I think you have an easy win in court, if you even need to go that far.
You know the cooling fan wasn’t working when the engine blew up.
You know that the wiring for the cooling fan was pointed out to you by the tow truck driver, and that you pointed it out to your mechanic, but he never touched it.
You know that your mechanic NEVER ensured that the cooling system was working properly after repairing the burst hose, because if he had, he would have noticed that the fan wasn’t working, and then he would have fixed and charged you for repairing the wiring.
Easy win.
BC.