Engine running hot

The ability of the cooling system to effectively cool the engine depends on several factors. The coolant must be full, the thermostat must open when it is supposed to and the cooling system must be sealed so that is maintains pressure. A failure in any of these areas will cause overheating. The only way to know for sure what is causing an overheating problem is to have the system analyzed by someone who has the training and tools to properly identify the problem. To answer the second part of your question, no, a coolant flush will not solve this problem. Dirty coolant will cause problems, not because dirty coolant doesn't cool, but rather, because dirty coolant can cause corrosion which will cause leaks and/or plug up small passageways that will restrict coolant flow. Changing the coolant before it causes damage is a great idea but if the damage has already been done, flushing is kind of like closing the barn door after the horse has escaped. Good luck