Very little heat- Diagnosing the source of the problem?

WheelNut

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Hi guys,

First post here! I recently bought a $1000 KJ as my first 4x4 and she's a bit rough around the edges! I was looking for a nice XJ, but of course finding a 2-door manual that isn't wrecked is impossible and the KJ was definitely in my budget. Also, who doesn't like a project?! Oh, and I can scratch up the KJ in the bush without any worries.

The problem:
Very weak heat from the HVAC system! There IS a difference in heat from full cold to full hot, but it is weak. The heat is like dog breath (minus the stink). Not enough to stay comfortable that's for sure.

Fixes thus far:
- I found the coolant hoses running to the heater core were dead cold and the aluminum pipes they attach to were also cold up to half way through. I removed the hoses and blasted them with water and now they flow well. The heater core hoses were still cool though, but at that point there was a tiny bit of heat in the cabin.
- Today I flushed the heater core and now the hoses going to the core through the firewall are piping hot, but the heat in the cabin has only improved by a couple degrees. Perhaps the heater core is partially clogged and is only heating in a certain area? The water flow through the core seemed to be pretty good from what I could tell.

Operation notes:
- When the fan is set to "4" the air from the vent is barely warmed. At fan setting "1" there is noticeable heat from the vents.
- This heat issue persists across all vent settings except in the AC settings where the temperature drops a bit.
- The heat can indeed be adjusted from cold to hot and the cold is indeed cold, but the hot is just lukewarm. There is a difference in the sound of the airflow between the hot setting and the cold setting, so something is happening in there.
- Temperature gauge on the cluster is dead on center. The engine seems to be heating properly. Upper rad hose is hot.

Conjecture and Questions:
- I would *guess* that the heater blend door actuator is possibly malfunctioning, or maybe it is the blend door? Could the blend doors be broken? Do the blend doors on the KJ break often like they reportedly do on the WJ?

PS:
Thanks in advance for any help! I'm pretty excited about this Jeep. I bought it on a whim and thought it was a bit puffy and silly at first, but after digging into it a bit I'm really stoked on this thing actually. I'm coming from owning an E36 BMW (my current daily) and a Mini Cooper, so this is a real strange beast to me and I can't believe how beefy it is built! I found the build sheet for my KJ amongst the service records and was super stoked to see it has the tow package and the Trac-Lok LSD! I've got a whole bunch of parts on order to refresh all the fluids and basic maintenance stuff. Hoping to get this thing reliable enough to go off into the forest this summer! Lots of cleaning to do too and I'll be repainting the rims bronze.
 

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LibertyTC

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Welcome, Nice Jeep. It it an 04?
Hope there is nothing wrong with the blend door, you may just have trapped air..
Lower rad hose & new thermostat installed yet? Use This one only.
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With the cooling system now flushed, try bleeding the air out when hot.
Downward force, counterclockwise a bit, and paper towels handy, let it leak out a bit, til no bubbles seen/ then close/ tighten it.
Don't use an allen key. It's hard to break free.
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Cold in the AM overnight, fill to the middle of reservoir tank/cold line.
Monitor for a few days & only use HOAT or Zerex G-05 coolant !
Kj' Jeeps have plastic water pump impellers, never use the wrong coolants.

Do you have the owners manual ? Looked in the glove box up top for it? Good reference for fluid + specifications.
Once I know what year your Jeep is, will get you the pdf online Factory service manual.

Trac-Lok rear diff requires adding a 4 oz bottle of Mopar Limited slip additive.
I use Lucas Dino (not synthetic) gear lube + the 4 oz bottle.
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WheelNut

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Thanks so much Liberty-TC! That is a great collection of tips. Sorry, I should have posted the year! 2002 I do have the owner's manual, the '02 FSM, and the '03 parts list (couldn't find '02 parts guide). I have not yet changed the thermostat or lower rad hose yet. I'll order those up today. My bleed port seems to be stripped. I'll get the old one out somehow and install it along with the T-stat.

I ordered Redline 75W140 synthetic with friction modifier already in it. I thought about the Mopar stuff, so hopefully this Redline will be okay.

