It getting closer to cooler weather and my 98 tj 2.5l heater is not blowing hot air at all..the blower motor seems to be working great cuase it blows out strong amount of air ,however it's just outside air I guess. I don't have an ac on my jeep and I am actually ok with it during the summer but I dont do as good with the cold weather and would love to get it working. Any help would be appreciated . Would it be a sensor or heater core . Thanks in advance
Heater not blowing hot air
- Thread starter Mesjeep98
- Start date
There are a few different potential causes. First, the T-stat may be defective and the engine does not come up to operating temperature in cooler weather. The heater core could be plugged or coated with insulating layers of crud. The climate controls may be inoperative. I would suggest you start with a good cooling system flush and see if there are restrictions in the flow in and out of the heater core. Use a good quality flushing agent and follow the instructions. Flush that sucker until it flows clean as a whistle. If your T-stat is old, don't be afraid to replace it as a maintenance item. They don't last forever. I had a neglected Jeep. I had to replace absolutely everything in my heating/cooling AC system. Even the knobs.
it has not worked since I purchased it a few months ago so I do not know how long it hasnt worked
i would start with the blend door actuator first is a shit load easier to check than all the work to flush a cooling system
Even if the heater worked perfectly, a 21 year old rig will surely benefit from a good flush. I just installed a new to me engine with ridiculously low miles. While engine oil pan and innards were very clean, the water jacket was full of crud. I used chemical flushes one a week for three weeks, each time I flushed it about 10 times. I got tons of crud out of it. The third week on about the 30th actual purge cycle I could then declare the block clean. I will run it for about three months and flush again. New vehicle, drain everything and fill with new lubricants. No one ever suffered from good preventive maintenance.
Before I start putting in new radiators and turbo props I would just feel the heater hoses coming out of the firewall. If they both get good and hot then the problem doesn't require a new engine. 
it has a brand new radiator,water pump. Only thing right now that doesnt seem to be working is the heater.Before I start putting in new radiators and turbo props I would just feel the heater hoses coming out of the firewall. If they both get good and hot then the problem doesn't require a new engine.
Ok thanks . You mentioned drain all lubricants and I'm glad you did becuase I'm about to do that also.mine is manual. What lubricants would u recommend for each section.
My actuator seems to be opening and closing becuase you can yell a difference in the restriction of sir flow from the cool side to the hot side. It doesnt not have a ac unit at all by the way. Is there another way to check the actuator. Thanks
Take the hoses off going to the fire wall and see if the water drains out of the find som ay to push low pressure through them, air or water, this would be flushing the heat exchanger, it’s probably plugged and if your luck this will free stuff up, if not year tearing your dash apart to replace it, of you have ac it’s harder
Reverse the hoses. That will cause the water pump to do the backflush. Use clean water.
Use regular dino oil in the axles.
I have the 6 speed. It sounded like I had a handful of gravel in there. Replaced with regular oil (shop did it) and sounded no better. Replaced it with Redline MTL and by the time I got out of my driveway it was a whole new transmission. Smooth shifts. Quiet as a mouse.
Use regular dino oil in the axles.
I have the 6 speed. It sounded like I had a handful of gravel in there. Replaced with regular oil (shop did it) and sounded no better. Replaced it with Redline MTL and by the time I got out of my driveway it was a whole new transmission. Smooth shifts. Quiet as a mouse.
I referenced my 06 owners manual that I downloaded onto my phone. I did transfer, trans, coolant, engine oil. I yet to do diffs. I used atf+4 full synthetic for my trans, and transfer. I used Mopar 5year/100,000mile H.O.A.T antifreeze. Keep in mind its only the concentrate so it will need to be diluted with water to get the 50/50 mix. 1gal will give you 2 gal of antifreeze you can use. Winter i use Castrol edge ep 5w-30 that is preferred for temps 32 and below for the 4.0L. And in summer I use 10w-30. Its whats recommended in the owners manual. I change out my engine oil every 5k miles. Im going to change my trans, transfer and coolant every 30k miles. Don't forget to grease all the grease points. I didn't even know those existed on the tj so I still need to do that as well. I hope this helps you.
Do both of your heater hoses that go into the firewall get hot? If not, you could have a restriction in the heater core. Mine was completely clogged but I was able to clear it with a large syringe by forcing water into it by going back and forth from the inlet to outlet. It finally puked up a long mass of something nasty and started flowing. Then I ran a hose to it and ran it until it was perfectly clear. Although not the best method and I assume no responsibility for anyone's ruptured heater cores, it did work for me and now I have heat for the 2 weeks out of the year that I need it.
The other thing to look at is if there is debris on the outside of the heater core. If you remove the blower motor, you should be able to get access to it. but be careful, the fins are delicate. don't damage them. I have AC so it is first in line but my AC evaporator was covered in leaves and other debris. once I cleaned that off, airflow, cooling and heating improved considerably
The other thing to look at is if there is debris on the outside of the heater core. If you remove the blower motor, you should be able to get access to it. but be careful, the fins are delicate. don't damage them. I have AC so it is first in line but my AC evaporator was covered in leaves and other debris. once I cleaned that off, airflow, cooling and heating improved considerably
I had heat issues for the last few years. My heater core blew, so I replaced it with a performance radiator one. While doing that, I noticed my recirculation Blenddoor actuator was broken, and it was stuck in recirculation. Since the HVAC controls only use recirculation when on AC, my theory is that this could cause the heat not to work. I replaced both, and I have heat again. Since I replaced this while replacing my heater core, I can't confirm which of the two things fixed the issue, but it could have helped. Here is a video where I show how to see if this is broken and how to replace it.
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