Some people taking part in this thread (which is about people parroting things they have heard without the knowledge to back it up, not just Acetone/ATF mix) could become aggressive or abusive. Keep it nice, guys. Good to see it hasn't gone that way too much yet but.....
There is another oft repeated line out there about overheating. Many say that if the water circulates too quickly, it doesn't spend long enough in the radiator to cool down so the motor gets hot. Well, if it circulates that quickly, it won't be spending enough time in the engine to get hot either. Then there are those who say when water is discharged from the top tank that the pump is moving more than the core can handle so it must be plugged up. Think about that. The only place the pump can get water is from the bottom of the radiator. That water must have already gone through the core from the top tank, thus leaving exactly the same amount of space there for what ever the pump delivers. It is a closed system and only circulates what is in it. Water overflowing the top tank is therefore not caused by the pump being too strong. Grinding impeller vanes is would not be addressing the issue.
Some cars used to have a wire coil (like a spring) in the bottom radiator hose to stop it collapsing when the thermostat was still closed and the pump was trying to move more water than it could get. A restricted radiator would cause the same thing and that was a dead give away for a restricted radiator. The Model A has a solid bottom hose so don't have that diagnostic tool. Now, to get a conversation going, I'd like to outline a test I think would prove whether a radiator is restricted on a Model A. From experience, I know there will be some who already disagree with what I have said but I hold the above to be true.
I haven't had the need to use this test but it all makes sense to me. I'd like to hear (respectfully) what others think of this:
Remove the thermostat if you have one and refill the cooling system. Attach a tube to the drain cock in the bottom hose and submerge the other end in a container of water on the floor under the car. Start the engine and run it at medium revs. Open the drain cock. If the core is blocked, the pump will be trying to move more water than the core can provide so it will suck water from the container on the floor. If the level drops quickly, you have a restricted radiator. The quicker it drops, the worse the restriction. A slow drop might be observed even if the radiator is new so that wouldn't cause for a lot of concern. If the level in the container on the floor rises, your radiator is super good. Give yourself a smiley stamp.
