the salt in the water would have melted
because the car thinks it overheating so it shuts down to prevent damage to the motor
No, a physical property DOES NOT change the identity of a substance. That would be a chemical property which DOES change the identity.
There may be a hole in the radiator?
Radiator cap
If the radiator was not fitted in properly or the pipes were not attached correctly, the radiator would leak.
A household radiator is cast iron. An automotive radiator would be aluminum or copper.
A pysical property is like this: You take a stapler and bang it on the counter. It would be a broken stapler but it is still a stapler. It is still metal. Or even if you sawed it in half. It is still metal but it is metal in two pieces. A chemical property is like this: You take a block of wood and burn it. It is now ash. You have changed the material. Chemical changes are rarely reversable. You have taken wood and changed it into ash.
I would suspect a clog in the radiator.
The radiator would be specific to the truck, not to the engine.
The parts that are needed to fix a car radiator depends on what is wrong with the radiator. It would be best to have the radiator fixed by a professional.
If it could be directly observed then it would not be called dark matter!
Should be at the bottom or rear of radiator or remove lower radiator hose