Despite costing a mere couple of bucks, your radiator cap is one of the most important parts of your 4WD. They do not last forever, and can 'let go' without much notice. Not a whole lot of fun if you are in the middle of the bush.
The cooling system for your 4WD's motor plays a massive role. It regulates the motors temperature by allowing it to warm up as required and then stay under a certain temperature. If its not working properly, the results can be devastating and extremely expensive.
What does a radiator cap do?
A radiator cap regulates the pressure inside your radiator, which in turn allows the coolant to heat beyond its normal boiling point. If your coolant is allowed to boil, you can do huge damage to your motor.
A radiator cap that is not working properly will not regulate the right pressure in your cooling system. You may have noticed that coolant will move from the radiator into the overflow tank when the vehicle is warm and then back again as it cools down; this is the work of the humble radiator cap.
Where can I get one from?
You can buy radiator caps from almost any automotive store including Repco, Supercheap Auto, Auto one, Autobarn and of course your genuine distributor (Toyota, Nissan, Isuzu etc).
Grab a spare radiator cap
Even a genuine radiator cap should cost no more than $15. Keep it in your glove box or spare parts tray. If you are having cooling issues, a radiator cap is a common faulty item. Look for damage to the rubber or spring, and if its not looking healthy, chuck the new one in!