Hi Scotty,
I know there can only be a few reasons for this, but my coolant reservoir tank keeps going down after I fill it back to half way with coolant. The oil isn’t foamy and I can’t see any leaks. I even used the leak tester with the blue liquid you suggested and it stayed blue. Where can my coolant keep going to?
Thanks.
I've seen coolant reservoirs that had small cracks in the bottom that are hard to spot (I was replacing mine which had cracks in it by going to a junkyard, where a couple had the same problem).
Coolant does "expand" when hot then "contract" when cold as long as it's not completely dry every so often you should be fine
You say you can’t see any leaks, and you’ve already tested for a blown head gasket and it passed. How much is the level lowering by and over what period? Have you used a UV dye to trace where it is leaking? You can buy at local auto parts store or Amazon. See video below:
https://m.youtube.com/watch?v=rDuGeQnMOzk&feature=youtu.be
I ordered the leak dye. We’ll see what happens.