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Unread 11-21-2014, 08:00 PM   #1
w103tws
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1998 XJ Cherokee 
 
Join Date: Nov 2011
Location: Venedocia, ohio
Posts: 11
Hours of work and still poor heat

Ok, so I just picked up a very nice 1998 4.0l xj. I knew the heat was weak when I looked at it, but didn't think much of it. Since then, I've spend 10's of hours reading and working on this thing trying to get decent heat.

-I flushed the heater core with Hot water both directions multiple times, several different days. There is good flow, the garden hose flows well through both hoses and I can blow through it without a problem. Not much gunk came out. This helped a little

-I've also filled the core up with CLR and let it sit for an hour on 2 different occasions and flushed again with hot water. Everything came out nearly clean. This helped a barely noticeable amount.

-replaced the thermostat. This did nothing

-burped the whole cooling system of air. this did nothing

-Top heater core hose gets too hot to hold, bottom one is hot, but can hold it.

-Took blend door motor out and it makes the full range of motion just fine, twisted the blend door shaft with finger and can turn it full range of motion. When turning the knob, I can feel the temperature change in the vents.

-Temp gauge runs up to 210 then comes back to 195 and stays there pretty much the whole time.

In the beginning, the heat was almost nonexistent. Now I get piss-warm heat depending whether I'm idling or driving down the road. At least now I can defrost my windshield, but come on, It should be better than that.

The only thing I haven't done is check the water pump. Is it possible that if the impeller is completely corroded away, it may not be pushing the coolant through the heater core? but then, why are both core lines hot?

I am at a standstill on this one, I really don't know where else to go, and I really don't want to give a dealership free rein of my checkbook.

Any help is appreciated. Thanks

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Unread 11-21-2014, 08:35 PM   #2
Nor10
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1992 XJ Cherokee 
 
Join Date: Aug 2007
Location: Pennsylvania
Posts: 38
I just read in the FSM that a weak or failing water pump can not pump the coolant through the heater core. That is one of the checks for diagnosing water pump failures. I will try and find the specific wording.
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Unread 11-21-2014, 08:38 PM   #3
w103tws
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1998 XJ Cherokee 
 
Join Date: Nov 2011
Location: Venedocia, ohio
Posts: 11
Thank You, But...

I just contacted the previous owner and verified that in 2010, the dodge dealership flushed the radiator and replaced the water pump, so I guess that is more than likely not the issue.
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Unread 11-21-2014, 08:40 PM   #4
Nor10
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1992 XJ Cherokee 
 
Join Date: Aug 2007
Location: Pennsylvania
Posts: 38
From the diagnostic chart for low heat output:

5. Water pump is not pumping
water to/through the heater core.
When the engine is fully warmed
up, both heater hoses should be
hot to the touch. If only one of the
hoses is hot, the water pump may
not be operating correctly or the
heater core may be plugged.
Accessory drive belt may be
slipping causing poor water pump
operation.
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Unread 11-21-2014, 10:01 PM   #5
1stockjeep
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1993 XJ Cherokee 
 
Join Date: Feb 2009
Location: modesto CA
Posts: 849
If the motor doesn't overheat I don't think the water pump is the issue, have u checked to make sure the blend doors actually function the proper way with jeep running? Sounds like cold air is stil getting in.
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Unread 11-21-2014, 10:47 PM   #6
MaskedMallard
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2000 XJ Cherokee 
 
Join Date: May 2009
Location: MN
Posts: 225
Quote:
Originally Posted by 1stockjeep View Post
If the motor doesn't overheat I don't think the water pump is the issue, have u checked to make sure the blend doors actually function the proper way with jeep running? Sounds like cold air is stil getting in.
Does the environmental system cycle??? Can you cycle the air from the defrost/windshield to the floor??? Can you feel the air change in force as you cycle the knob???
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Unread 11-22-2014, 09:03 AM   #7
CCKen
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1999 XJ Cherokee 
 
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Location: Canton, MI
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Quote:
Originally Posted by w103tws View Post
Ok, so I just picked up a very nice 1998 4.0l xj.Took blend door motor out and it makes the full range of motion just fine, twisted the blend door shaft with finger and can turn it full range of motion. When turning the knob, I can feel the temperature change in the vents.
New one on me. I thought the 98 had the push-pull cable mechanism for the blend-air door, like in the pics below, and that the servo motor blend-air door actuator didn't come out until 1999.



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Unread 11-22-2014, 09:16 AM   #8
el-macho
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Join Date: Nov 2014
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try this!

