Quote Originally Posted by 36 sedan View Post
The small recovery tank (tube type along side my radiator) did not have enough capacity to maintain a proper level in the radiator. On hot days (100° +) the radiator would purge more than the tank could hold, then on cool down after the radiator recovered what was in the tank, it would pull air in.

The additional catch can adds ample space for full recovery and no more air problems.
You can solve that problem by some judicious attention to your recovery tank level. Go out for a drive and get the engine up to temp, then as you pull in to your garage top off your recovery tank to the point that it is about to over flow. As it cools any air in the radiator will shrink, pulling coolant in to replace that volume when it cools completely. Repeat that cycle several times, and eventually you will purge all of the air from your radiator and it will be 100% fluid. At that point you should not see any loss of coolant from the recovery tank.

Quote Originally Posted by MelloYello View Post
If I may??? How important is the catch can??? Most of the older cars didn't have them such as my '62 so should I see about adding one?
Yes, Em, you should add a new radiator cap that allows fluid to back flow into the radiator as it cools, and a recovery tank to get your system purged of air for maximum cooling efficiency. In the old days there was a pocket of air on top of the radiator, and that's what caused most of the corrosion in the cooling system. With the new recovery tank in place, fill your radiator to the brim with your 50/50 mix of anti-freeze and water, then add the same mix of coolant to the recovery tank, about 1/2 way between the "Cold" and "Hot" marks. Go for a drive, and once the system cools completely (might take a week in Texas this time of year ) I expect you'll see the level in the bottle down a bit. Top it off to the "Cold" level, and keep an eye on it for a while to be sure it doesn't go too low. You don't want it to go dry or you'll suck air back into the system.