I have a 03 four door and I have no heat. About 2 months ago I flushed the system, put a new thermostat in and had heat for a day or two. Last week I took it to my mechanic to get some things taken care of I didn't have the time to fix myself. Fuel pump, wheel bearing, water pump and new intake gasket. I get the car back and heading home it overheats and I blow the water pump gasket out. Take it back and my mechanic tells me the new thermostat wasn't working and it built up pressure and blew out the gasket. I just picked it up and it had heat when I drove off but by the time I got it home, no heat. My 4X4 hasn't worked in about a year and now when I shut the car off I'm hearing a hissing noise. I'm thinking I have a vacuum issues but would this screw up my heat like this?

 

Hmm, sounds kind of fishy, I would be looking for a new mechanic... I doubt he got all of the air out of the system. Take the rad cap off and get the passenger side higher than the driver. A slanted drive way works well. Run it like that for awhile and give it a few bumps on the gas pedal. That usually works for getting the air out.

 

the vac line issue could affect your dampers to control air flow...but you would have heat. you would just be un-able to control to were. did the mech put the thermostat in backwards??

can you see the temp gauge go up to about 210 or so? check the the two hoses going to the firewall...they both have to be hot. you could also have air in the coolant system...although when that happens you can hear a sloshing noise in the dash.

if you have been going to this guy for years...maybe he had a bad day, but i would consider a new mech.

 

I asked him if he put the thermo in upside down. He said it wouldn't fit in upside down. Temp is at 210. Heater core hoses hot and heater core has been flushed and is wide open. I use to hear the sloshing noise but haven't since I flushed it a month ago. New mechanic. Getting the feeling he's a better mechanic in his own mind. Air will jump from the floor to the dash vent all by itself.

 

Either you have a vacuum leak on the HVAC vent position controller or the transfer case vacuum switch has failed and you have oil at the HVAC controller, hopefully not as this will require alot of cleaning to get the oil out and likely will need to replace the entire switch, although I have not tried to take one apart and "fix it"....it may be possible. Take the controller off and check the mult-colored vacuum lines for oil...or if there is any oil present at all on the back of the switch....you have a failed transfer vacuum switch.

Only two reason I can think of for not having heat would be no coolant flow through the heater core or temp door is stuck in the AC or cold position. I think you have verified that you have coolant flow. The temp door is controlled by an electric motor acutator. Bit of a pain to get to, but do a search and you will find the info needed. It is all labor, so it would be expensive to have done. You need to lift the actuator off the temp door privot and then move the pivot with fingers to see if stuck. If not, then with engine runnnig, move the temp control between hot and cold to see if the actuator is working. Be sure to put the actuator back in the correct position...only goes on one way, but it needs to be in the same position as what the HVAC temp selector is at.

Hope this makes some sense....trying to do this quickly.