2003 D2 with 4.6 and in-line thermostat
Digital coolant gauge with sensor over the fan cover past the thermostat

Interesting thing happed while on the trails this past weekend. My son was behind me in the D2 and after a long very steep incline that was very slow due to traffic on the trail he shut down the engine at the top. It had just climbed to 220 fahrenheit. Was only at 220 for 5 seconds or so.

We opened the hood let it cool down to 180 degrees but starting it up it ran up to 200 quickly. We did this twice.

The third time I slammed on the accelerator after starting it up and must have pushed an air pocket through because the digital gauges quickly came down after hitting 196.

Just curious if anyone has had this happen before.

 

Air pocket is possible, inadequate water pressure, or just not enough fan. On long slow hills in hi range my temps climb as well but the engine is barely above idle rpm 1100 to 1200 tops. Dropping into low and 2nd gear makes a huge difference to my engine temps as the engine is up above 1600 rpm more water flow and better fan movement.

 

Yeah this is an interesting one. Is it possible given your description? Perhaps, but that is assuming you may have a leak somewhere. It’s also possible you had a bubble in there that finally was “dislodged” and that angle just facilitated it.

Something that is always hard with these engines that I have found is there is a sweet spot for load, revs, and speed. Too much load and too low revs, it gets hot. Too high revs with minimal load, it gets hot. Add speed into each of those and it can go both ways. Of course health of the cooling system plays a part as does ambient temp as well. Add in off road and that is another variable.

Another odd thing I experienced was I thought I had a bubble in the system and parked it at a healthy angle overnight with the cap cracked and it seemed to have helped get a bubble out. Oddly, the temps started acting wonky when I turned the heat for the first time this year and even after parking it like that I still get a rushing sound every now and then when I rev the engine slightly.

I’ve given up trying to figure it out and as long as it doesn’t get hot I’ll just chock it up to one of the idiosyncrasies of this engine.

 

Yes, possible. The heater core has the fitting located at the bottom of the core, very hard to get all the air out of it unless you really zoom the engine with the thermostat closed.

 

This is the old trick on how to bleed a RRC. Stick the nose way up (like 30-40 degrees +). I've never had to nose up a V8 D2 to bleed it though...

I also don't find D2's hard to bleed in a stock system without any air leaks or flow issues. ... if you have issues, use a vacuum filler (50 bucks at Harbor freight if you have a compressor). Works every single time and it's how dealers / indy shops do it. I don't think most techs mess around trying to bleed in 2022... vacuum filling is the way to roll.