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no heat

Me007gold

NAXJA Forum User
Location
San Antonio, TX
its starting to get "cold" and ive disovered that my heat is not working. It is not overheating at all, the temp is running a little but under 210. the blower motor is working, cuz it is blowing a lot of cold air out. also some times when i move the knob to tell it where to place the air, there is a delay. Do i have a vacume leak somewhere? and if so how do i find it? i also flused my radiator yesterday and that didnt help either
 
Are you sure the water level is full? Also, I would pull hoses off the heater core and flush it seperately when I do a radiator flush. A delay with the air could mean a small vacuum leak, but mine does that too and I have no issues with heat. Run the jeep for about 10 minutes and feel the heater hoses, one should be fairly warm and the other should be a little cooler with the heater on.
 
Okay....check the hoses...one hot, one luke warm.

If they are both cold you have no heat going through the core. If one is warm, but the other is cold, then the core is probably plugged. If both are warm and close in temp to each other, then the problem is the in dash control doors. That very well could be vacuum related. Also..park under a tree maybe? Leafs can clog and block door movement if the screen is torn or missing on the cowl air intake area.
 
flush the rad. core seperately and check for vacuum leaks.

when I say flush seperately, I mean disconnect the input AND output hoses as well as the vacuum switch that's between the hoses and the heater core, then use a garden hose and flush top to bottom, then bottom to top, and top to bottom again. repeat until the gunk is out...it should mostly come out with the bottom to top.
 
yes, it is possible that that switch went bad.

you don't actually need it, you can eliminate it. if you eliminate it, then plug the vacuum line that leads to it. I did this on my xj and haven't regretted it.
 
jeepcomj said:
yes, it is possible that that switch went bad.

you don't actually need it, you can eliminate it. if you eliminate it, then plug the vacuum line that leads to it. I did this on my xj and haven't regretted it.

if i were to eliminate it, how would i go about doing it?
 
Sounds like your Heater control valve has gone bad if both heater hoses are hot. It is a valve that is inline in one of your heater hoses. Normally pretty cheap too.
 
tow2topgun said:
Sounds like your Heater control valve has gone bad if both heater hoses are hot. It is a valve that is inline in one of your heater hoses. Normally pretty cheap too.

according to autozone and advance auto online my jeep dosnt have a heater control valve.
 
its a 98

untitled-2.jpg
 
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If the above suggestions fail (they are cheaper and easier than the next step). Look at the heater core. easiest thing here is the thermostat, fluid, flush sometimes, but if the first two don't add up to anything, I am thinking heater core, which still isn't bad to replace. Need the core, gasket and sealant. Still hope this isn't the case for you.
 
The temp issue tells me that the core isn't picking up any heat though since you're engine is getting hot.
 
Me007gold said:
if i were to eliminate it, how would i go about doing it?
here is what it looks like (generally). it's in the rear right of your engine bay, going into your firewall. it has 1 vacuum line going into it.
valve.gif


to bypass you simply put remove it, plug the vacuum hose, put the "from water pump" hose into the top connector, and the "from thermostat" hose to the lower connector
 
jeepcomj said:
here is what it looks like (generally). it's in the rear right of your engine bay, going into your firewall. it has 1 vacuum line going into it.
valve.gif


to bypass you simply put remove it, plug the vacuum hose, put the "from water pump" hose into the top connector, and the "from thermostat" hose to the lower connector


I have a 92 XJ with no heat either, Tried rad flush and core flush seperatly. I replaced the thermostat, but still have no heat. My core hoses are one super hot, and one luke warm. I noticed that i have very little vacuum, to this control valve. I follow the vacuum line back and it goes into the firewall just about the heatercore hoses and i feel alot of air coming from there. Is this my problem? Would doing the above bypass solve my problem, or is there a way to fix the vacuum issue? Thanks

PS sorry if im hijacking.
 
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