cold inside

[ricpope]

my jeep heat has almost stopped blowing. when i turn the temp knob the blend door works fine, had a water pump replaced in the summer, never checked the heat. the radiator is full . any suggestions?
it is a 98

[Mudderoy]

I have one of those photography temp probes in my center vent. I was using back when I was working on the A/C, but I noticed that with the heat on it gets to about 100 degrees after 10 minutes then eventually up to 110.

I need to flush my heater core and see if that improves anything.

[prerunner1982]

You may have a valve under the hood that opens up the coolant to flow through the heater core. If the valve has failed or does not have vacuum hooked up then coolant will not flow to the heater. If you just had work done under the hood there is a good chance it was disconnected.

It's called a Water Valve and had part # 5600 5900

[TheWeiss]

When replacing any parts of the cooling system I've heard that its very important to fully "burp" the system to insure that there are no air bubbles. If there are one could be inconveniently caught somewhere in your heater core and might prevent it from working as well as it could. Depending on who replaced the water pump (if you didn't do it yourself) and how thorough they were this could be your problem.

I've never dealt with a heater core so this could be hearsay so if anyone disagrees or knows this to be wrong please prevent me from leading anyone astray.

[BlueXJ]

Ric if the heater valve is opening and you can feel the water flowing through the hoses to/from heater core then you may have a problem inside the blender door area of the heater. Check for un-hooked vacuum lines under the dash on the passenger side. There is a diaphram that the vacuum needs to activate for heat to come through either the vents or the floor ducts.

[Mudderoy]

I forgot to post this yesterday. I felt the heat a little hotter than normal yesterday so I checked the little temp gauge I have stuck in the center console vents. About 129 degrees!!! I had the fan on the lowest setting.

So I'm still not sure what the temp should be but the 129 felt good. I had to turn it down after a little while. I think it was around 50 yesterday, so I'm not sure if that 130 would put a dent in the 20's we are supposed to see Saturday/Sunday.

Hey I found this...

http://xjtalk.com/images/special/2000xjmaxheater.jpg

[Mudderoy]

http://www.teamgrandwagoneer.com/partsSQL/images/1612-hvalve.jpg

:link: (http://www.teamcherokee.com/Cooling/index.html)

[4.3LXJ]

So I'm still not sure what the temp should be but the 129 felt good. I had to turn it down after a little while. I think it was around 50 yesterday, so I'm not sure if that 130 would put a dent in the 20's we are supposed to see Saturday/Sunday.


If the heat is not keeping up in the cold weather, there is a trick you can do to increase your heater efficiency. Disable the AC compressor by pulling the relay in the relay box or in 84-86 unplug the low pressure safety switch. It is on the filter drier. Here is a pic of the 4.0L set up on the passenger frame rail.

http://i649.photobucket.com/albums/uu215/warriorsuspension/IMG_0162.jpg

This disables the compressor and allows you to run heat in the MAX AC position. This opens up a little door on the heater assembly that recirculates the air inside the cabin. You will then be reheating your inside air instead of trying to heat cold outside air. With a struggling heater, it makes quite a difference. The only draw back is that the windows fog after awhile and you have to go back to regular heat to change the air out.

[BlueXJ]

Clean out those pine needles as they have acid in them and are also hydoscopic. Very bad mojo for your XJ.

[ricpope]

today i fixed the heat. it was simple. replace the radiator cap.
i was goin to flush the heater core and then i looked at the cap .

[TheWeiss]

What did it look like?

[4.3LXJ]

Clean out those pine needles as they have acid in them and are also hydoscopic. Very bad mojo for your XJ.

Cleaned out. Took this pic a while back when I started work on it again. I had the hood off and did not realize how many needles our pine tree got rid of.