I have been working on my 93 4x4. The truck has always ran cold but heater works fast and fine. Put in a new thermostat, flushed and filled radiator. Yesterday I ran it for the longest yet, about 6 hours at 60mph, with an hour break in the middle. The temp gauge has alway only gotten about an eight above the cold line. During the trip yesterday it got to about 1/2 inch above cold. When I stopped at home, the radiator was gurgling air into the overflow resevoir. No steam just gurgling air. Wondering what it could be?? Also I have bad exhaust leaks in the cat and a tick in the engine.A friend told me to check the rad. cap to be sure it it the correct one and vents at the proper temp. Gas milage is crazy too, in town I get 14-16 on that long trip I got 20. Wondering if that has to do with it FINALLY maybe got to proper operating temp.??