After spending several hours looking for a bleeder valve that doesn't exist, and not finding any useful information online, I wanted to put a guide out on intercooler coolant changes on 2015-2026 IS turbo models. I ended up vacuum filling it myself but confirmed the factory procedure afterwards. I was only able to drain about 1/3 of a gallon from the stopcock, and roughly the same amount went back in.

The factory method is to fill the reservoir and then manually cycle the intercooler water pump using their computer—1 minute on, 1 minute off, repeated three times—to purge the air. They also say you can cycle the water pump by revving the engine to 2,000 RPM for 1 minute on / 1 minute off, three times. Recommended replacement interval is 100,000mi for first change then every 50,000mi.

For what it’s worth, there are no bleeder valves on the main coolant loop either. Although NX turbo models with the same 8AR-FTS engine have bleeders on both the intercooler and radiator loops, the IS does not—so don’t waste your time hunting for them.