Radiators on older model cars were made of copper and brass alloys. This made them easy to repair by soldering the cracks or holes that caused leakage.
However, a number of later model cars include radiators with aluminum cores, which have plastic top and bottom tanks. These newer radiators can be damaged by forcing off a hose, over tightening a clip or even by improperly removing the pressure cap.
Damage to the new radiators is impossible for a home mechanic to repair, usually resulting in the replacement of the whole radiator. The one good thing about replacing the newer radiators, is that they are lighter than the old ones and usually have simple fittings which make them easier to remove.
Before starting, disconnect the battery to remove any radiator that has electrical connections.
Drain the radiator
Make sure the engine is cold, then take off or release the pressure cap on the radiator. Some cars have a tap or drain plug in the bottom of the radiator, open it and the radiator should drain.
If no water comes out, poke the drain-plug hole gently with a piece of wire, or unscrew and remove the tap. However, if there isn’t a plug, or you are unable to clear the blockage with the wire, disconnect the bottom hose where it attaches to the radiator.
Drain the coolant into a clean container, then strain it through muslin to remove the rust or dirt so that you can save it and re-use it in the new radiator if its still good. Check the strength of the solution with an antifreeze hydrometer.
While you are disconnecting and removing the radiator from the vehicle, pay close attention to the parts you remove and how you remove them. When installing the new radiator you will be attaching the same parts, in the same way you removed them from the old radiator. You may want to make notes, draw a diagram or even take a picture of the radiator before removing it. This will save you a headache later, if you forget how to attach something or if you forget to attach something.
Remove the hoses
Loosen the hose clips and ease off the hoses by gently twisting them back and forth. Don’t try to pry the them off with a screwdriver: you may wind up damaging the hoses, if you plan to reinstall the current ones. If you plan to replace the rubber hoses, it is much easier to just cut the old ones off.
Oil and transmission fluid cooling lines
Before disconnecting the oil and transmission fluid cooling lines, get another container ready to catch any oil or transmission fluid that will leak out. Next, unscrew both lines from the bottom of the radiator and let the oil, left in the lines, drain into the container. Place plastic sandwich bags over the ends of each line and fasten them with rubber bands. This will keep oil from leaking out onto the ground or garage floor.
Make sure you check, and top off, the oil and transmission fluid when you are finished installing the new radiator.
Clear the way
See if there are any fan-shroud pieces to remove, that will allow you to remove the radiator from the vehicle. However, there is a chance that you will only need to unscrew the radiator mounting clips. After the clips are removed carefully remove the radiator from the vehicle, making sure it doesn’t get hung up on any other parts and that there isn’t anything else attached to it.
Install new radiator
Before starting, set both radiators side by side and check the new one over carefully to make sure it is a match to the old one. Gently guide the new radiator into place, be very careful not to bend any of the cooling fins. Damaged fins will diminish the radiator’s ability to cool the engine properly.
Next install the clips and make sure the radiator is secure. Screw in the oil and transmission fluid cooling lines, being careful to line them up properly so you don’t strip the threads, which cause a leak.
When reattaching the hoses, tighten the clips firmly, but don’t over tighten them, which could cause the clips to cut into the hoses or crush the plastic stubs on the radiator.
Refill the radiator
After you are sure everything is connected properly, fill the radiator with the mixture of coolant/antifreeze recommended by your specific auto company. Also check and refill the oil and transmission fluid as necessary, due to leakage.