How to Unclog a Radiator

A vehicle’s radiator is vital to protecting the engine from overheating. In extreme cases of overheating, the engine’s block or cylinder heads can crack and gaskets can fail. Within every radiator is a series of cooling fins arranged in rows. As the water and antifreeze within the radiator passes through these fins, heat is dispelled. These fins are susceptible to clogging, particularly if antifreeze is not used for a long period of time. Antifreeze raises the water’s boiling point and reduces the water’s freezing point, but also features a number of chemicals designed to prevent rust. Rust particles and other debris will eventually clog the radiator. Thankfully, removing most debris is a simple task that can be performed once the radiator has been removed from the vehicle.

Things You'll Need:

• Screwdriver
• Wrench
• Flare nut wrench
• Garden hose

1. Remove the radiator cap

Remove the radiator cap by pressing down on the cap while simultaneously twisting the cap in a counterclockwise direction.

2. Drain the antifreeze from the radiator

Drain the antifreeze from the radiator by removing the drain plug located on the bottom of the radiator with a wrench.

3. Remove the upper and lower radiator hoses

Remove the upper and lower radiator hoses. Each hose is secured to the radiator with a single hose clamp. Each clamp is held in place with a single screw. Loosen the screw on each hose clamp with a screwdriver until the clamp can be slid down the hose, then pull the hose away from the radiator.

4. Remove the transmission cooler lines

Remove the transmission cooler lines, if the vehicle is equipped with an automatic transmission. The two cooler lines are located on the bottom of the radiator. Each line connects to the radiator with a single nut, which is integrated into the line. Loosen each nut with a flare nut wrench, then pull the cooler lines away from the radiator.

5. Remove the radiator from the vehicle

Remove the radiator from the vehicle by removing the radiator’s retaining bolts with a wrench, then by lifting the radiator out of the engine compartment. A single retaining bolt is typically located at each corner of the radiator.

6. Turn the radiator upside down and place the top of the radiator on a flat surface

Turn the radiator upside down and place the top of the radiator on a flat surface. Insert a garden hose into the outlet that the lower radiator hose is attached to, then turn the hose on until the water that runs out of the radiator is clear. As the water passes through the radiator, it will remove the majority of the clogs and deposits within the radiator’s fins.

7. Turn the radiator over and insert the garden hose

Turn the radiator over and insert the garden hose into the outlet that the upper radiator hose is attached to; then, to complete the process, turn the hose on until the water that runs out of the radiator is clear.

Video showing how to flush a radiator:

Comments on this video:

• I have watched a ton of radiator cleaning/refill videos, everyone has their own opinion on how you should do it. It’s nice to see that these guys are keeping it real.
• Simple green is my go to cleaner. I like that it gets the job done without all the toxic odors. A big plus is that it doesn't make my daughter or my dog sick to be around it.