Mopar PCV is on the way, as is new belt tensioner, new rad cap, new belt, new air filter, new rear glass struts, new front prop shaft, Jeep adapter for the Motive brake bleeder, and...I think that's about it right now haha. Lots more little things to do and diagnose coming still.
 

LibertyTC

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For now I'd leave the stripped hex alone and focus on ensuring that your jeep does have the Mopar thermostat installed.
It has the built in air bleed and will assist in hopefully getting you some decent heat soon.
Sounds like you have done some home work, the 02 fiche is MIA, and the 03 is close enough.
The rear diff fluid should be changed every 20k. It is best to use dino gear lube as it sticks best to gears, compared to synthetics.
I have also have a trac-lok & the mopar 4 0z bottle works well.
You should be just "fine with the red line" lol, as it has the friction modifier built in.
Still consider dino gear oil next swap out & the 4 oz bottle.
Keep up the good work & you will have a good KJ soon!
How many miles or Km's on the Jeep now? Any rust?
 

WheelNut

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Thanks, I'm hoping to have this thing running great soon! Can't wait to drive it on some rocks :D

It has 240,000km (150,000mi). The body is really in pretty decent shape. One big dent in the rocker panel and some minor rust on the bottoms of the doors. A bit of rust on the rear upper control arm triangle, but pretty darn clean overall. Vancouver is really easy on steel, so I'm lucky there. The Jeep was a owned by a guy who bought it off a friend who had to quickly move back to England and he didn't maintain it AT ALL. It was missing 2.5L of oil when I bought it, which certainly made me very afraid, but the engine sounds good, and his friend he bought it from maintained it well, so *fingers crossed* it'll be okay. I actually brought 2 quarts of oil with me for the test drive o_O The neglectful owner only had the Jeep for a year and put about 7,000km (5,000mi) on it.
 

LibertyTC

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Folks who don't maintain their jeeps, then allowing a low oil condition, are immediately placed on the naughty list. Good for you on topping it up !
Great that it runs well, any smoke on start ups? Keep that oil & filter clean. It is the single most important lifeblood of an engine, as I'm sure you already know! ;)
240km is not bad, & when it comes to cooling, ensure that the electric fan works well. When A/c is engaged the fan should be working.
You should have a nice camping rig all set up for summer!
 

tommudd

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Thanks so much Liberty-TC! That is a great collection of tips. Sorry, I should have posted the year! 2002 I do have the owner's manual, the '02 FSM, and the '03 parts list (couldn't find '02 parts guide). I have not yet changed the thermostat or lower rad hose yet. I'll order those up today. My bleed port seems to be stripped. I'll get the old one out somehow and install it along with the T-stat.

I ordered Redline 75W140 synthetic with friction modifier already in it. I thought about the Mopar stuff, so hopefully this Redline will be okay.

Mopar PCV is on the way, as is new belt tensioner, new rad cap, new belt, new air filter, new rear glass struts, new front prop shaft, Jeep adapter for the Motive brake bleeder, and...I think that's about it right now haha. Lots more little things to do and diagnose coming still.

Toss that synthetic crap back on the shelf
Regular dino does much better in the diffs
 

Duster

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Well I came to say it is probably air in the system. In my experience these engines can be very odd about air trapping. First time I ever did anything with the cooling system I had a heck of a time. Absolutely tried every old trick I knew of trying not to touch that bleed for fear mine was gonna strip. Once I realized I was not going to get the air out and gave in I was able to get it out without stripping. That got it right out.

There have been other times since that I had no problems and didn't have to use it. I wasn't aware of the thermostat. I have never changed mine and knew nothing about the air bleed? I guess it is possible it was plugged when I had the worst trouble. I was into the cooling system because I had taken it to a dealer for the mileage service because it was due transmission fluid and filter service. I saw there was no drain on the pan so I just took it in. I think it was trans, spark plugs and coolant change on that mile marker. My red coolant looked orange in the tank of my 2007. Whoever did the work just drained the tank and refilled with orange. Didn't drain the system. Heck I thought it used the orange too but had never added any. When I had problems very shortly afterwards and went for the supplies the guy was like no that is the wrong coolant to put back. I was like well that's what has always been in it. But when I got home to do the work and opened the radiator cap I was like HOLY COW! Guy is right and that is how I figured it out. In the radiator I had red coolant with what looked like oatmeal or some **** in it. MIXED COOLANT.

