[BILL WILLIAMSON]

Originally Posted by Willynch

Thanks for all the insight.

Maybe I misunderstand the purpose of the overflow tube. I thought that allowed overflow to spill out. If the radiator was overfilled, this overflow tube would take of that problem.

I have been filling the radiator close to the top. It sounds like that might be a mistake. If so, why is that a mistake? Also, how do I determine the proper fill level for my radiator and my car?

Also, I do not understand why placing a roofing nail (suggestion by Bill Williamson) would be useful? I picture that as a way to obstruct the overflow tube which I assumed was there for a purpose.

Lastly, I also hope my new radiator is not just an "expensive filter". I have barely 50 miles on the car since the radiator was put in. I have drained and refilled it three times; each time the fluid has looked very clear. Hopefully that means I am OK. Lot to learn

Willy, The nail is a proven old time "fix", it just sits there, doing a little "dance" , acting as a "splash over" shield & it WON'T pressurize the system. At higher REVS, the water REALLY churns in the top tank & water is gradually lost out the overflow tube, by "SPLASH" over.
AND, remember, for those that have a MOTO-METER or a temp gauge, on long runs, you notice the gauges CYCLE UP & DOWN, at about 1 1/2 to 2 MINUTE intervals,---You are LOW on WATER!
AND, like Mitch//pa said, be concerned about Rust FLAKES that get stuck in the upper ends of the radiator tubes!!! ANY amount of cleaning of blocks & heads, NEVER totally eliminates the rust flake problem. A BI-ANNUAL BACKFLUSH, helps.
IF, you could count the number of tubes, you'd be SURPRISED, at how FEW there are! IF you are able to ever see a chunk in a tube, you can suck it out with a MAGONET
AND, DON'T worry about OVERFILLING, that's what the overflow's there for, to belch out excess coolant, when it warms up & EXPANDS. But if you're running Anti-Freeze, it's important NOT to overfill & belch out/dilute your EXPENSIVE stuff!
NOT tryin' to be smart assed or loooong drawn out, jist tryin' to share what I've SEEN/DONE!
Bill W.