The radiator in your car is part of the coolant system that allows your vehicle to maintain a proper temperature for your engine. The radiator itself allows the coolant to cool down by pushing air past it and dissipating the heat. Fluid takes longer to heat and is easier to get rid of heat than air. Therefore, if your vehicle has no coolant in it, and the coolant system is filled with air, it will heat up quickly and then overheat. The reason a mix of coolant and water is needed is to keep the freezing point of the mixture very low (so it does not freeze when it is below 32 degrees f outside) and to keep the boiling point high. If your vehicle starts to overheat, it is smart enough to shut itself off before any major damage is done. Unless it is in the middle of overheating, your coolant level will not affect acceleration. The fact that you have poor acceleration and your vehicle is stalling would lead me to think you possibly have a fuel or air delivery problem. I would suggest that you bring the vehicle in to your technician for proper diagnosis.
〉 Answered on Jan 9th, 2008 by Suzanne Grego, Technician at City of Philadelphia Fleet Management