[grandpas wagon]

First, do a pressure test............you can rent one free at AutoZone or O'Reillys. You may have a bad coolant cap.

Have you bled the system properly?

 

[grandpas wagon]

Water boils at 212 degrees. For every pound of pressure you put water under, it will raise the boiling point approximately 2 degrees. So a good 15 pound radiator cap will raise the water's boiling point 30 degrees from 212 to 242 degrees Fahrenheit. Add 50% of coolant and the boiling point of the mixture is well over 265 degrees


steam can't be pumped by the water pump, that's why the coolant needs to stay in a liquid form. So if the coolant turns to steam too early because of a bad radiator cap or a weak mix of coolant and water, the car will overheat at lower temps, which explains when you are in an extended stop in traffic on a hot summer day.

Also, even if your not pumping steam through the waterpump you will quickly trap air in your cooling system which can cause your car to overheat.

THAT BEING SAID...



I totally agree with this as well. While a bad cap isn't necessarily contributing to the heat problem. It def isn't helping. Keeping the coolant system under pressure just helps keep the car from overheating.

If he has never replaced the cap it's probably a good idea to and to clean off the crud around the cap on the overflow tank.

It is a quite evident our new member of just a few months took high school physics while our 10 year member didn't or forgot this basic principle. Thanks for setting the record straight with your fine explanation..................Yes, a bad cap can and often does cause overheating.