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jrgman 11-15-2010 05:54 PM

Very Little Heat
I just changed the radiator and all the hoses on my 1999 Wrangler and since then I get very little heat. The blower works good it just does not get nearly as hot as it used to get. I have plenty of anti freeze, the thermostat appears to be working fine and the engine temp comes up as it always has. Any Ideas?

03 RUBI 11-15-2010 07:01 PM

Souns like the "mix door" under the dash isn't working as it should.

jrgman 11-15-2010 07:44 PM

I'll check it out. Some one told me the heater core core supply may be coming in on top rather than the bottom.

Jerry Bransford 11-15-2010 07:51 PM

The heater core uses two slightly different hose sizes so it wouldn't be easy to get them reversed. Besides, I don't see how reversing the hoses could make it run colder unless doing so clogged it up by forcing gunk back into it. If your engine is running at the normal 210 or so temperature and the blend door is working, odds are very good that the heater core is clogged with gunk which can be flushed out by vigorously back flushing it with a garden hose. VIGOROUSLY... use some pressue and go back & forth until the water flows freely through the heater core. :)

Work4Mud 11-15-2010 08:24 PM

Probably not the same as your issue but somewhat related...I recently got the bushwacker vent scoop and since slapping it on the hood I have been getting blazing hot heat! Like an incredible difference thats very noticable. Not sure it would do anything for you but just wanted to share.

98tj25l 11-15-2010 08:46 PM

An easy way to check if your heater core is clogged is by letting the Jeep get up to running temperature, and feel both hoses leading to the heater core. If they are both hot, than you are getting flow through the core. If one is hot and the other is noticeably cooler than the other your core is clogged up. If that's the case do as jerry suggested and flush it out.

tomslusher 11-15-2010 10:12 PM

A week ago I did a water pump R&R and today noticed this same exact thing. Much less heater core heat, engine temp is normal, ect. I called my genius mechanic buddy and he told me the check the coolant level (could be a big air bubble in the line, but doubtful after 1 week) and if it is OK then flush the heater core with a garden hose, both ways. I did check the blend door and can hear it clunking in both directions and when moved to the cool postiion, it cools just fine. I haven't tried the flush yet but hopefully that will solve the problem. Please let me know if it works for you if you get to it before me.

By the way 98TJ, which would be hotter, the one coming from the thermostat cover or the water pump?



98tj25l 11-15-2010 10:47 PM

The hose coming from the thermostat housing should be hot.

huntersemt10 11-16-2010 06:10 AM

i noticed sludge in my radiator. i need to flush it. i too have very little heat . i flushed the core until the water ran clear , i think i neeed to flush the radiator and add new coolant all the hoses are hot . when i flushed it i had heat for a day or two , but now its not hot at all

jrgman 11-16-2010 06:36 AM

Thanks, Now that I think about it I did not hear the blend door slam shut as usual. It is normally very noticeable and I don't remember hearing it. If not that I will flush the core on a weekend project.

98tj25l 11-16-2010 11:19 AM

Huntersemt, When my system needed a good flush I bought Prestone Super Cleaner, and a prestone flush & fill kit. Follow the directions for the cleaner, then do a back flush of the entire system. Fill it up with new coolant, and distilled water (Don't use tap water!). Then you'll be ready for winter. After I did this I was blowing 150 heat at the vents. Another little tip, the petcock on our radiators is plastic and prone to break (mine did). When you drain the radiator instead of using that, just disconnect the lower radiator hose....Good Luck!

jrgman 11-17-2010 06:24 PM

It apparently is the mix door. It is not moving at all when I change from cold to hot. It normally makes a fairly loud sound. I am looking for my Haynes Manual. What is the best way to get to it and how is it controlled?

tomslusher 11-22-2010 08:08 PM

Finally got around to flushing the heater core. What came out was a gross mixture of orange/rustish color. Two weeks ago I put all new coolant in (minus what was in the heater core, I guess) with green stuff. You think it would have mixed at least some. The core must have been plugged pretty good.

I now have a heater that will melt my shoes. Just in time for 10 degrees F. temps in the morning.

Thanks for the help,


98tj25l 11-22-2010 10:15 PM

Glad to hear you got your heat going! Now you'll be nice and toasty all winter!

TJNewbie 11-23-2010 01:52 AM

I don't have much heat either, but I notice that the temps never get above 180. I live down in the south, is it possible there's 180 degree thermostat in my tj?

jrgman 11-24-2010 06:13 AM

Mine turned out to be a plugged heater core caused by the radiator change. I flushed it and the heat is better I need to flush some more.

