Miscellaneous ramblings alert...
I'd say with cooling and a Bronco, it's all of the above. Lots of things to do, to make these old bricks-on-wheels work like a newer vehicle.
You might try this if you're ever feeling like you haven't taken something off your Bronco lately and are going through withdrawls. Pull the hood all the way off and drive it like that for a couple of weeks. During your normal commute watch the gauge and see if it made a difference.
If your issue completely goes away with the hood off, then you at least can be certain that it is mainly an air-flow issue and deal with it accordingly. Like with your ideas of fans or extra venting or sealing around the radiator. Or again, all of the above.
If you still have CNS (climbing needle syndrome) even with the hood off, then even if you do have less-than-perfect airflow, you've still got issues in other areas. Like a larger capacity radiator or water pump. Not enough fan cfm. Or air in the system. Or a partially blocked water passage. Or incorrect tuning or whatever.
If it mostly goes away, but occasionally shows up when idling, and then goes away quickly with just the flick of the throttle to get the rpm's up, then I suppose you could narrow it down to just slightly low fan cfm, or waterpump cfm.
Just thinking out loud here of course, but that all sounds at least plausible as a test to narrow down the possibilities.
Luckily your "rainy season" is relatively short and you can plan your test period around it. I imagine it could get pretty interesting driving without a hood in a downpour.
Though like was said too, it's not panic time just yet. Modern vehicles run from 195 to 210 as their normal temp with no problems. What sets the modern ones apart from the old however, is the consistency with which they can hold those temps.
It seems to make no difference whether tooling down the freeway or idling down the 405 between the 101 and 105.
Oh, wait a minute. That IS a freeway! Sorry.
It's probably "all of the above" that helps the new cars. More air flowing more smoothly through the radiator AND out of the engine compartment. Pumps and fans and radiators sized properly for the power produced. And more efficiently turning fuel into heat and removing it from the engine through better coolant flow.
Anyway, just few thoughts on the subject. I've seen several Broncos remove their hoods on the trail before to avoid overheating. It worked exceptionally well in those cases, so it could work as a test.
Paul
