BLHTAZ Posted January 29, 2008 Share Posted January 29, 2008 The heater core in my MJ was bad when I bought the truck a year ago, but I have never addressed it as there have been too many other things of more importance than that. Heat is not a priority in FL...unlike AC. ;) My question is...can the core be changed without opening the AC system or does the evaporator have to be disconnected to remove the heater core? Anyone have a write up on this or any good advice as it looks like a real PITA to do? Link to comment Share on other sites More sharing options...
armybmbsqd Posted February 1, 2008 Share Posted February 1, 2008 I've been wondering the same thing. I have a Chiltons and a Haynes and one says to empty the AC system and the other says nothing about it. Any practical experience would be great. I was also wondering if you could clean out a heater core with something like CLR? Unhook the lines, plug one and pour the CLR in and let it soak for a bit then flush it out. My truck heats up OK but the heater just doesn't seem to get warm enough. I put in a new thermostat a month ago but it didn't help much. Pat K 89 MJ 4.7 Stroker Link to comment Share on other sites More sharing options...
swilson Posted February 1, 2008 Share Posted February 1, 2008 I've been wondering the same thing. I have a Chiltons and a Haynes and one says to empty the AC system and the other says nothing about it. Any practical experience would be great.I was also wondering if you could clean out a heater core with something like CLR? Unhook the lines, plug one and pour the CLR in and let it soak for a bit then flush it out. My truck heats up OK but the heater just doesn't seem to get warm enough. I put in a new thermostat a month ago but it didn't help much. Pat K 89 MJ 4.7 Stroker Every winter my truck does the same thing. Pull both lines off going to the heater core. Take your garden hose and turn it on full. Put the water in the top pipe and let it flow for a minute then switch to the bottom pipe and let flow for a minute. Do this a few times and you should be good to go. It works for me every time and only takes 20 minutes. One thing that I do to save me from dumping all my antifreeze from bottle an head is pinch the two hoses with needle nose vice grips or hose pinch if you have them. This save the head ache of burping the system. Give it a try!! Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 1, 2008 Share Posted February 1, 2008 I've been wondering the same thing. I have a Chiltons and a Haynes and one says to empty the AC system and the other says nothing about it. Any practical experience would be great.I was also wondering if you could clean out a heater core with something like CLR? Unhook the lines, plug one and pour the CLR in and let it soak for a bit then flush it out. My truck heats up OK but the heater just doesn't seem to get warm enough. I put in a new thermostat a month ago but it didn't help much. Pat K 89 MJ 4.7 Stroker I read a writeup on NAXJA where someone used Drano to clean the heater core, said it worked fine. You may also have have a problem with the water control valve not opening. I just eliminated it by swapping in 97+ heater hoses, since the 97+ XJs don't have a water control valve. Heat works much better now too. Weren't you at Redstone previously? Link to comment Share on other sites More sharing options...
LEAD_NOT_FOLLOW Posted February 1, 2008 Share Posted February 1, 2008 http://www.greatlakesxj.com/tech/heatercore.html Total PITA! FSM says something like 8 hours. Some have said they got away with not removing the dash, others swear you have to. I've not had heat the last 3 years in my XJ and I've done the hose trick about 50 times with no luck. I've just decided to deal with it instead of doing it... Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 1, 2008 Share Posted February 1, 2008 http://www.greatlakesxj.com/tech/heatercore.html Total PITA! FSM says something like 8 hours. Some have said they got away with not removing the dash, others swear you have to. I've not had heat the last 3 years in my XJ and I've done the hose trick about 50 times with no luck. I've just decided to deal with it instead of doing it... Yeah, I've read the same things. Seen plenty of writeups changing the heater core w/o A/C, but not with. My FSM says pull the dash - ARGH. Luckily I haven't had to do it. :D But it must be tough dealing with it in your neck of the woods........ :oops: Link to comment Share on other sites More sharing options...
Oizarod115 Posted February 1, 2008 Share Posted February 1, 2008 it IS a total pain in the @$$... i watched my boss tear down an entire dash of a new style XJ (exploded into a million plastic pieces everywhere) took him a few hours, (he's a total badass) but it looked like sucky work man. Link to comment Share on other sites More sharing options...
LEAD_NOT_FOLLOW Posted February 1, 2008 Share Posted February 1, 2008 http://www.greatlakesxj.com/tech/heatercore.html Total PITA! FSM says something like 8 hours. Some have said they got away with not removing the dash, others swear you have to. I've not had heat the last 3 years in my XJ and I've done the hose trick about 50 times with no luck. I've just decided to deal with it instead of doing it... Yeah, I've read the same things. Seen plenty of writeups changing the heater core w/o A/C, but not with. My FSM says pull the dash - ARGH. Luckily I haven't had to do it. :D But it must be tough dealing with it in your neck of the woods........ :oops: Yeah it sucks, I don't drive the XJ a ton, but when I do I bundle up.... I'd of changed it a long time ago if I didn't have so much electronics's attached to my dash/under dash that I'd have to pull as well. TOTAL PITA! Link to comment Share on other sites More sharing options...
