Cracked Radiator
 

So car was using almost a quart of coolant every 60 miles. Took to dealer, cooling system and block held pressure which agreed with my observation that the hoses were hard when hot.

No detection of coolant in exhaust or oil. No observed leaks. Car runs super smooth.

Final step was to add fluorescent dye to coolant. After about 50 miles I can now see it on the side of the radiator, cracked either top hose fitting or near mounting bracket.

Odd thing is that it was losing that much coolant, but only while moving (maybe sealed when sitting still, but leaked under "vibration"). You would also think we could have seen it on the underside of the car, but no.

No wonder the service manual coolant loss troubleshooting section ends with "replace radiator" if all other sources are eliminated as culprits.

Odd you never saw any steam......