How to Change the Radiator in a GMC Truckby Eli LaurensUpdated July 06, 2023
General Motors pickup trucks use reciprocating cylinder technology that requires a liquid cooling system, and the primary radiator for this system can break down and require replacement. The average backyard mechanic can replace a radiator in about two hours.
Things You Will Need:
- Socket set
- Drain pan
- Vice grips
1. Drain the coolant into a drain pan
Drain the coolant into a drain pan. Most models of GMC radiator will have a drain plug on the lower left or right of the radiator body. This plug can be loosened by turning it counterclockwise until coolant comes out. It may not be necessary to totally remove the plug, just loosen it. Uncap the radiator and release the pressure on the radiator to drain it completely.
2. Disconnect the coolant hoses from the radiator
Disconnect the coolant hoses from the radiator. There are two hoses, upper and lower, that will come off once their hose clamps are loosened with a screwdriver or vice grips. The hoses might have become stuck due to age, and may need to be cut and replaced with new hoses. Some coolant might drip out when the lower hose is uncoupled.
3. Remove the fan shroud and fan
Remove the fan shroud and fan. There are four screws on the back, and once freed the shroud should slide out towards the top of the radiator. The wiring harness will disconnect at the adapter plug at the fan. If the fan is mechanical, then it must be unbolted at the fan clutch and slid off towards the front.
4. Disconnect the oil cooling lines, if so equipped
Disconnect the oil cooling lines, if so equipped. There will be an upper and lower line, and they unbolt with line nuts in a counter-clockwise direction. Some oil might drip out, so have the drain pan handy.
5. Remove the old radiator
Remove the old radiator. Unbolt the top radiator plate, if necessary, and slide the radiator out towards the top of the engine compartment.
6. Replace the old radiator with a new one
Replace the old radiator with a new one. Slide the new radiator into place, and attach the top radiator mount plate. Reattach the fan and fan shroud, and replace the oil lines and hoses.
7. Fill the new radiator with 50 percent water and 50 percent coolant
Fill the new radiator with 50 percent water and 50 percent coolant. Once the radiator is full, crank the truck and continue to pour until the radiator can take in no more coolant.
Tips and Warnings
Use distilled water, not tap, for better radiator protection.
Do not allow coolant to remain where animals can get to it.
Video showing how to replace a GMC radiator:
Comments on this video:
- Awesome video that diagnosed my problem, exact same crack point as you but mines twice the size... And now I know what I'm getting into and have no worries behind it! Thank a lot Scott!
- Awesome video. Paid $200 for parts, some tools and spent about 2 hours working on it. Better than the $600 that the shop quoted me. Thank you so much!
Eli Laurens is a ninth-grade physics teacher as well as a computer programmer and writer. He studied electrical engineering and architecture at Southern Polytechnic University in Marietta, Ga., and now lives in Colorado.