Ok, just inheritted a 1997 xj 4.0... 5 spd... yehaaa, the heat sucked also, well lets put it this way, it was overheating in the summer, i checked the rad situation and it was still intact but all that was left of the rad were the horizontal aluminum lines, the ribs between were all gone, so i got a new rad and at the same time i eliminated (ripped out) the condenser (ac rad in front of regular rad), what this did is provide over efficient cooling for the motor, even in 25 celcius plus weather my temp gage did not go above half, it always stayed on the cooler side of the temp reading (left of half), at about 1/4 !! I knew this would be an issue in the winter!! I knew i would get poor heat, so I also flusthe the the heater core w clr, but i let it sit at least for 24 hours, (this is important!!) two hours is not all that sufficient, i actually wish i had it soaking for two days... as a whole bunch of deposits came out after 24 hours and it is iportant to flush it both ways, back and forth a few times. I knew that having the condenser removed, there would be too much cold air getting rad, so i fabricayted a rad blocker from a piece of lexan.... acrylic... whatever you have but just dont block it with red neck cardboard, it looks like garbage and will rot with moisture, i left a space of about an inch all the way around so i would not block the rad completely and i drilled holes in it, about ten one inch holes... i would tape them up and later figure out how many to open or close depending on how the engine is cooling... Anyway final verdict it that i have good heat... not great but much much better, temp gauge is at half where it should be, i am now realizing that i should have made the piece of lexan a little bigger blocking of the rad completely since i want a little more heat... but it is nice and warm... nothing like a new car warm but nice... i want more heat so i will fabricate a bigger piece of lexan first. Important to attach the rad blocker away from the rad in a way the condenser was oringally.. i mounted mine to the grille support. Not sure if this will provide any valuable info to you... if you still have the condenser than i would let clr sit much longer than two hours and flush both ways, water pump propeler missing a blade will only cause the coolant to not flow as much and result in even hotter situation so that is not your problem, i would flush the whole system, bleed it properly (sometimes air bubbles will cause this problem), and either get a new core (dont envy the labout though), or flush the old one again... Hope this helps. I will become a member and take some pictures of my setup. (the rad blocker also keeps the dirt out when booking throgh fields, mud and such).

Martin
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Unread 11-22-2014, 09:18 AM   #9
el-macho
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Join Date: Nov 2014
Posts: 3
heat issue

Ok, just inheritted a 1997 xj 4.0... 5 spd... yehaaa, the heat sucked also, well lets put it this way, it was overheating in the summer, i checked the rad situation and it was still intact but all that was left of the rad were the horizontal aluminum lines, the ribs between were all gone, so i got a new rad and at the same time i eliminated (ripped out) the condenser (ac rad in front of regular rad), what this did is provide over efficient cooling for the motor, even in 25 celcius plus weather my temp gage did not go above half, it always stayed on the cooler side of the temp reading (left of half), at about 1/4 !! I knew this would be an issue in the winter!! I knew i would get poor heat, so I also flusthe the the heater core w clr, but i let it sit at least for 24 hours, (this is important!!) two hours is not all that sufficient, i actually wish i had it soaking for two days... as a whole bunch of deposits came out after 24 hours and it is iportant to flush it both ways, back and forth a few times. I knew that having the condenser removed, there would be too much cold air getting rad, so i fabricayted a rad blocker from a piece of lexan.... acrylic... whatever you have but just dont block it with red neck cardboard, it looks like garbage and will rot with moisture, i left a space of about an inch all the way around so i would not block the rad completely and i drilled holes in it, about ten one inch holes... i would tape them up and later figure out how many to open or close depending on how the engine is cooling... Anyway final verdict it that i have good heat... not great but much much better, temp gauge is at half where it should be, i am now realizing that i should have made the piece of lexan a little bigger blocking of the rad completely since i want a little more heat... but it is nice and warm... nothing like a new car warm but nice... i want more heat so i will fabricate a bigger piece of lexan first. Important to attach the rad blocker away from the rad in a way the condenser was oringally.. i mounted mine to the grille support. Not sure if this will provide any valuable info to you... if you still have the condenser than i would let clr sit much longer than two hours and flush both ways, water pump propeler missing a blade will only cause the coolant to not flow as much and result in even hotter situation so that is not your problem, i would flush the whole system, bleed it properly (sometimes air bubbles will cause this problem), and either get a new core (dont envy the labout though), or flush the old one again... Hope this helps. I will become a member and take some pictures of my setup. (the rad blocker also keeps the dirt out when booking throgh fields, mud and such).

Martin
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Unread 11-22-2014, 09:49 AM   #10
LaddieHanus
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1997 TJ Wrangler 
 
Join Date: Nov 2009
Location: Nederland, Colorado
Posts: 211
On my 97 TJ I did everything in the first post. I also replaced the radiator due to a leak and replaced the water pump at the same time thinking it might fix the heat problem. Turned out the impeller had rusted way on the water pump. Still had poor heat. Did the CLR treatment and a little improvement that lasted the winter but the next was cold again.

A couple of weeks ago I did the CLR treatment for the third time and ended up with a lake on the passenger side floor.

Long story short it took 2 days to pull the heater core and replace it. Used the Spectra core ($40 from amazon compared to $300 for the Mopar one) and I dont remember the heater putting out that much heat.

