do the engine gauges still work properly?

Originally Posted by kilosierra

The first time might be right, but isn`t the coolant system pressurized and that because the boiling point independent from the altitude?

No expert here, just guessing.

If it wasn't pressurized then it would leak all over the place. Anything that contains a liquid or gas that is not meant to escape will be pressurized. Balloons, cans of soda, your air mattress. All pressurized.