Have a 2001 SSEi with 224k miles. LIM gasket was replaced at 85k miles. Coolant was last flushed about 18 months ago, with the reservoir being overfilled as I put too much in it but was to lazy to remove excess.

Went to check trans fluid today, and happen to catch the coolant overflow tank is bone dry. I do not believe there is a crack in the overflow tank. I have not noticed any coolant leaking anywhere, no coolant smell, and temperature running just fine at 200 degrees in hot weather.

Heading to get some coolant and distilled water later tonight; thought I would post this and see if anyone had any thoughts on where the coolant went...

Crankcase, cabin, or the ground. Job 1 should be to rule out #1, it'* easy though, just pull the dipstick while running.

Next job should be to see how much coolant is being lost and to start looking for puddles.

Replaced the missing coolant earlier this morning. Radiator took about a quart directly, then filled the overflow.

No signs of any issues, I replaced all the hoses 18 months ago when I flushed the coolant. Water pump is original, but no signs of seeping. Guess I will have to go find my radiator pressure tested buried away somewhere.... My guess is another LIM gasket failure, or water pump going and I just don't see the leak....

If its an external leak, coolant always leaves a residue. It doesn't exactly evaporate over night.

As Randall already said, crankcase or cabin. But if you have a good nose, you could smell the sweetness inside.

I have a good nose for coolant with multiple heater core failures in my past. Zero smell in the cabin. No sign of smoke out the tailpipes, no milky buildup on the oil fill cap, and no rise in oil level. Worse thing, it seems to lose the coolant quickly. Did a 80 mile run today, level went down about a 1/2 inch in coolant overflow- but that could be do to overflow refilling the radiator.

It might be a good idea to take a close look at the coolant elbows too, just to rule them out for the time being.

You know how those can go...

Methinks, your brother-in-law is screwing with you,

You might want to check the block off plate on the DS end of the lower intake manifold
the exhaust pipe is right over it making it hard to see.
I have seen it leak then it disappears but you can see coolant down farther accumulate on the transmission.