The TJ and XJ use the same core and the heater system is similar.
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Unread 11-22-2014, 12:52 PM   #11
w103tws
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1998 XJ Cherokee 
 
Join Date: Nov 2011
Location: Venedocia, ohio
Posts: 11
Thanks for the responses.
I am able to change the position that the air blows to just fine, and regardless of what position its set on, I am still able to regulate the amount of heat that comes out. I found out the water pump was replaced 4 yrs ago, so I really doubt the impeller could be rotted away. I can let the jeep idle all day, and it won't get a hair over 210, it's almost always under a little, so that makes me think the water pump is function fine. On a side note, I can grab and squeeze the upper radiator hose very easily, it's hot, but I figured it would be hard and full of pressure, but its not, it's very squishy. Same with the heater core hoses. If I take the radiator cap off when running, I can tell that coolant is circulating because the water level surges a bit.

I feel that If I do another CLR treatment, I may be pushing my luck and end up with a leak. If that happens, I'll be asking around for estimates on replacing the heater core.

The only thing I can think of now is that the fins on the outside of the heater core may be clogged with dust, dirt, hair, gunk, and not allowing air to pass through it. Is there any way to get an air compressor nozzle in there to try and blow it off without tearing into the dash? Can I cut a hole in something to access it?

Thanks again for reading
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Unread 11-22-2014, 04:28 PM   #12
Jeepguy4276
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Join Date: Apr 2013
Location: Fargo, North dakota
Posts: 344
My low heat ended up being the waterpump.
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Unread 11-22-2014, 04:45 PM   #13
Nor10
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1992 XJ Cherokee 
 
Join Date: Aug 2007
Location: Pennsylvania
Posts: 38
Dont assume your water pump is not at fault just because its been replaced 4 years ago and you dont over heat. The FSM clearly states the water pump could be the reason for low heat output. Here are the water pump diagnostic tests. It costs nothing if you catch your anti freeze.

WATER PUMP TESTS
LOOSE IMPELLER
DO NOT WASTE reusable coolant. If solution is
clean, drain coolant into a clean container for reuse.
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR
DRAINCOCK WITH THE SYSTEM HOT AND UNDER
PRESSURE. SERIOUS BURNS FROM THE COOLANT
CAN OCCUR.

(1) Drain the cooling system.
(2) Loosen the fan belt(s).
(3) Disconnect the lower radiator hose from the
water pump.
(4) Bend a stiff clothes hanger or welding rod as
shown in (Fig. 2).
(5) Position the rod in the water pump inlet and
attempt to hold the impeller while turning the fan
blades. If equipped with a viscous fan drive, turn the
water pump shaft with a breaker bar and socket attached
to a mounting flange nut. If the impeller is
loose and can be held with the rod while the fan
blades are turning, the pump is defective. If the impeller
turns, the pump is OK.
Connect the hose and install the coolant, or proceed
with repairs.

INSPECTING FOR INLET RESTRICTIONS
Inadequate heater performance may be caused by a
metal casting restriction in the water pump heater
hose inlet.
DO NOT WASTE reusable coolant. If solution is
clean, drain coolant into a clean container for reuse.
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR
DRAINCOCK WITH THE SYSTEM HOT AND UNDER
PRESSURE. SERIOUS BURNS FROM THE COOLANT
CAN OCCUR.
(1) Drain sufficient coolant from the radiator to decrease
the level below the water pump heater hose
inlet.
(2) Remove the heater hose.
(3) Inspect the inlet for metal casting flash or
other restrictions.
Remove the pump from engine before removing
restriction to prevent contamination of the
coolant with debris. Refer to Water Pump Removal.
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Unread 11-22-2014, 04:53 PM   #14
MaskedMallard
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2000 XJ Cherokee 
 
Join Date: May 2009
Location: MN
Posts: 225
Quote:
Originally Posted by w103tws View Post
Thanks for the responses.
I am able to change the position that the air blows to just fine, and regardless of what position its set on, I am still able to regulate the amount of heat that comes out. I found out the water pump was replaced 4 yrs ago, so I really doubt the impeller could be rotted away. I can let the jeep idle all day, and it won't get a hair over 210, it's almost always under a little, so that makes me think the water pump is function fine. On a side note, I can grab and squeeze the upper radiator hose very easily, it's hot, but I figured it would be hard and full of pressure, but its not, it's very squishy. Same with the heater core hoses. If I take the radiator cap off when running, I can tell that coolant is circulating because the water level surges a bit.

I feel that If I do another CLR treatment, I may be pushing my luck and end up with a leak. If that happens, I'll be asking around for estimates on replacing the heater core.

The only thing I can think of now is that the fins on the outside of the heater core may be clogged with dust, dirt, hair, gunk, and not allowing air to pass through it. Is there any way to get an air compressor nozzle in there to try and blow it off without tearing into the dash? Can I cut a hole in something to access it?

Thanks again for reading
Start with a known good radiator cap & see what happens. The URH should be firm & also, it is not a good idea to open a pressurized cooling system when hot. I believe the radiator cap should be around 15psi. It's stamped on the cap. Just because it says it's rated at 15psi, doesn't mean that it is. Find out if you can test the new cap.
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Unread 11-22-2014, 05:32 PM   #15
w103tws
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1998 XJ Cherokee 
 
Join Date: Nov 2011
Location: Venedocia, ohio
Posts: 11
Great ideas guys! Ill get on it ASAP

Thanks!!!
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