The Lexus SC 400 is manufactured with a pressurized coolant system that uses a finned radiator to stabilize the engine temperature. This radiator can become corroded or damaged, requiring replacement. The average backyard mechanic can replace the radiator in a Lexus in about an hour.
Disconnect the battery by turning the positive terminal bolt in a counterclockwise direction, then setting it aside. Do not let it touch metal.
Drain the radiator by turning the radiator petcock counterclockwise and allowing the coolant to fall into the drain pan. The petcock is on the lower corner of the radiator; it's a white or black plastic bolt. Uncap the radiator to relieve the negative pressure.
Remove the upper and lower coolant hoses by pinching the hose clamps and working them off the radiator nipples; in some cases the clamps are screw-type and must have their clamp screws turned counterclockwise to come off. The hoses can be worked off the nipples, but leave them connected to the engine.
Remove the fan and fan shroud by turning the corner bolts in a counterclockwise direction, then unplugging the wiring harness adapter by pulling it apart. The fan and fan shroud will pull straight up and out of the engine compartment.
Remove the top radiator mount plate by turning the mount bolts in a counterclockwise direction, then pulling the mount plate free.
Remove the radiator by pulling it toward the top of the engine compartment and working it out of the mount rails. Set the radiator aside.
Replace the radiator with a new unit by sliding it into the mount rails and into position, then reattaching the mount plate and securing it with the bolts by turning them clockwise.
Reconnect the fan and fan shroud by turning the corner bolts clockwise, then reattaching the wiring harness connector by pressing the ends together until you hear a click.
Reconnect the coolant hoses by working them onto the radiator nipples, then securing their hose clamps by pinching them together or turning their screws clockwise until snug.
Tighten the radiator petcock, if applicable, and refill the system with coolant.
Reconnect the battery by turning the positive terminal bolt clockwise until snug.
Crank the motor and continue to pour coolant into the radiator until it can take in no more. Cap the radiator, and check the level of coolant in the reservoir tank often.
