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Heater Wont Get Hot

I have a 99 Jeep Wrangler. I recently came to realize that my heater dosen’t work. It use to be quite hot. A while back I put in a lower than stock(195) thermostat 165-185 cant remember which. After i did this and re filled my radiator I noticed my heat was not hot anymore. I just lived with it for a while…but the other day I decided to put a stock thermostat back in to “fix the problem”. afterwords I was shocked to notice that it had not improved the condition at all and it still was not hot. Oh and FYI my AC works fine no problems there. I have been searching forums for answers and haven’t figured it out yet. So im posting up to see what you guys think.

Thanks for your time.


When you did the thermostats you more than like left a bunch of air in the cooling system. Some systems have bleeder screws, so use those if yours does. Or another method is to loosen the upper radiator hose clamp, insert a flat blade screwdriver, and let stuff bleed out there until you get only coolant with no air.

The heater core must have hot coolant that circulates through the heater core in order to have heat in the interior. Find the two heater hoses that go through the firewall and make sure that both are hot. If you have one that’s hot and one that’s cool then coolant is not flowing through the heater core. The heater control valve may not be working or it may be clogged up. If both heater hoses are hot then the problem is with a blend door in your heater ducts under the dash. Low coolant level or an air bubble in the cooling system can also cause a no flow problem with the heater core.

Today I flushed the heater core with my hose. Lots of rusty water came out. I did this till the water ran clear. Then I hooked everything back up and let it ran. The air still didn’t get hot. I then tryed to vent the top radiator hose by loosening the clip to let air out. (I forgot the screwdriver part…is that important?) Anyway after a while with steam continuously pouring out i went back in the vehicle and saw the thermostat was reading what I thought was a little hot (about 230 degrees) so I put the clip back on and parked it. time to go to work. Did I miss something by not using a screwdriver? Should I have let it go longer it wasent in the red yet?