Ice cold. Which is the exact opposite of the weather in June in the Phoenix area. Sure, you've heard the urban legends about melted asphalt, and frying an egg on the sidewalk (neither of which is true, by the way), but even more horrifying is the actual proven fact that an AMC Eagle can overheat in such conditions. Yes, I still have the Eagle. It clings to me like a scared child, and I can't help but feel sorry for it and give it food and shelter.
Several times in the past few weeks, the following scenario has played out...
After driving from downtown Gilbert to the north end of Tempe, I pull into a parking spot at work, nervously eyeing the coolant temperature gauge on the dashboard. After I shut down the engine, I wait about 15 seconds, and I start to hear a low, gentle rumbling sound from under the hood. The coolant is boiling. Bubbles of water vapor are surging into the coolant reservoir, from the connecting hose at the top of the radiator. No steam comes out from underneath the hood, but the message is clear: you're really pushing it, dude.
In a perfect world, I would be able to drive a moderate distance on the freeway during the hottest part of the day, during the hottest part of the year, in the hottest metropolitan area in the country, with the air conditioning on full blast, in a 30-year-old car, without the engine overheating. Is that too much to ask? I for one have refused to take "yes" for an answer.
I tried modifying the fuel mixture. It helped a little, but not enough. I put in a brand new thermostat. It helped a little, but not enough. I know that radiator was made to handle some pretty serious heat, so something's not quite right. Then there are all the other classic cars (of which there are a lot in this town) that you see driving around, apparently shrugging off the heat like it ain't no thang.
So it was, as always, time to consult The Internet. Inspired by some posts on enthusiast forums, I realized that there are probably all kinds of rust and mineral deposits in the radiator from when the car sat idle for months and months. That, and just the fact of having so many gosh-danged miles on it, and being so old... you get the idea. And all of that inibits the flow of coolant and probably heat transfer as well. I read about a heavy-duty liquid rust remover you can get at Home Depot, and I ventured forth to procure some.
Last night I made a solution of said rust remover and ran it through the radiator a couple times, letting it sit for a while in both instances. I also washed the outside with it, including the millions of thin copper fins running between the coolant passages. This was with the radiator out of the car, of course.
After a very thorough rinsing with water this afternoon, the radiator is back in the car, with all the coolant, and all the hoses hooked up. Based on preliminary observations from a small road test, it looks like the radiator is dissipating heat a little better than before. Tomorrow will be the real test, though.