armybmbsqd Posted February 1, 2008 Share Posted February 1, 2008 I read a writeup on NAXJA where someone used Drano to clean the heater core, said it worked fine. You may also have have a problem with the water control valve not opening. I just eliminated it by swapping in 97+ heater hoses, since the 97+ XJs don't have a water control valve. Heat works much better now too. Weren't you at Redstone previously? Yes, I was at Redstone. I retired from the Army in October and moved back up north to the land of %$@$%@ cold winters!!! I am going to school full time, working full time at O'Reilly Auto Parts and letting my hair grow Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 1, 2008 Share Posted February 1, 2008 Yes, I was at Redstone. I retired from the Army in October and moved back up north to the land of %$@$%@ cold winters!!!I am going to school full time, working full time at O'Reilly Auto Parts and letting my hair grow Cool! Or should I say Cold. :eek: I stayed in the AO; not too bad here......... Link to comment Share on other sites More sharing options...
BLHTAZ Posted February 1, 2008 Author Share Posted February 1, 2008 I guess one of these days I will just have to start investigating it myself. Mine is roken and leaking on the floor, so I have no choice but to either live without it or fix it. Like I said...it's not a big deal here in FL, but it just irritates me when thinks are not working as they should. Link to comment Share on other sites More sharing options...
TNT Posted February 2, 2008 Share Posted February 2, 2008 If you have had the dash out once, its easier the second time. When Pat and I tore the dash out of my '95 it took under an hour. I could do it again by myself in about 45 mins. Using a cordless drill to remove screws and small bolts saves a bunch of time. A 1/4 air ratchet helps too. You really only need to disconnect the passenger side and some of the drivers side. The just swing the dash onto the passenger seat leaving it pivot on the drivers side. Just lower the column pull the console and go to town on the dash. The heater box can be removed after swinging the dash out of the way. Discharge the AC disconnect the hoses and unbolt the box. Use the cordless drill to disassemble the heater/ac box and swap ot the core. I'm sure I could do it in 3-4 hours. With practice 2-3 hours is about right. I can replace an evaporator in a ZJ in 2 hours and LH Chrysler cars in an hour and a half. I just swing the dash on those vehicles also. I'm an ex-mopar tech so believe me it can be done. If you do it with hand tools and pull the dash it's about a 6 hour job tops. Link to comment Share on other sites More sharing options...
ifixit8 Posted February 2, 2008 Share Posted February 2, 2008 If you have had the dash out once, its easier the second time. When Pat and I tore the dash out of my '95 it took under an hour. I could do it again by myself in about 45 mins. Using a cordless drill to remove screws and small bolts saves a bunch of time. A 1/4 air ratchet helps too. You really only need to disconnect the passenger side and some of the drivers side. The just swing the dash onto the passenger seat leaving it pivot on the drivers side. Just lower the column pull the console and go to town on the dash. The heater box can be removed after swinging the dash out of the way. Discharge the AC disconnect the hoses and unbolt the box. Use the cordless drill to disassemble the heater/ac box and swap ot the core. I'm sure I could do it in 3-4 hours. With practice 2-3 hours is about right. I can replace an evaporator in a ZJ in 2 hours and LH Chrysler cars in an hour and a half. I just swing the dash on those vehicles also. I'm an ex-mopar tech so believe me it can be done. If you do it with hand tools and pull the dash it's about a 6 hour job tops. what do you do when the bolts for the heater box are rusted all the way thru, and the speed clips just spin? the only thing that I can think of doing is either cutting the bolts with a dremel or just breaking the heater box housing. thanks in advance. because i will more than likely do this in a few months, because i still have the mouse nest smell lingering. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted February 2, 2008 Share Posted February 2, 2008 http://www.naxja.org/forum/showthread.php?t=931690 that's via naxja. you will NOT have to discharge the a/c system, but you will probably have a hell of a time doing it without discharging it. just take your time, and think....it won't be easy, but you can swing the condensor around out of the way. as for the bolts spinning...are you talking about the ones through the firewall? they'll unthread from the heater box...just be sure to remove them from the firewall then thread them back into the heater box so that you can get it lined up when you reinstall it. and yeah, TNT and I took about 45 minutes...and we stood there BS-ing for all of 20 of those minutes (we BOTH talk alot :roll: which makes it hard to get things done sometimes, but we still get things done in half the time it normally takes.... Link to comment Share on other sites More sharing options...
ifixit8 Posted February 4, 2008 Share Posted February 4, 2008 as for the bolts spinning...are you talking about the ones through the firewall? they'll unthread from the heater box...just be sure to remove them from the firewall then thread them back into the heater box so that you can get it lined up when you reinstall it. and yeah, TNT and I took about 45 minutes...and we stood there BS-ing for all of 20 of those minutes (we BOTH talk alot :roll: which makes it hard to get things done sometimes, but we still get things done in half the time it normally takes.... yeah i was refering to the bolts that go thru the firewall. when my friend and I tried to take out the box and core the bolts had just spun. Link to comment Share on other sites More sharing options...
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