Hey guys,
Had something happen to me yesterday that I though I'd share with the group to possibly help others in the future.

Two weeks ago I was performing my post purchase 90 day inspection on the car and noticed that the coolant level had dropped a bit and was a hair below the "Low" mark. I then inspected all of the visible fittings both front and rear and no signs of a leak were found.
Next I planned to go to the dealer and pick up a gallon of coolant to top it off.

Yesterday I drove across town to the dealer, picked up a jug, stopped off at the store for a gallon of distilled water.
Get home, mix 50/50, and let engine cool for a few hours.
Once it was safe to open the reservoir, I opened the cap and what happened next I wasn't expecting.

As soon as I loosened the cap, the coolant returned to almost the "Full" line.
I had never noticed this to happen in the past (most of my prev cars were BMW's with opaque reservoirs). I did top it off with a few ounces to bring it to the full line.
At least now I have coolant on hand ready to go if I ever need it.
Today when I get home, I'll double check the level to ensure this wasn't a fluke.


So, if your coolant looks low....open the cap and recheck the level.

 

I had the same thing happen but it ended up being I never quite filled it completely. Usually happens if coolant system is opened for service. System has to be treated kind of like an A/C system. Purged of air pockets. You may need to burp the engine. Get yourself an coolant tester to make sure you have a 50/50 mix.

 

Checked again this morning and the coolant was still at the full mark.