Kenny_McCormic wrote: if both hoses are hot with the blower cranked, I'd guess you have some blend door issue somewhere and it's not getting full airflow over the core.
I just replaced the blend door yesterday morning because i DID have a blend door issue. I no longer have a blend door issue.
MrChaos wrote: IS the radiator clear and the coolant in good shape? Has the coolant system been flushed recently?
5) New radiator
Coolant looks great and fresh because it IS fresh. 
rcutclif wrote:Kenny_McCormic wrote: if both hoses are hot with the blower cranked, I'd guess you have some blend door issue somewhere and it's not getting full airflow over the core.Or your ducting is broken (or gone or not seated correctly) and air is flowing around the core rather than through it.
I suppose this is possible, but wouldn't that also affect actual air movement out the vents?
mad_machine wrote:Swank Force One wrote:Have you tried it in this configuration?bigdaddylee82 wrote: Fresh air door stuck open? Having to warm cold air from outside instead of recirculating?The only time a late XJ recirculates is when "Max A/C" is selected. It pulls from outside air at all other times.
Are you asking if my heat is hot when my a/c is on at the same time fighting it?
Well, no... it's not real hot.
How is the air flow coming out of the vents? Is it weaker than your other XJ?
PseudoSport wrote: How is the air flow coming out of the vents? Is it weaker than your other XJ?
Maybe slightly, but it's at least 80% the flow. There's so many differences in the HVAC between the two that i haven't really been giving that second thought. Haven't had the chance to compare to another 00-01.
In reply to Swank Force One:
does the A/C side of the system work?
Swank Force One wrote:rcutclif wrote:I suppose this is possible, but wouldn't that also affect actual air movement out the vents?Kenny_McCormic wrote: if both hoses are hot with the blower cranked, I'd guess you have some blend door issue somewhere and it's not getting full airflow over the core.Or your ducting is broken (or gone or not seated correctly) and air is flowing around the core rather than through it.
Likely I would guess, unless the air can somehow flow all the way around the core but stay inside the vents. For example if there is supposed to be foam tape around the core to seal it to the inside of the duct and that tape isn't there, I could see good airflow from the vents, but the air not being heated much.
Swank Force One wrote:Kenny_McCormic wrote: if both hoses are hot with the blower cranked, I'd guess you have some blend door issue somewhere and it's not getting full airflow over the core.I just replaced the blend door yesterday morning because i DID have a blend door issue. I no longer have a blend door issue.
Well yeah, I get that. However, if you're pumping hot coolant through the core and that heat isn't being exchanged into the air flowing though the heater box/core, then air must not be flowing through the heater box/core.
MrChaos wrote: In reply to Swank Force One: does the A/C side of the system work?
Not well. Has a leak. When it's charged it worked as well as expected for a system with a blend door stuck in the middle.
I'm confident if I fixed the leak now that the blend door works that it would work fine.
I really hope I won't have to pull the dash just to see if air is going where it should...
...i'll cry.
Swank Force One wrote:mad_machine wrote:Are you asking if my heat is hot when my a/c is on at the same time fighting it? Well, no... it's not real hot.Swank Force One wrote:Have you tried it in this configuration?bigdaddylee82 wrote: Fresh air door stuck open? Having to warm cold air from outside instead of recirculating?The only time a late XJ recirculates is when "Max A/C" is selected. It pulls from outside air at all other times.
most cars also engage the air con when you set the heat to defrost.. wether on full heat or on full cold.. and usually they will still put out full heat when on that setting.
The only thing I can think of.. is something my old Fiat Spiders had. The valve was not only cable activated, but had something of a thermostat as well. If it got to hot, it was supposed to start cutting back the water flow to cool the core down.. I imagine to keep it from melting anything near by.
So what I am thinking, this problem has to be something to do with the little valve that allows hot water into the core
In reply to mad_machine:
This is an old american car(in design at least), the water pump bypass circuit is the heater core, there is no coolant flow control, its all done with airflow.
Yep. All flow through the core, all the time.
Make sure the heater core fins are clean. You can also try reducing coolant flow, too fast of a flow can cause less heat transfer.