TJNewbie in LA It could be you can never have hotter air than your thermostat.Typically the outlet temp runs somewhere around 10 Deg Delta T. If you have better consider it a good thing. It means that the water temp and the air temp have a 10 deg approach or difference. 180 deg water = 170 deg air etc. Sometimes it's better than that.

TJNewbie 11-24-2010 11:58 PM

ok thanks for the info

huntersemt10 12-10-2010 06:49 AM

im bangin my head against the wall . i flushed the core . all the hoses are hot to the touch. like really hot i cant hold em , i checked the connections under the dash . everything moves, theres vacuum for the vents all the vents work. i changed the thermostat , flushed the radiator . but heres the thing . i put in all antifreeze i didnt put 50/50 mix with water , even though it says do not add water . should i have put water in too ? i spent half the day with this thing yesterday . i get some heat when i turn down the fan , but as soon as i get goin it gets cold .. blend door maybe .. please advise

98tj25l 12-10-2010 11:00 AM

Hunter, let me make sure I understand this...You filled your entire system with pure antifreeze? Are you sure that you used pure antifreeze, and not a 50/50 pre-mix? If your system is all antifreeze then yes you should have added distilled water to get the right ratio. Having all antifreeze in your system will cause corrosion, strain the water pump, engine wear, and it actually raises the freezing point. Now, your right the blend door seems like it must be the culprit. So get your antifreeze ratio set to the right mixture, then get working on fixing the blend door.

huntersemt10 12-12-2010 02:44 PM

NOOO ,, I put in 50/50 but should I have added more water . does water create more heat when mixed correctly . bottom line is everything is hot to the touch, every hose... . and the radiator was flushed out . the blend door has got to be the bandit in this .. thanx for the reply I really appreciate the help if you have any other help for me please let me know . :banghead:

Jerry Bransford 12-12-2010 02:45 PM

50:50 is fine. More water cools the engine than more coolant does but 50:50 is a pretty optimal mix for most conditions.

jsahara00 12-12-2010 03:00 PM

All I did was a quick heater core flush, water barely pushed out the exit at first... after that was cleaned out it feels like an oven again.. it may not be ur issue but its worth a shot and not a bad idea to have a full fluid flush anyways

briancash1013 12-12-2010 03:04 PM

Not to highjack or anything but I just flushed my heater core yesterday and it still only blows warm air. I'd put money on the blend door, now if I could just find it to check it

Jerry Bransford 12-12-2010 03:09 PM

Did you flush your heater core in both directions? Otherwise I'd guess the blend door too.

huntersemt10 12-13-2010 08:04 PM

the culprit .... the blendoor .. i took of the acuatior it was stuck .. gun lube and it works fine.. i move the door my self , heard a thump ..... HEAT . I HAVE HEAT .. THANX EVER:)YONE FOR THE TIPS .

jrgman 12-14-2010 06:10 AM

Exactly where is the blend door and how hard is it to get to. I flushed my heater core and the air got a little hotter but I can't hear the blend door move as I thought I use to.

98tj25l 12-14-2010 09:16 AM

The blend door actuator is located slightly behind the foot vent on the passenger side, and it's held in place by three screws, It's right out in the open so it's very easy to get to.

Huntersemt10, glad to hear you got your heat going!

briancash1013 12-15-2010 03:36 AM

My actuator is turning but I still only get warm air. How far should it turn when it is going from cold to hot? And i can hear the door actually close like i have read everyone talking about. I have already flushed the heater core.

huntersemt10 12-17-2010 06:49 AM

i have the haynes manual for jeep wrangler .. it sucks .. i need the a book for the 2.5 jeep wrangler with indepth pics . i still need to get a vacuum leak under the dash for hotter heat . i have heat but its not the heat i had last winter. when i let out some pressure from the driver side vaccum lines under the dash it gets really hot . when i slightly put the red vaccum line in slightly the heat gets really warm .. its ok . but i what my africa heat back..

jasonwrangler 12-17-2010 10:51 AM


Originally Posted by huntersemt10 (Post 929360)
i have the haynes manual for jeep wrangler .. it sucks .. i need the a book for the 2.5 jeep wrangler with indepth pics . i still need to get a vacuum leak under the dash for hotter heat . i have heat but its not the heat i had last winter. when i let out some pressure from the driver side vaccum lines under the dash it gets really hot . when i slightly put the red vaccum line in slightly the heat gets really warm .. its ok . but i what my africa heat back..

vacuum only controls how the air is flown not how warm the air is.

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