Hello,
When an engine cools down while driving it is due to a stuck open thermostat.
As the thermostat stays open the coolant circulates thru the radiator becomes cool and cools the engine.
When a thermostat works properly it stays closed until the preset temperature then opens and let coolant pass through and keep a stable operating temperature of the engine.
https://www.2carpros.com/articles/how-an-engine-thermostat-works
https://www.2carpros.com/articles/replace-thermostat
As for the coolant tank being empty. You might have a faulty cap on the coolant reservoir. It might be letting out coolant due to being faulty. Is the cap dot not hold the required pressure it can release coolant out. When that happens it will usually drain thru the overflow tube onto the ground and you might not find any trace as this will happened when the vehicle is driving.
You might want to do pressure test on the cooling system to see where the leak might be coming from. When you do a pressure test, it mimics the pressure the system faces while at operating temperature, which makes it easier to detect leak.
https://youtu.be/W8kra65m15c
https://www.2carpros.com/articles/radiator-pressure-test
I have attached diagrams for your reference.
Please let me know of any questions.
Thank you.
Images (Click to enlarge)
Aug 21, 2021 at 9:05 PM
