suddenly the heat are gone now it blows cool air

 

thermostat replacement? start there.

 

My guess would be that you lost some coolant, either thru a leak or being burned, and now there is an air pocket in the cooling system. Check the coolant level, and also check the coolant to see if there is an oily residue on the surface. If the coolant is filled all the way up, then it is most likely your thermostat.

 

coolant is fine so how much is the thermo going to cost estimate

 

wow.. ever hear of google?

 

How can you check for an air pocket? I changed my thermostat but still have no heat.

 

the bleeder valve is above the thermostat. if bleeding does not work. run the engine. there will be 2 hoses at the rear of the motor that go to the fire wall. these hoses are for the heater core. with the engine warm check if both hoses are hot. if they are both hot check the function of coolant valve to the heater core. this valve operates with a cable to the heater control. have someone adjust the heater from cold to hot, watch the valve while they do this and make sure the valve moves. remember dont open any cooling system components when hot. if the valve moves and both hoses are hot u might need a heater core. u can try running a cooling system flush through the system and install new coolant.

 

is your engine warming up completely? how long does that take? if the engine is warming up normally, and your upper hose is hot as well as the lower, then you do not have a thermostat problem. if the t-stat was stuck closed you would overheat fairly quick and boil your coolant. if it was stuck open you would take forever and ever to warm up. if the tstat is fine and you have no hot air then you need to check for a plugged heatercore (not likely) or a malfunctioning blend door (bad lever, blend door motor, or stuck blend door). hope this helps also, make sure both lines going to and from the heater core (the only 2 heater coolant hoses that run into the firewall) are hot.

 

thermostat replacement? start there.