Too much coolant can cause overheating

Reading the story about the guy with the FPV FG Falcon with the thermo fan that keeps coming on after Ford replaced the water pump and filled with a new type of coolant, and thought it sounded like it may be an issue I have come across a couple of times. Most modern coolants are ethylene glycol based with the common mix being 50 percent ethylene glycol and inhibitors and the rest demineralized water. This can come in the form of a premix or a 100 percent ethylene glycol concentration with the dealer or end user mixing it to the 50/50 glycol/water mix. The premixed versions are now the most common but there are still plenty of the 100 percent concentrates around. Concentrations of up to 60 percent ethylene glycol are permissible in countries where temperatures get 20 degrees plus below zero or more. However, while ethylene glycol has many advantages, it does not transf er heat as well as clean water. Excessive concentrations will cause a significant elevation of engine operating temperature - easily noticeable on the gauge. In the case mentioned, if it was a 100 percent glycol mix and was not diluted correctly it would account for higher water temperatures and more frequent cycling of the thermo fan.