These indeed use the Mopar Hoat Red coolant. So I recommend that. In my case it was the weekend so I went to Zerex G 05 hoat. I have had no issues with that and it is fine with me. Its sorta golden or yellow in color. Don't go by color. Go by formula. Some of the asian formulas are red too and NOT the right formula. Mopar Hoat Red and Zerex G-05 hoat are the only two I have used and can recommend. I had done a full flush, refill with distilled, then flushed and refilled with the Zerex due to the cross contamination.

Anyways, since yours is stripped out, you can try my old tricks which usually work without opening a bleed. Back it down a hill or drive it up on some ramps while cold. Put the heat on, lift hood, remove cap and let it run a while. You will not notice a strong circulation. Sit where you can see the filler neck and give it a little throttle. This way you can see when to let off. Do that for a bit until the temp comes up and hope you start to feel some roasting heat. The idea is to get the heater core low and try to get the air to purge.

Also, you can set the fan to low and move the temperature dial. Sometimes you can hear the motor and parts moving. I'm thinking as mine has aged I can hear the temp one and air position one move too.

What color was the coolant that came out of this jeep and how did it look?

Guys do you think his issue may be the air bleed on the thermostat being plugged? I didn't know it existed. Might have been why I had so much trouble removing the trapped air my first time when I was contaminated, and is easier now because it cleared itself. Either way glad I know to get a Mopar thermostat if mine ever sticks.
 

WheelNut

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The coolant was orange. When I bought it I had the shop across the street do a drain and fill and they used Prestone orange (Dexcool OAT). I bought some more of this Prestone to refill after I install the new thermostat and bleeder screw. I just picked those two parts up from the dealer a few days ago, so I'm hoping to get them into the truck asap. Maybe I should just go pick up some Zerex G-05 so I'm not worrying about getting the wrong stuff. HOAT is tough to find! I'm going to need so many empty bottles to get rid of all this spent coolant haha.

The coolant wasn't goopy at all, but it did have a small amount of rusty looking chunks in it. Any thoughts on flushing with cooling system cleaner?

Another thought: The Prestone bottle says it meets Chrysler MS-9769 spec, which the Zerex G05 also lists. MS-9769 can't be HOAT necessarily though can it? There were a number of bottles at the store that showed MS-9769. The FSM calls out MS-9769 as being the correct coolant, but from what I see online MS-9769G is HOAT and MS-9769 is OAT.
 
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Duster

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HOAT is what you want to use in these.

I don't know that what you are using would cause problems if it was a 100% all OAT fill. If any old was left in the system it's very likely your problem. When HOAT and OAT meet it makes a mess. Could clog something up.

If your blend doors are working you most likely have some air trapped or something clogged up. Your heater core may be partially clogged for example.
 

tommudd

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Remove hoses, thermostat, lines to heater core etc and flush everything very good
Then start back over and get everything back together with HOAT coolant
then bleed the system well and go from there

While you have it apart get some good cleaner in to the heater core and let it sit for a few hours, flush, repeat
 

Duster

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Tried to upload a picture where I had a small mixture, which in my case happened from someone filling the reservoir tank with OAT, so it was easy to see at the radiator filler neck on my 07.

However it says it's too large when I try. Doesn't even say what the size limits are as far as pixels or file size? Anyone got a clue?
 

LibertyTC

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1024 X 768 is best- or up to 1600 x 1200 should work.
 

Duster

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Thanks, that took a couple tries.
 

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WheelNut

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Hey guys, thanks for all the replies so far!

I drained the system by pulling the lower rad hose this evening. The draincock drain only dribbled, so I guess it is clogged up. I took the upper rad hose off to have a look and the inside of the radiator looks like it has been flushed with orange paint and the inside of the upper rad hose is all gritty inside (not so orange though). I've attached a couple images (the inside of the heater hose looks really strange as I had a light shining into it from the far side).

So, looks like some serious flushing is in order. My question is how do I do it? Re-fill with distilled water, run the engine to let it cycle, top up, and then drain and repeat a couple times? I need to watch some Youtube videos to see how some other folks are doing it as I don't have the tools to follow the FSM's pressurized flush method. Removing the hoses to flush them won't be too hard and I'm taking the thermostat out anyway.

