I have a coolant leak some where and i can't find it. There is no spots on the concrete. I changed my reservoir cap. I took it to a shop and had them test it for a head gasket and they told me it looked good. The dash tells me it is low on coolant like every 1.5-2 months and have to top it off(and it is low i put about 1/3 of a gal. Every top off.) I was thinking about getting a pressure tester from autozone and some die incase its leaking on top of the block and evaporating away before it drips or can see it, i can see it. Do you guys think of somewhere i should look or to try?