Land Rover Repair: temp. guage goes up heater not putting out, head gasket, hotel in branson mo

Question
I just replaced the thermostat in my 2000 discovery II and it seemed to do good...drove from Tulsa to Springfield Mo and when I slowed to get off the highway the temperature guage started going up and the heater stopped blowing warm air...I the radiator never boiled over and had I not loosened the lid on the over flow bottle I probably would not have had to add antifreeze...but I added about 1/3 of a gallon...I thought maybe after replacing the thermostat I had not gotten the radiator topped off...sucks having to fill through the over flow bottle...but started the vehicle right back up and the heater worked and the temperature guage was normal again...did fine on the high way ...then again when I slowed down the guage went back up...but the over flow bottle was full and the vehicle really did not act over heated..again I vented the cap and added maybe another small amount...could I have air trapped in the system? Right now I am setting at a hotel in Branson Mo...seems if I turn the car off and then restart it everything is back to normal...the vehicle has never boiled over or felt hot or acted hot...help!

Answer
Your Rover may have air trapped in the cooling system but it's acting like it has a failed head gasket or a slipped cylinder liner.  There is an article on that on my blog at robisonservice.blogspot.com   You can try bleeding but if I were you I'd prepare for a bigger deal.