88 Bronco II losing coolant

[GMWolfie]

I seem to have a perplexing problem. I recently had my 88 Bronco II repaired and asked that the cooling system be checked as I was losing coolant but saw no leaking. I was told that the engine was pressure checked and that there was "some seepage" in the radiator, hoses and possibly the water pump, but not enough to warrant any real worry. Today, I saw the temp gauge going up and checked the level to find I needed about 3 quarts of coolant!
Again, I see no leaking and am hoping against all hope that the head gasket isn't the culprit.

Suggestions? The temp sending unit and sensors were replaced as well.