04 Montana cooling issue! A little different than most, I think.

Bought this van a few weeks ago then noticed it kinda runs the temp gauge up to near the red line sometimes. Drained as much coolant as I could, flushed using some product from autozone, refilled with 50/50 mix. Bled system with bleeding screws. Problem not exactly fixed. I mean it's kinda goofy or random when/under what conditions it will start to run hot. For example:

Just earlier tonight I actually took for a nice long ride on the freeway (65-75mph the whole way). Strangely, the gauge got all the way up to a little past the 3/4 mark. Got to destination. Shut off van for about 45 minutes. Decided to take the surface streets back (no traffic to really speak of. Just regular stops at traffic lights and the like) and the whole ride home the gauge would hover around the 1/2 mark.
Now, I'm pretty sure that is the exact opposite of how it should work. If it's gonna be running hot, it shouldn't be on the freeway @ 70mph. Correct?

Not really. You have more airflow at high speeds. I would change the thermostat and radiator cap. That's cheap.

Not really. You have more airflow at high speeds. I would change the thermostat and radiator cap. That's cheap.

Yes, "more airflow at higher speeds" should mean better cooling, correct?
That is the opposite of what I described in previous post.

Yes, "more airflow at higher speeds" should mean better cooling, correct?
That is the opposite of what I described in previous post.
I misread. Is the "air dam" still on the van? I would also hose the radiator grill front and back.

When I flushed the radiator I did remove 1 little piece that was mounted like directly below the radiator (couldn't get to the drain fitting with it in place). Haven't had time to reinstall it and road test it yet. I will and post again. Thanks for the response.

Well after some research found out that apparently the cooling fans aren't supposed to come on (in low speed) until about 226°f. And not until 235°f for high speed. Which is ridiculous IMO! So now I'm looking at installing and aftermarket fan controller.

All I know is I've owned 3 of these vans.. 1998 Pontiac Transport with the 3.4L v6, 2002 Oldsmobile Silhouette with the 3.5L v6 and now a 2008 Chevy Uplander with the 3.9L v6 and when all 3 vans are warmed up the temperature gauge rests at the halfway mark and never moves and I live in Canada where it gets to -40c in the winter and upto +35c in the summer.

Now I've heard intake manifold and/or head gaskets have been known to cause this type of issue !

Things to check..
**Internet !
**Oil filler cap for cream colored sludge.
**Excessive white exhaust.
**Coolant in oil, oil in coolant.
**Wet spots on upper part of engine.
**Watch your temperature gauge on cold start to see when thermostat opens..
As temperature rises when engine is warming up you will see it drop back a little bit when it opens, as for example it is the only time I ever seen the temperature go past halfway mark on all three vans I've had. It rises slightly past the halfway mark as pressure builds to open the thermostat then drops back to the halfway mark.

Good luck