2003 Tahoe Coolant Issue

A month ago I noticed the heat in my Tahoe didn't work well when idle but worked great when driving. Read up on here and checked the coolant. It was very low. I added more coolant and it worked. It started up again and of course the coolant is low again. No visible leaks. Reading on here it could be leaking into the engine???

I am no mechanic (but can do simple repairs) and my husband definitely is not. I have a call to my mechanic. Is this major? Figures we just made the final payment on it last month. :(

the water pump bolts over time will stretch then the gaskets leak. so tighten the bolts on the water pump.. this is most times the mysterious coolant leak . as engine heats up pressure increases then coolant weeps out .. so it evaporates .. as the engine sits the pressure drops so it does not leak out .

the water pump bolts over time will stretch then the gaskets leak. so tighten the bolts on the water pump.. this is most times the mysterious coolant leak . as engine heats up pressure increases then coolant weeps out .. so it evaporates .. as the engine sits the pressure drops so it does not leak out .

Is this something I can do? I have an appointment to drop it off at my mechanic on Thursday to have it looked out. I was fearing the worst after reading about it leaking into the engine.