Table of Contents
Getting the Job Started
Replacing a radiator on a Lexus IS250 can seem daunting, but with the right approach it becomes a manageable task. The key is to work from the engine bay, avoiding the need to remove the front bumper cover. Begin by ensuring the engine is completely cool; this protects you from hot coolant and makes the radiator cap easier to remove. Turn the cap counter‑clockwise, pressing down if necessary until it clicks and then pulls off. Set it aside and move on to the next step.
Draining the Coolant and Removing the Old Radiator
Under the vehicle, a shield typically covers the radiator area. If present, partially or fully remove it with a 10‑mm socket and a trim tool to access the drain plug. Turn the plug counter‑clockwise to allow coolant to flow out; let it drain completely before re‑threading it snugly. Next, remove the radiator cover, which is held by push clips. Use a trim tool to pop each clip and lift the cover away. The air intake duct, clipped on one side and bolted on the other, follows the same removal process: unlock the push clip, then loosen the 10‑mm fastener (or Torx if it has been replaced).
With the cover and duct out of the way, detach the upper radiator hose by loosening its clamps and pulling it free. Remove the coolant overflow cap and set it aside. Two 10‑mm bolts on either side of the radiator support must be removed, and the wiring harness is freed by pinching its clip with needle‑nose pliers. Once the harness is out of the way, the radiator can be lifted out of the engine bay. Before removal, unplug the fan connectors and pop the wiring retainers with a trim tool. The lower radiator hose is released by pulling its clamp away, then the hose itself is slid out. A drain pan should be placed beneath the radiator to catch any remaining fluid.
Installing the New Radiator
Position the new radiator by sliding it into place, taking care not to damage the fins or any nearby components. Install the top rubber mounts, ensuring the pointed ends face upward. Align the AC condenser with the radiator and secure it with at least one mounting bolt, tightening only enough to avoid cracking the plastic. Repeat on the opposite side. The radiator support is then lifted, the radiator is pushed back toward the engine, and the support is re‑bolted. Reattach the lower radiator hose and clamp it securely—tighten only an eighth to a quarter turn to prevent over‑tightening, which could damage the hose or radiator.
The fan assembly requires a few more steps. Pop the lower hose retainer tabs, then install the new fan assembly by sliding it into place and clipping it onto the radiator. Re‑attach the wiring harness and plug in the fan connectors. The overflow tank is secured by sliding the J‑nuts over the new assembly and tightening them. Finally, re‑install the coolant overflow hose and cap, ensuring a snug fit.
Reassembling and Bleeding the Cooling System
With the radiator and fan in place, re‑install the air intake duct and cover, securing all push clips and bolts. The radiator cap is then replaced and locked in. To fill the system, use a spill‑proof funnel positioned at the highest point of the cooling loop. Pour coolant into the funnel until bubbles cease, then start the engine and let it reach operating temperature. Keep the heater blower on low to draw hot air from the heater core, confirming that the core is filled. Once the thermostat opens and no more bubbles appear in the funnel, the system is fully bled. Remove the funnel, reinstall the radiator cap, and the radiator replacement is complete.
Final Thoughts
Replacing a radiator on a Lexus IS250 is a straightforward process when approached methodically. By working from the engine bay, carefully draining coolant, and methodically removing and reinstalling each component, you can restore the vehicle’s cooling efficiency without unnecessary complications. The key lies in patience, proper tool use, and attention to detail—especially when handling hoses, clamps, and electrical connectors. With the radiator back in place and the system bled, your Lexus should run smoothly and reliably for years to come.