Why the Radiator Cap is Important

Water boils at about 212 degrees Fahrenheit, but many cars are designed to run cooling system temperatures well over 220. The question is, how is this possible?

Coolant - A mixture of water and antifreeze, usually ethylene glycol based that raises the boiling point.

System Pressure - By having the system closed and pressurized, this also raises the boiling point.

Today's article is about the system pressure, most notably the radiator cap. Several years in automotive repair has showed me the same thing over and over....THE RADIATOR CAP IS CONSTANTLY THE ROOT OF MANY COOLING SYSTEM EVILS! It is overlooked by car owners and "professional" technicians alike.

As I have stated in previous articles, the purpose of this blog is to explain how things work in simple terms and why they are important, not to teach auto repair online, so here goes:

At some point in your life, you have seen a car with the hood up and steam pouring out from under the hood. What happens next? You might have seen someone(or have been the unfortunate soul) ignore the warning that says CAUTION:DO NOT REMOVE WHEN HOT! Why not? Well because one, the darn thing is hot to the touch and it will burn you badly! Second of all, if there is any coolant left, as soon as the system loses what pressure is has, the coolant will boil over immediately! Even when the cap is failing, it still usually will hold some pressure. If you overheat, just plan on letting the car cool off. If you do manage to get past the first two obstacles, adding cold liquid to an overheating car is a recipe for further damage that I will cover in future articles.

The moral of the story?
Inspect your cooling system annually or have it inspected by a trained professional, change your fluids, belts, hoses and thermostat BEFORE the manufacturers recommended interval. Yes, this costs money, but most people run out of warranty before car payment. You would also be surprised what a warranty will NOT cover due to owner neglect. And most importantly, DO NOT FORGET THE RADIATOR CAP. They range from $8 on up, but a faulty one could lead to thousands in avoidable repair.