Tractor Repair: Ford 8N runs for about 15 minutes, ford 8n tractor, air pockets

Question
I have a Ford 8N tractor that runs fine for about 15 minutes, then stalls and won't restart for about half an hour.  Does this sound like a bad coil or should I be checking something else?  Thanks!

Answer
I have a Ford 8N tractor that runs fine for about 15 minutes, then stalls and won't restart for about half an hour.  Does this sound like a bad coil or should I be checking something else?  Thanks!

Hi Dave.
Sound more like over heating? The engine cools and is ready to go again. Have you checked for water level and is the pump working. Also when did you last test the thermostat is it opening when required? Why not flush the system whilst you are at it.
Re fill with water –slowly avoiding any air pockets, When re starting and the engine is cold leave the pressure cap of and listen for gurgling and bubbling –and watch for a water level change as engine worms up. Seal rad cap when it has stabilised.

Does this happen every time? Assume that there is plenty of fuel.
The other thing to check is that there is a free flow of fuel and not a partially blocked or kinked pipe in the system!
Martin