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Only Blows Cold...

OCMI_Teddy

OCMI_Teddy

NAXJA Forum User
Location
San Diego
Being winter I'd like to get some heat. My 96 xj is only blowing out cold air, even when the engine temp gets up to the 200 range. It blows cold on the defrost, heater and vent settings. I've hear of heating core issues. Is this one of them?
 
could be a clogged heater core. are the 2 lines(in/out) of the heater core getting hot?
 
Last edited:
Check the serp. belt tension. Easier place to start than heater core. Get a Krikit-II from NAPA, the belt needs to be tighter than you can gauge by hand (170# old belt, 190# new belt iirc). $15 and you won't (shouldn't) make a mess, plus you get a new tool.
 
After you check your core, check the blend door as well. You should feel it moving as you slide the temp selector back and forth. It's cable operated and sometimes the cable end comes off the selector or the door.
 
Some good responses here....

Heater control valve, blend door, heater core are all possibilities. As 89xj mentions, first thing to check is the temp of both heater hoses on the heater core.
 
Where are these hoses? I read that the heater core is behind the dash board so should i be looking for two hoses that run from the firewall to the radiator?
 
OCMI_Teddy said:
Where are these hoses? I read that the heater core is behind the dash board so should i be looking for two hoses that run from the firewall to the radiator?
Click to expand...

yes, on my 89 the heater core hoses go into the heater core through the passenger side firewall. they are really easy to see.
 
two black hoses will run alongside the passenger side of the valve cover. One will go directly to the thermostat while the lower one will connect up to a metal curved pipe that will lead to the thermostat. Follow these back to the passenger side firewall and you will then have located your heater core inlet and outlet.
 
I think the heater core is cloged. The bottom "in" hose is hot and the top "out" is cold.

I've read that you had to flush the radiator system, or take out the dash board. What's that best way of doing this?
 
OCMI_Teddy said:
I think the heater core is cloged. The bottom "in" hose is hot and the top "out" is cold.

I've read that you had to flush the radiator system, or take out the dash board. What's that best way of doing this?
Click to expand...


just flush the heater core. leave the hoses on the core and disconnect at a connection in the engine bay. leaving the hoses on the core itself allow you to direct the flow of water. use a garden hose on the line that was cold and back flush the core.

its an easy job. no removal of the dash. just disconnect 2 hoses, turn on water from garden hose and watch nasty stuff come out the other hose.
 
I agree on the heater core flush. My 89 had the exact same issues as yours, I flushed my heater core and now my heat is as hot as can be.
 
this is a very helpful thread. My 2000 xj is randomly blowing cold when on hot. it has been about 5 Degrees Fahrenheit for the high around here lately. do i need to flush the heater core?
 
Combat Cow. I have a 2000, this seems to be a fairly common issue. First id make sure you have enough coolant in your radiator. If not, add more coolant. Keep checking the radiator level every so often. If it keeps taking more and more fluid, you might have a leak in a line, or possibly a bad head gasket.
I ran my Chero with very little coolant for a while. They dont really overheat to easily, so it was hard to notice. Esp in the winter.

I would def try that befor flushing your core.
 
combatcow said:
this is a very helpful thread. My 2000 xj is randomly blowing cold when on hot. it has been about 5 Degrees Fahrenheit for the high around here lately. do i need to flush the heater core?
Click to expand...



the random cold air may be your blend door flopping around. i believe the 2000 has an electric motor actuated blend door, not entirely sure though. if not motor actuated then could be cable actuated. had this prob on my 98 and reconnected cable to blend door and had heat again.
 
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