Over heating while driving

[kanji1jz]

It's been my experience that when vehicles overheat while driving at speeds on the highway that the radiator could be crystallized and causing there to be not enough flow to dissipate heat quick enough.

 

[te72]

Actually, kinda sounds like the story of my Mk2... long story short, it's easiest to start at the cheap end of the spectrum, and replace things in order of cost. Worst case scenario, as was the case with my car, you end up with an entirely new cooling system.

 

[JPsToyota]

Could be a pinhole leak somewhere (radiator cap could cause it). Or the radiator, shroud, crappy t-stat (had it happen more than once with parts store ones) could be the issue. Less likely is waterpump (they're stamped steel from the factory, the bearings go out first) and headgasket (I'd never do a headgasket unless I was sure).

The hydrofan setup should be pretty durable, so I doubt it's the issue.

To add to my earlier story, I also tried new hoses (got samco rad hoses, still using them), tried a new t-stat and no t-stat, and a new rad cap before I went crazy on everything like in my post on page 1. I'm still pretty sure it was either a headgasket leak or my original radiator was so shot that everything fully heatsoaked and then it couldn't transfer enough heat away while cruising/heavy boosting.