TajMan Posted December 8, 2007 Share Posted December 8, 2007 Well after I replaced my blower motor and fixed my vents so air blew, I learned the HEAT never comes! No matter how long engine warms up, how long you leave blower on hi on heat setting, it never warms out the vents. Thermostat was new so thats not the issue, coolant does get hot. It makes me angry my 87 doesn't have a temp gauge just a dummy light. (had an 88 short while, it had temp-oil press-and battery gauges instead of the dummy lights) I'm pretty sure heater core isn't "bypassed".... my problem? Link to comment Share on other sites More sharing options...
Eagle Posted December 8, 2007 Share Posted December 8, 2007 The heater core is probably blocked. Link to comment Share on other sites More sharing options...
HOrnbrod Posted December 8, 2007 Share Posted December 8, 2007 The heater core is probably blocked. Either that or the water control valve is stuck. Disconnect the two heater core hoses at the firewall (red circle) and flush the core with a garden hose both ways until all the crap comes out. Since the 1997+ XJs have no water control valve, I just picked up a set of the newer XJ heater hoses and bypassed the water control valve (where the yellow circle is). One less thing to go bad, and the heat works better than before. And plug the vacuum line going to the water control valve if you do this. Link to comment Share on other sites More sharing options...
carnuck Posted December 9, 2007 Share Posted December 9, 2007 Be careful not to get much pressure into the heater core! Otherwise it will expand like an accordion and burst at the seams! Link to comment Share on other sites More sharing options...
TajMan Posted December 9, 2007 Author Share Posted December 9, 2007 I'll start with a garden hose and see if water passes through it. Link to comment Share on other sites More sharing options...
tjbliley Posted December 9, 2007 Share Posted December 9, 2007 You could also try manually moving the control valve to see if it is bad. Link to comment Share on other sites More sharing options...
McClare Posted December 9, 2007 Share Posted December 9, 2007 would bypassing that valve mess with your A/C at all? Link to comment Share on other sites More sharing options...
JeepcoMJ Posted December 9, 2007 Share Posted December 9, 2007 would bypassing that valve mess with your A/C at all? not really. it could possibly be a bit warmer but not likely Link to comment Share on other sites More sharing options...
HOrnbrod Posted December 9, 2007 Share Posted December 9, 2007 would bypassing that valve mess with your A/C at all? not really. it could possibly be a bit warmer but not likely No warmer at all as long as the flapper door is functioning. Plus it keeps coolant circulating through the heater core so it not as likely to clog up. Mopar got rid of the H2O control valve entirely in the 1997+ models, and made no physical hardware changes to the heating/AC system. Link to comment Share on other sites More sharing options...
carnuck Posted December 10, 2007 Share Posted December 10, 2007 If you have a dent in the right side of the front bumper the vacuum ball may be crushed, which means the controls won't do as they are told either! Link to comment Share on other sites More sharing options...
HOrnbrod Posted December 10, 2007 Share Posted December 10, 2007 If you have a dent in the right side of the front bumper the vacuum ball may be crushed, which means the controls won't do as they are told either! If the vacuum ball is crushed, which should be fairly easy to see, you'll have more problems than just the climate control problems. Link to comment Share on other sites More sharing options...
carnuck Posted December 11, 2007 Share Posted December 11, 2007 They crack real easy. Link to comment Share on other sites More sharing options...
TajMan Posted December 13, 2007 Author Share Posted December 13, 2007 If you have a dent in the right side of the front bumper the vacuum ball may be crushed, which means the controls won't do as they are told either! I have a dent near the mount on the driver's side of front bumper, right side if you're LOOKING at the front end of truck. ??? Link to comment Share on other sites More sharing options...
chicofuentes0224 Posted December 13, 2007 Share Posted December 13, 2007 If you're looking at the front end mine is on the left side. Link to comment Share on other sites More sharing options...
carnuck Posted December 15, 2007 Share Posted December 15, 2007 passenger's side Link to comment Share on other sites More sharing options...
