Hello all, I was wondering if anyone had any good tips for replacing the thermostat on a 99 Ls400. From what i've seen online, it looks relatively simple but messing with the coolant kind of scares me. Any input is much appreciated, thank you all!

 

Pretty straightforward. Use a factory thermostat and gasket.

 

 

If any concerns, consider assistance.

Depending on condition of coolant, refresh with proper mixture of new Toyota red coolant. Avoid aftermarket green anything.

Inspect your upper and lower radiator hoses and constant tension clamps...probably not a bad idea to replace clamps...do not use aftermarket...

If your ECT sensor (and sealing washer) is original, then replace... this yields real improvements in driveability and efficiency. ...use OEM.

Partially draining the radiator prevents spilling coolant into engine valley.

Mind torque specs on fasteners...

Acquire new plastic petcock with o-ring.

Peruse this forum for other useful information.

 

Attached is the proper cooling system refill procedure.

 

Thank you all for the information, but I have one question. Can I reuse the coolant that is drained out of the radiator since I just replaced the coolant a month ago when my timing belt/water pump was done. In other words, can I just drain half of the radiator then once done with the job, pour that coolant back into the main coolant tank on the left side of the engine? Or does the coolant have to be poured directly back into the radiator? Thanks again for all the help.

 

It can be poured into the expansion tank and reused without issue

 

I would pour it in through the top filler screw first to get most of the air out, but yeah month old coolant is fine to add back so long as you have it in a clean container.

fwiw you'll need a 10mm hex for the top filler screw (iirc) and it has a torque rating. I picked up a 3/8" socket driver with a 10mm hex specifically for this.