Coolant leak!

[Rob175]

Also check the coolant expansion tank in the trunk. They are notorious for developing "spider cracks" that only start to leak as the coolant gets hot and the coolant system pressure builds up. When cold the "spider cracks" are almost impossible to detect.

Make sure you remove the truck carpeting completely and if you have a false raised trunk under the carpet make sure you remove that too. You need to get down to the metal trunk bottom. You might find (as I did yrs ago) small pools of coolant sitting there, ready to slosh around and find gaps to drip onto your garage floor.

Long story short, 10 years ago I replaced my then 15 year old coolant tank and water pump once I discovered pooled coolant in the trunk and spots on my garage floor.