes out the windows, then you remove the load from the engine and it will start to cool off.
If you have complete coolant loss than you will not have any heat and the temp gauge will continue to climb, in that case you turn the engine off.
Never turn off a overheating engine, unless you have coolant loss or lost the belt.

 

Stumbled upon this just now. Your 25,000th post! And thanks for your time and wisdom shared on the site.

 

This morning 28F - cranked D1 and ran at idle. After 45 minutes, engine 180. Turned on heat. Temp dipped a few degrees, then came back to the 180-183 range. Drove 10 miles at 60 mph. Heat on and it would drop, then return back to where it started from. Note - 180 stat installed.

So - I would agree that is engine overheating and you have coolant you might make some difference, because you are indeed adding more cooling. But - if your are running below the fully wide open temperature of the stat, adding this extra cooling simply is compensated for by the thermostat in a few cycles. And if you are above the wide open temperature (stated as 204 for a D2 in the RAVE, but is that 204 inside the stat or 204 inside the engine?) - and the extra cooling reduces the temperature AND continues to hold it lower, you'ld have to ask if the main radiator was clogged up. Because the heater core is smaller than the main rad and the air flow is less.

I can't see driving the vehilces for long periods at temps well above fully wide open on the stat. No matter which stat you have. But if you want to drive around at 221....