I also need to figure out how to get the clutch fan+ HD shroud out...Once I get the fan clutch loose how is the shroud removed? It seems to be constrained by the upper radiator support on the frame. Hmmm...
 

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uss2defiant

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I drilled out the rivet that holds the horizontal support to the vertical support and replaced it with nut and bolt.
I think there's another method as well that someone else would chime in.
once separated, the horizontal piece is held in by two bolts on either side.

If you haven't had it professionally flushed, it might be good to do that.

The poor man's way is to use a garden hose and flush as much as you can.
Flush the heater block as well.

Then use a off the shelf coolant flush additive from your LAPS.

Run it for a bit with the t-stat out, you'll need the gasket installed w/ the housing to maintain a seal.
Drain and repeat until clear with DI water.
Keep in mind that you're using water so don't keep pure water in there too many days or corrosion will start.

After that, just add the appropriate amount of 100% HOAT to make you 50/50 mixture.

Total coolant is 14 quarts.

while you're at it, might as well replace the radiator hoses.

it also might be a good investment to change the radiator too.
 
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WheelNut

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I picked up 2 gallons of Zerex G-05 yesterday. I feel like taking on this flushing task is really daunting, but I think that is just because I have very little experience working with cooling systems. I just have to tell myself this is an opportunity to learn! Good thing I don't really need to drive this Jeep until April, so I've got lots of time to make mistakes, haha!
 

uss2defiant

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also don't forget to cut that notch in the fan shroud. that way you can remove the shroud without needing to remove the viscous fan.
 

Duster

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I picked up 2 gallons of Zerex G-05 yesterday. I feel like taking on this flushing task is really daunting, but I think that is just because I have very little experience working with cooling systems. I just have to tell myself this is an opportunity to learn! Good thing I don't really need to drive this Jeep until April, so I've got lots of time to make mistakes, haha!

It's not a big deal job. It's pretty simple if you want to do it yourself. I recommend a lot of gallons of distilled water to refill, Bleed the air out. Put the cap on. Drive around some. Come back, let it cool so it doesn't spew on you or burn you. Drain, repeat. It is a pretty high capacity system so it moves a lot out so long as it is not to the point of stuck in there. Repeat until the distilled water comes out clean.

I don't know where you live. But if you are in a freezing temperature area, of course make sure you don't let it "cool" overnight because you have no antifreeze and don't want it to freeze and crack your engine etc.

And I personally would just drain all the water out the last time and add coolant. Some do the 50/50 premix and that is fine if that is what you have. Just be aware a good bit of water remains in the block unless you take effort to get it out... like jacking up the rear end. So if you are using 50/50 and live in a crazy cold climate or crazy hot one your mix won't turn out 50/50. So you'll want to used one of the little mixture and freeze/boil testers after when you find you can't get 14 quarts in. That way you can test and see if you are OK for your area.

This is not an ordeal if mixing your own, you can pour 1 gallon to 1.5 gallons of 100% coolant in, then start your mixing. Point though is start out with coolant to mix with the water that says.

Typically, best I can remember I can only get 2 gallons in if I don't go to trouble to try to push the water out. This last time I did a water pump gasket and radiator replacement I bought 3 gallons of 50/50 premix but only used 2. It hadn't been all that long so I didn't bother with a water flush. Anyways that also tells me if the system is 14 quarts, about 6 quarts stayed in the block with the radiator removed and water pump off (with the thermostat in).

In times past I have jacked it up, and I have also been a redneck and poured coolant into it to push the water out until I could feel and smell the coolant with the finger test coming out the bottom hole. That turned out fine too. It was a 50/50 mix when I tested it.

Best I remember, when mine was cross contaminated mixed, I drained it, then poured water through it until it came out clear as I had Mopar Red in at the time. Then filled, ran, drained 2 or 3 times with distilled water. Then just filled with 50/50 not caring the mix was off (because it was still safe for my climate at the time) so that I could drive it a few days and check to see if there was any more sign of reaction... and there was. So then I drained really well and refilled.

Nothing showed up much after that. A little bit by the filler neck I kept sucking out with an old turkey baster I stole out of the kitchen ;)
 
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