How to Flush Your Jeep’s Radiator

Before you begin the radiator flushing process, make sure you have the following tools and materials on hand:
Safety gloves
Safety goggles
Drain pan
Screwdriver or wrench (to remove drain plug)
Hose or pressure washer
Radiator flush solution
Distilled water
New coolant

Ensure that your Jeep’s engine is cool before starting the process. This step is crucial to avoid burns from hot coolant.
Park your Jeep on a level surface and engage the parking brake.
Open the hood and locate the radiator cap. If the engine is still hot, use a cloth or rag to protect your hand and slowly twist the cap counterclockwise to release any pressure before removing it completely.

Position a drain pan under the radiator drain plug, which is usually located at the bottom of the radiator.
Use a screwdriver or wrench to loosen the drain plug and allow the coolant to flow into the drain pan. Be cautious as the coolant might be hot.
Once the coolant has completely drained, tighten the drain plug securely.

Begin by finding a sealable container large enough to collect the used antifreeze. Position it under the petcock which is located on the bottom of the radiator. On mine, the petcock is located on the passenger side, but the location might vary depending on the source of your radiator (OEM vs. aftermarket). The photo to the left is the petcock. It’s opened by twisting the plastic tab. Remember, it’s plastic, so don’t use too much force on it. Also, I apologize for the poor-quality photo, but I was laying on my back while playing Ansel Adams.

After the radiator has drained, open the radiator cap. Move your bucket under the engine and remove the drain plug on the left rear side of the 2.5L engine block or the coolant temperature sensor or drain plug on the left side of the 4.0L Engine Block (image below).
If you’re flushing the system, follow these steps or the directions on any radiator flushing products you buy. Otherwise, you can skip this section and refill the system.

Refer to the radiator flush solution’s instructions for the recommended amount to use based on your Jeep’s radiator capacity.
Pour the radiator flush solution into the radiator through the radiator cap opening. Fill the remaining space in the radiator with distilled water, ensuring it reaches the maximum fill line. Once the coolant has drained, tighten the petcock and any plugs or sensors you removed. Refill the radiator with water. Turn on the Jeep’s heater and run the engine until the Thermostat opens (the upper radiator hose will become hot). Repeat several times until the water runs clear allowing the engine to cool each time before opening the petcock to drain the radiator.
Reinstall the radiator cap tightly.

Start your Jeep and allow it to run until the thermostat opens. As it runs, the coolant level should drop. This is normal as the system bleeds any air pockets out of the system.

Start your Jeep’s engine and let it idle for a few minutes. Monitor the temperature gauge to ensure it stays within the normal range.
Inspect the radiator and surrounding areas for any signs of coolant leaks. If you notice any leaks, address them promptly.
Once the engine has reached its operating temperature, turn off the Jeep and let it cool down.
Open the radiator cap carefully and check the coolant level. If necessary, add more coolant to reach the proper level.
Recap the radiator tightly.