Here's the whole story:


Last spring the heat just stopped being hot. I have a '99 and it was ALWAYS hot, no issues other than having to put the windows down in the winter. NEVER had the needle go over 210 either. Out of the blue Im getting luke warm air.


Flash forward to about 6 weeks back and my needle started edging over 210 and after an hour drive in warm weather when I parked her she puked up about half a cup of dirty coolant. I knew I had a pinhole leak in my radiator, so I just assumed the lack of heat was the dreaded "rotten waterpump", so I went to town.


I replaced EVERYTHING. Literally. Radiator, hoses, thermostat and housing, coolant temp sensor, inlet pipe, waterpump and my heater core was done 2 years ago.


While I had everything off I flushed the heater core just to be safe and clear water came out of both ends. After getting her all back together I was filling and burping and I still coudnt get her hot in the cabin (although the heat core hoses in the engine bay were too hot to touch).


So, after posting here, poking around the internet, etc., I thought I had the dreaded "broken blend door actuator". I took that apart today and its working absolutely fine, albeit a little slow. I took the motor off the bottom of the heater box and I can turn it by hand and hear the door hitting each side of the heater box.


So, what in the actual f is causing me to have luke warm heat? This is absolutely blowing my mind. I don't get whats going on.

Spent another day at it. Literally flushed my heater core forwards, backwards and sideways for a couple HOURS today and I MIGHT have gained a couple degrees in the temp department.


I did have a little bit of debris come out, some little tiny silty rusty crap, but nothing major. The water runs strong and clear and after filling her up and burping her, I still cant get the temp gauge over 177 ish, and cabin heat is MAYBE 65% of what it used to be.


Here's where Im currently at: Either I have a lemon of a heater core OR my t-stat is crap. Whether its not working correctly, its not a high enough temp one or what, I don't know. But I do know that before these issues my temp was ALWAYS on 210, never swayed, but now I cant even get to 180. But for all of you who have heat problems I feel you. I always laughed at heat problem posts here because my Jeep was SOOOOO hot all the time. Not anymore.


I WILL get to the bottom of this one way or another. I just pray it isn't replacing my new heater core.

Thermostat is trashed.

I think you have two issues going on here. First, you need to see if you can manually check the water temp. If it is running cool like that, then I would agree that your thermostat is either messed up or the wrong temp. It could be a 180 degree stat if they gave you the wrong one. The second issue with your heater sounds more like a blend door issue. If water flushes through your core that well, and both inlet and outlet hoses are getting hot, then I would bet you have some sort of a blend door problem. Cycle from floor to defrost and make sure everything is changing well. Take note of the air flow and make sure you don't have debris clogging your evaporator cutting down air flow. Then I would go back to cycling from hot to cold, etc. See if that gives you any clues.

I agree with Suprmn it's the blend door (temp door ) make sure it moves it could be stuck on cold .

pull your blower motor. mine was caked up with tissue from mice. cleaned that out and got some more heat. had to do it again a week later since the damn mice did it again.

i would say if your coolant system is caked red and rusty, like mine was, then you may want to change your heater core.

another thing that did help get more heat out was setting the selector to recirculate. i think it was all the way to the left and not defrost, vent or floor. use the cabin recirc. see how that goes.

100% not the blend door. I pulled the motor off as its super easy to get to right under the dash behind the glove box. There is a plastic arm that goes from the motor into the bottom of the heat box that actually works the door. I can manually move the door open and closed and hear it hitting each side of the heater box. When open, its blowing air from outside. When closed, Im getting luke warm air. I tore the motor apart today (which was running, albeit a little slow and gunked up) and cleaned it up, lubed it and its running great so I reinstalled it. With the key in the on position I can see the motor turning, hear it running and hear the door opening and closing with the air on 1.


Im leaning towards the wrong thermostat after all this. Im thinking that even though the box said 195 that it was the wrong one in the box. Im changing it out again in the morning. I think prior to all this I did have a little crap in the heater core but all the flushing has cleaned it out and not its the t-stat. Companies make mistakes, things get mispackaged, but you never know when someone bought a 4 dollar t-stat and a $10 dollar one and swapped them.


It seems like such a simple system, and TONS of people are always complaining about heat issues which I always thought was odd because my heat was amazing, but MAN its frustrating when everything is new and clean and you STILL have no heat.


Ill post my results with a new t-stat tomorrow night. At the minimum, hopefully some people can read what Ive gone through and get their heat up and running again.

Absolutely. Not just this possibility but the brand new T stat might have been bad out of the box. I have had this happen over the years more times than I can count. Once went through 2 brand new T stats that were faulty from the factory before finally getting the third new one to actually work correctly. Just because they are new doesn't mean they are working as they should.

So I just got done changing out the t-stat again. The one in there said 180 on it, NOT 195 like it should have. New 195 went in, burped her and got way better heat than Ive had in a long time. HOWEVER, with that said, its still NOWHERE near what it used to be. It might be at 75-80% now. And one thing I did notice with the new, correct thermostat in there, the upper hose to the heater core is now much hotter than the return line, which tells me I also have a heater core issue. For some reason the water from a garden hose runs through it clear and strong, but the coolant just isn't getting pushed through it like it should.


It sucks knowing that Ill have to replace the heater core again, but its nice knowing everything else is working as it should AND I now know for sure what the problem is.