Re: Engine over temp at idle
Along the lines of what MarkSF is suggesting, there are a few conditions where you will get virtually no water flow at low speed but some at higher speed. This can be caused by an air lock. Additionally, your water pump can put out no flow at low rpm if the impeller is very leaky. Raising the rpm will build pressure enough to get flow.
Did you have water coming out the exhaust when it overheated?