Although most car owners understand the basics of what it means when the gauges show low oil pressure, check engine problems, or similar warnings, few understand the many things that can contribute to an engine running hot or overheating completely. Before you waste money at an auto parts store buying parts you don't need, here are the things you can check to narrow down the source of the problem.
Check The Radiator And Hoses
The first thing you should do is check the coolant level in the radiator and the overflow reservoir. Both should be even with the "Full" line. If they are below that level, that means you likely have a leak somewhere. Check all of the fittings on the coolant hoses and inspect the hoses themselves. The hoses should all be firmly on the fixtures, the fittings should be tight, and there should be no signs of wear or damage to the hoses. Tighten any loose fittings and replace any lines that are damaged to prevent future coolant loss. Once that's done, you can top off the coolant.
While you're checking the coolant level, inspect the condition of the coolant, too. Not only can low coolant cause overheating, so can dirty coolant. If it's not fairly translucent and free of debris, you should have the entire system flushed and the coolant replaced.
Test The Thermostat
Sometimes overheating is due to a thermostat that's stuck or not opening all the way. The thermostat opens when the engine heats to a predetermined temperature, and when it's open, coolant flows through the system. It's done this way to avoid your engine running too cool due to having coolant running through it immediately when you start it. Luckily, you can test the thermostat, too. Check a service manual for its location and remove it. Before you do, make sure you buy a new thermostat housing gasket so that you can put it back or install a new one.
Once you've removed the thermostat, put it into a small bowl. Pour hot water over it, but make sure the water is heated beyond the thermostat's temperature. For example, if you have a thermostat that's rated for 140 degrees, it should open when you pour water over it that's heated to 150 degrees. If the thermostat doesn't open, that's your problem. Replace it with a new one. If it does open, your problem may be the water pump itself.
Inspect The Water Pump
Your water pump should be located near the back of the engine. Sometimes it's about halfway down and other times it's near the bottom. You can find its location in a service manual. Check the mounting bolts and the pulley on the belt. The bolts should be secure, and the pulley should be free to move. If you're not sure, have a local mechanic check it out for you. You can buy a new water pump from a local auto parts store, too. Bring your old one with you, though, because they may charge a core fee that you can avoid by delivering the old one at the time of purchase.