djdr1988 Posted December 20, 2013 Share Posted December 20, 2013 I have searched the threads and haven't found an exact issue, but I have an 89 Comanche and the heater will lightly blow luke warm air from the dash and defrost, but it constantly blows ice cold air at the floor. I have tried flushing it and replaced the coolant valve for the heater core. I have also checked the blend door for function and that seems to be working as well. Also, when I change the blower location it does change. Any advice guys? Link to comment Share on other sites More sharing options...
TheDirtyJeep401 Posted December 20, 2013 Share Posted December 20, 2013 Have you checked your thermostat? Could be stuck open Link to comment Share on other sites More sharing options...
gogmorgo Posted December 20, 2013 Share Posted December 20, 2013 There's also a vacuum operated valve that shuts off coolant flow to the heater core when the heat's off. It's not uncommon for those to quit working properly. Link to comment Share on other sites More sharing options...
carnuck Posted December 20, 2013 Share Posted December 20, 2013 The valve being replaced won't help if the hose to it isn't getting vacuum. As long as the temp goes up on the gauge, you can apply vacuum directly to the valve to get heat happening. If the vacuum ball (in the stupidest place, behind the right front bumper corner) is cracked, some things may work and others won't. Link to comment Share on other sites More sharing options...
cruiser54 Posted December 20, 2013 Share Posted December 20, 2013 First off, eliminate that worthless and failure prone valve. Just use a connector where it used to be. Plug the vacuum line. What kind of temps is your engine running at? Link to comment Share on other sites More sharing options...
djdr1988 Posted February 7, 2014 Author Share Posted February 7, 2014 Sorry I haven't posted on this in a while. My temps run normal just below 210 on the gauge. The thermostat is brand new. I haven't checked the vacuum ball in the fender yet. I will do that this weekend. The day after I posted this, the heater was working properly. However, it has started to be intermittent again. Only working when it wants to. I have got the parts to remove the vacuum valve for the heater core, also doing that this weekend. I have also notice the old freeze plug block heater is leaking. I am going to replace that as well, I figure it's letting air in the system. This is the renix setup. I have all the stuff to change to a non sealed system, just haven't had the time to do it. Any other advice would be greatly appreciated. Link to comment Share on other sites More sharing options...
cruiser54 Posted February 7, 2014 Share Posted February 7, 2014 Replace the freeze plug. Get a 703-1396 cap from Napa for the bottle. Removing the heater control valve as you already planned is a good idea. I always relocate the vac balls ro the bottom of the coolant bottle bracket, eliminating all the troublesome vac hoses to the bumper. Link to comment Share on other sites More sharing options...
djdr1988 Posted February 7, 2014 Author Share Posted February 7, 2014 Thanks for the advice. Just curious, what does that cap do that the stock cap doesnt? Link to comment Share on other sites More sharing options...
cruiser54 Posted February 7, 2014 Share Posted February 7, 2014 Thanks for the advice. Just curious, what does that cap do that the stock cap doesnt? Seals properly. And lasts longer than the chinese junk replacement caps that are generally available. Link to comment Share on other sites More sharing options...
djdr1988 Posted February 7, 2014 Author Share Posted February 7, 2014 Got ya. Thanks for all the help and advice guys. I will update as I get parts replaced and see what happens. Link to comment Share on other sites More sharing options...
djdr1988 Posted February 11, 2014 Author Share Posted February 11, 2014 I replaced the parts and now the coolant flows very strong into the bottle, but the heater is only blowing Luke warm at best. Any other ideas? I have flushed the core and it flowed strong. Link to comment Share on other sites More sharing options...
cruiser54 Posted February 11, 2014 Share Posted February 11, 2014 Compare the temp of the upper radiator hose with the temp of each heater hose where it goes through the firewall. Your hand is perfectly fine to do this. Link to comment Share on other sites More sharing options...
djdr1988 Posted February 11, 2014 Author Share Posted February 11, 2014 Ok I should also add that right after I changed the parts the heater worked great. Now it's back to this Link to comment Share on other sites More sharing options...
cruiser54 Posted February 11, 2014 Share Posted February 11, 2014 How's your coolant level in the bottle? Still need to check those hoses with your hand. That will help us narrow this down. Link to comment Share on other sites More sharing options...
1989 Eliminator Posted February 11, 2014 Share Posted February 11, 2014 So I had a similar issue where when the tmep outside was below -10 deg. F only cold air would be blowing out and when it did work it was luke warm. So it sounds like you flushed the heater core. But maybe a different way. They way I flushed mine was take the upper heater hosesoff from the thermostat housing and the lower heater hose off from that heater control valve. I then put a peice of rubber inbetween a vise grip to crimp the hose going to the bottle. I did this becasue when I blew into one of the heater hoses with my air compressor I wanted all the pressure to go to the heater core not into the bottle. I then poured water down both hoses and blew into each of the hoses. I did this process a few times back and forth until I thought it was sufficent. I also put a empty coolent jug at the end of the opposite hose I was blowing into so all the water and crud wouldnt go all over my engine compartment. After this my truck was putting out heat like nothing else. Big difference. I will say though, even thought my heat was awesome when it worked, during these extreme cold days here in michigan my vents would blow cold air. Not sure if it was the blend door or the heater control valve. Just giving my input and trying to help. :dunno: Link to comment Share on other sites More sharing options...
yxmj Posted February 11, 2014 Share Posted February 11, 2014 Ok I should also add that right after I changed the parts the heater worked great. Now it's back to this Take a minute and read my flush instructions in this thread (second post down). http://comancheclub.com/topic/41758-no-heat-in-89-40-mj/ I had the same thing flushed the core strong flow......no heat.....I read on an XJ site that jeep cores can flow well even if the small passages that will emit most of the heat are clogged solid. After I did the flush i described above with the CLR an then the vinigar it was like night and day :thumbsup: (as long as you are positive you have a good operational thermostat) Link to comment Share on other sites More sharing options...
djdr1988 Posted February 11, 2014 Author Share Posted February 11, 2014 I will give that a try and see if it helps. Thanks again for all the advice. Link to comment Share on other sites More sharing options...
Burntoast914 Posted February 12, 2014 Share Posted February 12, 2014 I also have the same issue it warms up for 30 mins then alittle heat comes out. But with mines if I drive it warms up nicely like warm warm but if I change to bi-level or vents it goes cold or even stopping at a red light. But weird thing was I had it ok four Bout a hour n hear level was fine. But of course it stopped working Link to comment Share on other sites More sharing options...
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