Will plain water cause your car to overheat?

Answer 1

No, but it will cause other problems.

Water is actually the best possible coolant, better than the normal 50-50 concentration of water and coolant. Here's the problem (or several actually).

1. Water alone doesn't contain any rust or scale inhibitors. Coolant does and will help prevent clogging and deterioration of the system.

2. Water will freeze at 32 degrees F expanding and possibly cracking radiator tubes and in extreme cases even engine blocks.

Coolant isn't expensive so rather than risk damage it's best to follow car manufacturer recommendations for the type and amount to use. Add distilled water to the coolant then forget about it for another year or two.

Cheers