Mobius1 Posted December 16, 2007 Share Posted December 16, 2007 So if I have read all this correctly, if the bumper is hit on the right side (passenger side) enough to dent it good then that vac ball could be toast thus making the heat not really work? My 88 2.5 MJ has luke warm heat on bylevel but when I put it on "Heat" it comes out cold? So whats up with that? Also with that picture of the engone bay is it possibe for someone to post one of the 2.5L bay without a/c because mine looks nothing like that...not even close. I'm only concerned about having realy heat because my wife will be driving it for the most part while i'm gone for basic training and would like to get that fixed on my own if possible along with other things. Link to comment Share on other sites More sharing options...
CWLONGSHOT Posted December 16, 2007 Share Posted December 16, 2007 You don't need a pic, its easy to find what the guys are speaking of. there are two lines running into the firewall in that general vicinity. one going in to the heater-core, the other is the return side going back in to the engine. The vac ball is kinda like a vacuum reserve allowing the doors to open so the airflow allows heat or cold from out side air to mix. Easy to see and find its right behind the bumper on the pass side in the front. there are two different canisters, one is a ball the other is a oval. It depends on the options of your rig when new as to which you have. Any way just remove (two screws) and check hoses and cracks. Nothing fancy, remove a hose and blow or suck and see if there is any leaks. Here is a pic of the placement of my vac ball. Look in the upper left corner of the pic: Its most likely the heater core is bad/plugged. You can try a flush but I would just replace. Not awful expensive or hard (as long as no A/C) and your done. CW Link to comment Share on other sites More sharing options...
TajMan Posted December 17, 2007 Author Share Posted December 17, 2007 How hard to change heater core if I have AC? Thinking about just removing AC anyway, I'm sure it doesn't work right now. Link to comment Share on other sites More sharing options...
CWLONGSHOT Posted December 17, 2007 Share Posted December 17, 2007 Some vehicles are REALLY hard to do if you have AC. I haven't done this to a MJ with AC. Its pretty easy on one with out it... I don't imagine its a awful job. CW Link to comment Share on other sites More sharing options...
JeepcoMJ Posted December 17, 2007 Share Posted December 17, 2007 Some vehicles are REALLY hard to do if you have AC. I haven't done this to a MJ with AC. Its pretty easy on one with out it... I don't imagine its a awful job. CW it won't be fun, but it can be done without yanking the dash. I'd rather yank the dash to do it though personally...then you have all the space in the world. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted December 17, 2007 Share Posted December 17, 2007 http://www.naxja.org/forum/showthread.php?t=931690 there's a link to doing it, i think without a/c Link to comment Share on other sites More sharing options...
TajMan Posted December 29, 2007 Author Share Posted December 29, 2007 I believe my heater core is blocked I have 2 new hoses connected there on firewall, using a garden hose trying to force water through one- I can try to force a good little amount of pressure and it just builds never coming out the other tube. What can be done to try and clean? I have some Drano here I was thinking of putting in and letting sit, try to flush with water again after. I figure I can't do much to ruin anything if I end up just having to replace heater core anyway. Link to comment Share on other sites More sharing options...
TajMan Posted December 30, 2007 Author Share Posted December 30, 2007 Drano did it, then forcing with garden hose finally flushed my heater core! :) Everything re-assembled, Just new pieces of Autozone 3/4" heater hose used, that one vacuum-actuated valve removed. New coolant bottle radiator cap I needed too. Heat works, kind of mellow but it works- huge difference from nothing when its been frigid out. Thanks for tips guys 1 more problem thread eliminated. Link to comment Share on other sites More sharing options...
TajMan Posted January 2, 2008 Author Share Posted January 2, 2008 THUMBS UP And I saw that the vacuum hose was disconnected on my MAP sensor and THAT is what had been making the thing run crappy and worry me the past short while. I got some Seafoam, you guys like Seafoam? Link to comment Share on other sites More sharing options...
jtdesigns Posted January 2, 2008 Share Posted January 2, 2008 THUMBS UPAnd I saw that the vacuum hose was disconnected on my MAP sensor and THAT is what had been making the thing run crappy and worry me the past short while. I got some Seafoam, you guys like Seafoam? Seafoam isn't recommended on engines over 150k. I used it before on my Rodeo, I guess it helped quieten down the lifters for a week or so, but it did make a cool smoke screen after I treated with it!! Link to comment Share on other sites More sharing options...
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