How to Replace the Thermostat
1990-1994 Lexus LS400
This one is pretty simple and you don't need any special tools. The thermostat and gasket should cost less than 20 bucks.
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1) Unscrew and remove this cover.
2) Remove this 10mm bolt to remove the main air intake.
3) Using a pliers, unscrew the radiator drain cock and drain some coolant. Draining about 1/2 to 1 gallon should be fine. You need to drain some coolant out otherwise you'll end up with a big mess when you disconnect the radiator hose. Note: You don't have to have your car on ramps, this is just the picture I had.
4) Loosen the clamp and then disconnect the water inlet hose.
5) Remove the two 10mm nuts and then remove the water inlet.
6) Remove the old thermostat and gasket. Install a new gasket (Part #16325-62010) on the new thermostat (Part #90916-03084). Then align the jiggle valve of the thermostat to the top of the housing and insert the thermostat into the water inlet housing.
7) Put everything back in reverse order of removal. The nuts for the water inlet should be torqued to 13 ft-lb (185 kg-cm, 18 N m). Close the radiator drain cock and refill the engine coolant back into the coolant reservoir.
8) Start the engine and check for leaks.
LexLS.com Notes: Thanks for contributing the pics Thuan! I added a few pics and the instructions for this tutorial based on the original posting of this tutorial on LOC and the repair manual. Since you need to drain the coolant it would be wise to combine this with something else, like a coolant flush.
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