Did an oil change last Saturday, no coolant in oil. Noticed overflow tank was empty. Filled it about an inch above line. Drove it to get to temp, level didnt change in overflow. Car always runs about 173.

Didnt drive it for a couple days after that. Checked the level of overflow tank before I went to work yesterday (drive 50 miles one way) level hadnt changed from when I topped it off (so tank isnt leaking). Checked fluid this morning and overflow is right at the correct mark. So the extra inch I had in the is gone.

No visible leaks, might not even have a leak, not sure how long overflow tank was empty or if thats even an issue for concern.

Gonna monitor daily. Curious what the likely hood it is of the water pump developing leak and how to see that?

 

Check the radiator filler neck they tend to crack an leak under pressure look for wet area or drips under the neck

 

173F is too low. You need a 180F t-stat ONLY AC/Delco 131-158, not like or replaces. Yours is stuck open, should ALWAYS read above 179F after warm up.
Your levels are normal.

 

I had the following problem - the coolant was decreasing, but there was no puddle under the car.
It turned out to be true: the coolant was leaking from the joint of the engine radiator with the pipe on the right below. The liquid was flowing into the inner part of the front bumper (forming a lake there), and during movement it evaporated without getting on the asphalt.
Visually not visible with the hood open and looking from above, the problem was discovered when I bent down and stuck my hand into the bumper from below. Wet fingers stained pink.

one more thing:
a couple of times I encountered the fact that old rubber pipes are intact on the outside, but not sealed on the inside.
The product is rubber and reinforced with textile threads, with age the threads peel off from the rubber and form channels through which the coolant flows out under pressure. The treatment is to replace the old pipes with new ones, not expensive, not difficult.