Straight undiluted coolant that is meant to be mixed with 50% water would have higher viscosity and could cause over heating, but its the inoperative cooling fans that need to be corrected. There is a company that independent auto repair shops get their information from, this same information is available inexpensively for people that work on their own cars.. The information is year make and model specific, covering repair procedures, torque specifications, fluid capacities and specifications, service bulletins, component locations, wiring diagrams ect.... Alldata is very easy to navigate http://bit.ly/AllData_Repair_Manuals_Online
YOU can run stright coolant if you want. That should not make the car run hot.If the fans arent coming on you need to fine the problem.Here are some things to be checked.First make sure the fan motor even works. If so you need to check the sensor that singnals the computer.Then you have to make sure the computer is grounding the relay that sends power to the fan motor. If all is ok you need to make sure the engine is getting up to the the tempenture that require to singnal the fan sensor. IF not you could have a thermostat that is stuck open.Because the engine has to reasch a surten temperture before the fans will come on .Even when you turn the AC on.Hope this helps. Have a good day.
With The engines these days its better to have stright coolant because of all the corriosn thats in the water all it dose is make electroulss and this just eats away at your engines parts. Been doing this 37 years and never had a engine overheat bet all my egines parts last longer than yours my cars that I drive have stright coolant and 2 of them have over 400000,00 never changed a water pump on either one of them.