Are you sure the HVAC panel is working properly?
Did you actually take the core out? Could there be a possibility there is something in the core box blocking the air flow?
SyntheticBlinkerFluid wrote: Are you sure the HVAC panel is working properly? Did you actually take the core out? Could there be a possibility there is something in the core box blocking the air flow?
Yes the panel is working correctly. All fan speeds work, vent location works, and the blend door motor is moving.
The core has been in the truck since we bought it. Was replaced 3 months before we bought it. Heat has been E36 M3ty the whole time.
So... it's not new, per se, but flows well, no gunk comes out, and I seriously doubt the core itself is the culprit.
I will get an IR temp reader on the hoses though.
It being a ducting issue is possible, but like I said, i'll cry.
Swank Force One wrote: The core has been in the truck since we bought it. Was replaced 3 months before we bought it. Heat has been E36 M3ty the whole time.
massive red flags from this statement.
have you physically pulled the heater core and leak/pressure tested it?
also I see a lot of mentions on the Jeep forums about reverse flushing the heater core fixing issues.
Also a lot of air in the coolant lines causing issues like this.
and people also just cutting a hole in the glove box/bottom of the dash for easier access since the 96-06 XJ's had heatercore/bleand door issues.
Swank Force One wrote:SyntheticBlinkerFluid wrote: Are you sure the HVAC panel is working properly? Did you actually take the core out? Could there be a possibility there is something in the core box blocking the air flow?The core has been in the truck since we bought it. Was replaced 3 months before we bought it. Heat has been E36 M3ty the whole time.
I think you just answered your own question. I almost guarantee there is something inside the heater box with the core blocking the air flow.
SyntheticBlinkerFluid wrote:Swank Force One wrote:I think you just answered your own question. I almost guarantee there is something inside the heater box with the core blocking the air flow.SyntheticBlinkerFluid wrote: Are you sure the HVAC panel is working properly? Did you actually take the core out? Could there be a possibility there is something in the core box blocking the air flow?The core has been in the truck since we bought it. Was replaced 3 months before we bought it. Heat has been E36 M3ty the whole time.
which means other than cutting a hole in the dash it has to come out.
In reply to MrChaos:
I havent pulled the heater core, but it is not leaking.
It's been reverse flushed about.... 20 times. Nothing, and I mean nothing has ever come out of it. Flow is free and clear.
No air in coolant lines. I have a high side fill installed.
I cut to do the blend door, but there's no cutting shortcut for the core itself.
If you're implying that the core wasn't changed, I can assure that's not the case. We bought the Jeep from my Haltech guy.
The blend door has been screwed up most definitely for years. I dunno. No berkeleying way in hell i'm taking the core out myself. So I guess the takeaway here is that i've done what I can and now I get to bend over and take it for a grand or so.
In reply to Swank Force One:
Honestly, you've done everything outside of the heater core. That's the last piece of the puzzle.
Get the IR thermometer. Check and see if the heater box itself is getting hot right where the core is.
I really feel like there is something restricting your airflow from the fresh air side of the core.
Is there someway to remove the cowl? Maybe stick a shop vac hose down there?
Wish I could help you out but I have no answers. My 99 XJ did the exact same thing and I never did figure it out. I also tried everything like you. Just never really got warm which sucked since I live in Michigan. It would barely defrost the front windshield. I bought it for a winter vehicle and I gradually quit driving it in winter because I was always cold. I no longer have the vehicle.
here are the main culperits of the lazy heat issue for post 96 XJ's
naxja said: Newer Cherokees do not have a heater control valve. Low heat can be caused by a lazy thermostat, a clogged heater core, a failing air blend door, or a water pump with a poor flow rate.
the only thing I see on that list that hasn't been addressed is the water pump which is only a 1-2hr job on a XJ/MJ iirc.
I did some web searching.. a lot of "fixes" seem to revolve around checking to make sure that the airflow around the heater core is ok. Owners seem to mention a ton of junk on the core, keeping the air from flowing through it and warming up
You'll need to log in to post.
