Heater Core? - JeepForum.com
 
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post #1 of 12 Old 08-21-2017, 05:44 PM Thread Starter
DrReaper
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Heater Core?

So my 98 5.9 will only blow hot air for a second after turning on the heat.

I have been around the block trying to figure out my heating issue. I have flushed the core several times and it did get better but not much. Last winter in Idaho it took 30 min to heat the jeep enough to drive it. I also didn't have to be at a job so I didn't need it everyday. I will be out the door early this year. It will be really cold as well.

I am facing replacing the heater core. I have been putting if off. Because it looks hard. Is there anyway I can test the core before taking the dash apart?

I have tested the air doors and they are opening and closing. When I flushed the core I took the return to a bucket and pumped it back through the core. I used some kind of detergent make for flushing cores. I let it run for 30 minutes and it got pretty hot from the pumping. It made little difference.

The flow seemed OK when pumping the cleaning solution through the core. That makes it confusing. Is it possible its clogged and can still flow OK?

I suppose I will figure it out when the dash it off lol

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post #2 of 12 Old 08-21-2017, 06:16 PM
wingless
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If the forced garden hose water flow through the heater core is good and if grabbing onto the heater core antifreeze hoses reveals them to be hot, then the heater core is getting hot.

If the heater core is getting hot but the cabin is not getting heat, then there is not airflow through the heater core. Either the heater core fins are obstructed, such as covered in leaves, or the blend door is diverting air to not flow through the heater core.

On my vehicle all of the collected vegetation was against the evaporator.

My guess is the blend door the the problem.


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post #3 of 12 Old 08-21-2017, 06:50 PM
StPaul59
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A 205 stat helps. I run it year round with no problems.
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post #4 of 12 Old 08-21-2017, 08:58 PM
RedRiverT
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"If the heater core is getting hot but the cabin is not getting heat, then there is not airflow through the heater core. Either the heater core fins are obstructed, such as covered in leaves, or the blend door is diverting air to not flow through the heater core."

That's the key, is the heater core getting hot? You might have the "air lock" problem where an air bubble in the heater core exit tube is only allowing a trickle of flow to get by. You turn it on, then all heat in the heater core is sucked out and it isn't flowing enough hot coolant to give off much heat. If you didn't do something to ensure you got the air out when you flushed it, take off both heater core hoses and hold them up, them pour coolant or water down each one, letting it overflow a quart or so into something. With them both full, work the ends up & down alternately to move the water back & forth through the core. This got the bubble out of mine and viola!, I had heat.

EDIT: Oh yeah, this happened after I flushed it with a garden hose. It got air trapped.
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post #5 of 12 Old 08-21-2017, 11:50 PM
Uniblurb
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You make want to check to see if your blend door motor is working or turning the center collar. Below is a photo of the motor and while this is for ATC the manual system has it in the same place.

http://www.jeepforum.com/forum/f13/z.../#post14155615

And it you do see it turning remove the motor and make sure the blend door shaft isn't broken. You only have to remove the 3 larger screws and I used one of those smaller 90* bent screwdrivers for the back screws.

PS. what a shame those photobucket photos are missing and KoreaZJ had some real good photos of the cracked nylon gear inside the housing.

If you do end up replacing the heater core believe I'd replace the evaporator at the same time while you have the dash apart. Good luck.

96 4.0 ZJ Laredo, 2004 4.7L WJ Limited, 96 4.0 XJ (son's)


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post #6 of 12 Old 08-24-2017, 12:16 AM
phitmein
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Have you burped your system ?

Not enought water/coolant in it can cause the same problem .
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post #7 of 12 Old 08-25-2017, 09:59 PM
papitt
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iS THERE A GOOD you tube video for changing the heater core.
Or some know all the problems.
& Tool sizes .. I believe I;VE GOT ONE TO SWAP OUT.
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post #8 of 12 Old 08-26-2017, 10:21 AM
RedRiverT
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Quote:
Originally Posted by papitt View Post
iS THERE A GOOD you tube video for changing the heater core.
Or some know all the problems.
& Tool sizes .. I believe I;VE GOT ONE TO SWAP OUT.
I did mine last winter, a '97, so a little different than your '95. I deleted the threads I had saved. Do a search on here. There is a thread that I remember which was for the early models.

I used the "cut the plastic stiffener" shortcut method instead of removing a lot more of the dash. I didn't butcher the plastic and was thinking I would make some little brackets and bolt or rivet it back in, but after I got it out, I saw what little difference it made, so simply left it out. (This might not apply to your '95.)
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post #9 of 12 Old 09-04-2017, 12:05 PM Thread Starter
DrReaper
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It's working now!!! So I fixed it by purchasing two long funnels. Disconnected both lines to the core. Attached the funnels and filled them. Worked them up and down and bubbles came out. Just like RedRiverT suggested. I tried burping the core before with no success, the funnels made all the difference. Thanks for all the reply's. No more hour trips to the store at 10 degrees! man that was cold last year.
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post #10 of 12 Old 09-04-2017, 09:06 PM
speedbrake
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I did a forum write up for changing the heater core, lots of pictures, a while back for my 94 ZJ. Here's the link:
http://www.jeepforum.com/forum/f13/9...45/?highlight=
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post #11 of 12 Old 09-04-2017, 09:08 PM
kg6mov
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Quote:
Originally Posted by speedbrake View Post
I did a forum write up with lots of pictures a while back for my 94 ZJ. Here's the link:
http://www.jeepforum.com/forum/f13/9...45/?highlight=
OP's got a 98 with a totally different dash and heater core.


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post #12 of 12 Old 09-04-2017, 09:50 PM
speedbrake
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Agreed. OP has a 98. I threw the link in there for papitt (post #7), who asked if there was a good YouTube video for changing the heater core in his 95 ZJ.
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