We have an X5 that continues to run hot after I've replaced the Water Pump and Thermostat. I've found that I needed to burp it and have done that several times, and I either loses some coolant and runs  hot again.  I refill and burp, and it still runs hot if it sits at a light on a warm day.  I need help to figure out what I'm doing wrong. Do I need to retrace the lines for leaks? I'm doing something wrong, and think that it's something simple.

Morning Larry

Welcome to the Forum

I take it the new thermostat is correct and working OK ? If you are not finding puddles under the car then check the carpets inside (hope there aren't any internal leaks. Hopefully there are no wet carpets, then I would check the areas that can swallow water and boils it off. So simple things first is the expansion tank cap sealing properly, the turbo runs Fliping Hot and any coolant leak around the turbo will be boiled off but it should leave traces, white residue so check all the hose connections carefully. 

The one you don't want to think about is head gasket but a sniff test by a garage will tell you if there is any exhaust trace in the expansion tank, fingers crossed there aren't any.

Good Luck

Dave

Is there still air in the system? You mention burping. I'd try a pressure test on the cooling system. Will show up any leaks.