just had the water pump replaced. two days after i am still topping off the coolant level. no coolant leaking, but every time i warm up the engine and let it cool to add coolant the level drops a couple inches. the upper rad hose gets hot so i know the tstat is working. both hoses to/from the heater core are hot. any suggestions?

 

so are you getting heat?

if you have to keep adding coolant and its not leaking, it could be a head gasket.

you could have an air pocket in your engine and its taking a while to get it out. did you run the truck with the rad cap off for a while after you replaced the stat.

 

A good trick to do is jack up the front of the truck and make sure your heater control is on the hottest setting. Then get into your truck carefully, use jack stands, and rev your truck up around 2-3 and watch your where your radiator cap goes, make sure its off. If you have air you will see it spirt up and bubble. Do that for 15 min then add more coolant. Make sure you squeeze your upper heater hose, the one that goes to the thermostat, to try and push as much air as possible out. I know a trick that some people do is that they drill a small hole in the thermostat to let air get by. You should be good after that. Did you flush your heater core? takes 15 min

 

Are you seeing your resevoir level rising? You might be adding and adding, and your resevior is filling and filling.