When the pretty green fluid that resides in your rig's cooling system begins to seep out of the radiator, or if your rig begins to exhibit a tendency to run hot, it's time to break out the tools and swap in a new radiator. For most vehicles, this simple procedure simply requires disconnecting a few hoses and fasteners. No high-tech knowledge is required, and in most cases just basic handtools are needed to complete the swap.
If your rig has a few miles on it, a good rule of thumb is to replace the upper and lower radiator hoses and the thermostat at the same time you swap in a new radiator. After all, the cooling system will be drained of coolant and you'll have the hoses partially removed from the vehicle anyway.
Since ethylene glycol (antifreeze) and cameras don't mix well (and please remember, antifreeze also doesn't mix well with your pets, to whom it is incredibly poisonous, so do not allow it to leak onto the ground where they can get into it), we asked the guys at Attitude Performance to swap out the leaky radiator, worn-out hoses and thermostat in our rig while we shot photos. The total install took less than an hour and a half. Follow along and see how easy it is. This install took place on a 5.0L-powered '92 F-150, but the swap should be similar in most vehicles.
 1. The first step to installing...  1. The first step to installing the new radiator is to get the old one out of the way. First, drain the coolant using the petcock or plug on the bottom of the radiator and then remove the upper and lower radiator hoses. If your rig has an automatic transmission, chances are the radiator also cools the transmission fluid. This means there's inlet and outlet lines running to the radiator that must be removed (inlet line shown). |  2. The next step is to move...  2. The next step is to move the fan shroud out of the way. Ours was held in place by two top bolts and two clips on the bottom. Once the two top bolts were removed, the shroud could be lifted from the clips. The two top bolts also act as a mounting point for the coolant line that snaked from the engine. |  3. Two top-mounted bolts hold...  3. Two top-mounted bolts hold the radiator in position. |
 4. With the two mounting bolts...  4. With the two mounting bolts removed, the radiator simply lifts out of its mount. |  5. We chose to install the...  5. We chose to install the new thermostat while the radiator was out of the truck. Here you can see where the thermostat mounting location is on our 5.0L engine. No great install mystery here; just make sure you install a new gasket before mounting the thermostat and housing. Two hoses attach to the thermostat housing. One is the upper radiator hose and the other connects to the water pump. |  6. Carefully slide the new...  6. Carefully slide the new radiator into position and reinstall the two mounting bolts and the fan shroud, as well as the transmission cooler lines and the coolant line from the engine. |
7. After installing the new upper and lower hoses, fill the radiator with coolant. Do this with the engine running so the thermostat will open and distribute the coolant throughout the engine. This will ensure that it's filled to the proper level. It's also a good idea to install a new radiator cap to ensure proper pressurization of the cooling system. And if your truck's radiator also contains a transmission cooler, be sure to check the transmission fluid level after you've reattached the lines from the transmission to its cooler.
* The engine in your rig runs best at a fairly high operating temperature. Cold engine components wear out faster, and, more importantly, the engine is less efficient. Not only that, failure to reach operating temperature can cause the engine to emit more pollutants.
* Coolant (ethylene glycol) is added to water to improve its boiling and freezing points. Even with ethylene glycol added, high engine temperatures can boil coolant, so the cooling system uses pressure to further raise the boiling point. This is why a good radiator cap is important. It can raise the boiling point by as much as 45 degrees F.
* Temperatures in the combustion chamber can reach 4,500 degrees F., so cooling is critical. If the cooling system fails, the engine can literally seize when the piston welds itself to the cylinder.
* Most modern vehicles use lightweight aluminum radiators. Most radiators for vehicles with automatic transmissions contain a tank that houses a transmission-fluid cooler. In this system, the oil exchanges heat with the coolant in the radiator, and with the air that flows through the radiator. Not only does this system help keep the fluid cool, it also helps it warm to operating temperature in cold climates.
* Fans come in both electric and engine-driven varieties. Both must be controlled so that they allow the engine to maintain a constant temperature. Electric fans are controlled by either a thermostat or an engine computer, while many engine-driven fans are controlled by a thermostatically controlled viscous clutch.