My 2006 GMC Yukon XL Denali 6.0L is over heating and the interior heat does not work. Is this the water pump or is there a thermostat sticking? I'm in the mountains and thought maybe something was frozen the vehicle water temperature rises fine however there is no heating in the cab. It is ususally parked in garage but has been in below zero temperatures for several nights. Is it possible a line is frozen.

What is the optimal operating temp of a 2006 yukon xl denali 6.0 motor. A friend stated that if the t-stat valve is open is will have more power but I want/need more fuel efficiency!!!! So its got 80k miles should I just change it anyway? the temp is running 150-under 200 on gauge?

There is a fitting on the intake that feeds a pipe/hose combination that gets clogged real easy by the coolant that GM uses(coolant is called DEXCOOL) if you don't flush your cooling system every 25-30 thousand miles or every 2 years this stuff cakes up the cooling system and causes all sorts of problems from leaks to overheating etc,etc,etc,...Make sure your cooling system is full while running engine and that the coolant is flowing thru the system.at normal operating temp.your upper and lower radiator hoses should feel the same temp.

Overheating can be caused by stuck shut t-stat but u would have heat at-stat stuck open no overheating and no heat. a waterpump that the impeller broke or rotted of can cause your problem but rarly seen does your fan work or any leakage or low coolant can cause air pocket and overheating no heat. let me know and we go foward