2008 crew Max heater problems ,Help .....

My brother has an 2008 crew Max 4x4 5.7L 185K miles on it . The heat is not working at start up but starts 10 min afterwards ( or so ) The temp gauge goes up and down till the heater kicks on. Our guess is thermostat is shot . the fan blows , and you can switch any of the vents you want (from your face to floor to defrost )

thanks in advance .

 

If you think the thermostat may be stuck open then remove radiator cap when motor is cold then start the truck and check if the fluid is moving or swirling. If it is a doing this at first start up when cold the thermostat is more than likely stuck open. I would also check coolant level.

 

@Prostar 190 thanks , overflow Rez was empty added to it . will try opening the rad cap in the morning .

 

Pretty sure this is normal. My '08's heater doesn't start blowing air at a meaningful rate until the air is warm...depending on how cold it is outside that could take 2 minutes or 10. Could this be the case?

 

@TTCrewmax the heat was not coming on at all , found out the radiator was low . Had a new one put on in the summer added coolant and good to go now ! thanks again !!