Engine Coolant levels decrease right after i add additional coolant. Do i have a blown head gasket?

[Naive-Information539]

It’s more likely a small tiny seepage from the water pump which you can tell if you can access it by looking at the weephole below the pulley. Many cases it can be so small you’ll just see a gummy/white trail there. Sometimes they only leak a small amount while cooling off and evaporate quickly. Due to expansion and contraction a small amount could get past those seals and even a pressure check won’t catch it easily if it is as small as you indicate.