How to Replace Thermostat in Lexus IS 250 | More info
is the leading Lexus IS, RX, ES, and GS resource for technical DIY guides. The thermostat should always be in good condition in your Lexus IS 250; learn how to replace it here if it's not! For the full step-by-step article, please visit
The thermostat in your Lexus IS blocks the flow of engine coolant to the radiator when the engine is cold in order to bring the engine up to operating temperature. When a thermostat is worn out, the car's temperature gauge might read incorrectly, and there might be an overheating condition and possibly a leak or two. Lexus owners recommend a thermostat be replaced once the vehicle clocks around 145,000 miles.
This moderately difficult job takes up to an hour and a half to complete and costs from $20 to $30. Take your IS to a professional and you’ll pay around $180 for this repair.
For this job, you’ll need a socket, a screwdriver, pliers, a torque wrench, and a bucket.
Step One - Drain coolant from radiator
The engine doesn't need to be drained of coolant fluid, but it's still a good idea to do so to avoid a mess. Unscrew the radiator drain cock plug at the bottom rear of the radiator. Drain half or one gallon of the coolant and pour it into a clean bucket so that you can reuse it later.
Step Two - Unclip the upper radiator hose from the thermostat housing
The thermostat is placed towards the front section of the engine where the top radiator hose is connected to it. Use a set of pliers or some kind of clamp to squeeze the metal band. The black plastic that the upper radiator hose connects to is the thermostat housing. Coolant will likely drip out of here as you pull it off.
Step Three - Uninstall the thermostat
The thermostat housing is held in place by three bolts. It's shaped like a triangle with a nut at each point. Remove the bolts and extract the thermostat housing.
Step Four - Install the new thermostat
After pulling the old thermostat, align the thermostat valve and insert the new thermostat into the water inlet housing. If the gasket needs replacement, get a new one to take its place. Re-install the thermostat housing as well as the radiator hose.