Nice!!

Congrats on it being something simple.

 

Yeah I'm glad it seems to be resolved. I won't feel like I'm out of the woods until I've put a hundred or so more freeway miles on her, but tomorrow we're going out to the orv park again, and that should be a pretty good test of the cooling system!

 

How much did it cost you to have this done to the radiator?

 

Okay, I'm going to loose my mind. She started running hot within about a mile of freeway driving just after leaving my house this morning. I immediately got off the freeway, she cooled, and I got back on and proceeded to drive 40 miles up some pretty steep hills without a single problem! Got to where I was going (picking up a friend to go to the orv park) and after about 20 minutes of loitering we started driving again, choosing to take a moderate two-lane back road over the giant car-eating hill of the freeway. Within about five miles of driving that hill, with very little overall grade, she overheated. Again I pulled over, waited about 10 minutes, and continued driving. The drive was hot, but within the safe zone. Eventually it dumped me back onto the freeway and I continued up the remaining half of the monster hill, about 15 miles, to the orv park. The entire freeway drive and orv park time she was perfectly cool.
Then, after a few hours of getting lost in the dirt, we were on what seemed to be a pretty easy trail when again the temp spiked. Once again I pulled over, waited a bit, and restarted. She cooled and we went on our merry way, drove home on the motorway with decent hills and the A/C blasting without a problem.

W.T.F. ???!!!!

 

Do you have a OBDII scanner that can read live data?

 

Nope, no OBD2 scanner.


Just thought I'd ask, to be completely, positively, 200% sure, which way does the coolant flow off the t/stat housing? I want to make sure I installed it facing the right direction!

Also, what are the odds that a bad radiator expansion tank cap might be the culprit? If it's not maintaining system pressure, the boiling point will go down and I'll get bubbles in the system... hence the bipolar overheating symptoms that clear themselves after a few minutes of a shut down engine.

 

Yes it could be a bad raiator cap, if the t-stat were installed backwards it would overheat all the time.
The coolant always enters the engine from the bottom and comes out the top.

If you had the OBDII scanner that read live data you could actually see what the engine temp was and determine if your temp gauge was faulty and see if it is actually overheating.

The radiator cap is cheap, throw a new one on and see what happens.
Oooo,oooo...that makes sense, since it seems to be altitude sensative, you climb a big hill, less "G"s on the coolant she overheats, closer to sea level and no overheat...

 

Driving home she ran hot twice, all I do is pull off the motorway and drive to the next freeway entrance and get back on and she's fine until it happens again.

So, looking at the t/stat cover, coolant flows toward me from the block (well, technically the intake manifold) and into the upper radiator hose?

 

Yes, the coolant comes out of the top of the engine and goes through the upper hose into the top of the radiator.
the t-stat is very easy to install backwards, I ALWAYS mark the old one with a paint pen BEFORE I take it out of the engine so that I can make sure that I do not install the new one backwards.
Typically the spring goes inside the engine, but not always.
I do not remember how it goes on a DI.

 

Okay, I'm nearly certain I installed it backwards then. Me thinking from my BMW days...

I followed the little "Coolant flow ->" marking on the t/stat itself and installed it on the assumption that it flowed into the block!