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Unread 01-04-2014, 06:19 AM   #1
angry_bird
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1999 WJ 
 
Join Date: Jan 2014
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Heat only when accelerating.

Hi guys, i am having a problem with WJ jeep 1999 4.7

The car is heating only when i am accelerating.
If the car is standing still on the parking lot, heater blows cold air.
If i am revving the engine from 1000 to 2000 and back, or accelerating the heater starts working.
When driving, heating works-ish.

I checked the water pump. It looks normal, nothing broken or weird about it.
Flushed the heater core, about 4 times. I've also changed coolant. Every time I do this, I also bleed the system to get air out. Every time i flush it, heating works little bit better. After few days starts getting worse.




Is there anything else to check????
When I bought the car 8 months ago I had a leak, so I've used stop-leak product.
Which was a mistake, but I am new to this car repairing.

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Unread 01-04-2014, 06:31 AM   #2
NotSoMelloYello
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2003 TJ Wrangler 
 
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Location: Coram, New York
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Most likely your heater core is clogged and needs replacing. If you've blown it out a few times already that means the gunk is so thoroughly attached inside the heater core that it won't come out.

You may also consider trying to replace the thermostat first because it is a much cheaper part and much easier to replace.

Heater cores are a bear to replace, most of the time requiring the removal of 50% or more of the dashboard.

Good luck!
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Unread 01-04-2014, 09:32 AM   #3
cde02ltd
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What you described is also what happens when you have a blown head gasket. Hope fully it is just a clogged heater core.
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Unread 01-04-2014, 09:45 AM   #4
NotSoMelloYello
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Quote:
Originally Posted by cde02ltd
What you described is also what happens when you have a blown head gasket. Hope fully it is just a clogged heater core.
A blown head gasket could cause the same but less likely if coolant level is staying consistent.
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Unread 01-04-2014, 10:35 AM   #5
cde02ltd
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Quote:
Originally Posted by NotSoMelloYello
A blown head gasket could cause the same but less likely if coolant level is staying consistent.
Good point, you would also see you temperature gauge spike up at idle.
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Unread 01-04-2014, 01:11 PM   #6
4Tom
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if you have pollen filter fitted check the filter. ( not fitted on all models )

If you have dual climate control there is heater flaps that regulate the air flow these might be sticking or broken

Do the self check of climate if there is a problem it will show error code. Site below will tell you how to put into test mode and what the error codes are.
http://www.wjjeeps.com/climate.htm
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Unread 01-04-2014, 01:45 PM   #7
three_jeeps
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My first suggestion is to change the thermostat - easiest (relatively) and cheapest.

I have used the stop leak stuff in the distant past, and had no adverse effects if were used correctly. I've seen ppl think that if one can will work, two will work better....not a good idea.

If you say you flushed the heater core and it gets a little better,then that seems to indicate that each time you flush you dislodge some of the junk in the core...but I still find it hard to believe that it would plug up the core that much if used correctly, unless the core is in a very bad state already...

I don't know about the blown head gasket related symptoms, but the cause-effect seems reasonable tho...notice any oil in the cooling water? foamy oil? if so, head gasket has a leak.
I'd also do compression check/leakdown test to see if head gasket blown.

If you used the stop leak to cure water from the heater core, then I'd say the core is bad and needs to be replaced (15-16 yo jeep?- heater core is probably dead).

If not, I'd then suspect the waterpump...changing both wp and thermostat is a 3-4 hr job, maybe less if you have done it before...
Changing the heater core is a PITA - much of the dash needs to be torn apart....there are you tube videos that show how to do this, that are pretty good.

All this assumes that the blend doors are functioning normally....


good luck
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Unread 01-06-2014, 09:49 AM   #8
angry_bird
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Thank you, for all your answers

I've also changed the thermostat, which was unnecessary. Old one was good, temp was constantly at 100C (212F)

We've replaced blend doors. Passenger side door was broken when i bought the car, so replacing the heater core will not be a problem.

Coolant level is staying consistent. There is no blue smoke from exhaust, so I think head gasket is good.

I'll check the pollen filter. First need to find out what it is and where is it located.

I've used one can of stop leak. Guess I've used it the wrong way. Last time the heater worked was when I've put in the stop leak.

Every time, I back flush it with compressed air. Need to apply quite strong pressure. Last time I put apple vinegar in the heater core overnight. There was a lot of gunk in the heater core when I flushed it.

There is no oil in cooling water.

It is a very weird problem. I cannot figure out what is wrong. I will change the heater core and then we will see if that helped.

The car has 143 000 miles

Any other suggestions??
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Unread 01-06-2014, 10:59 AM   #9
ZJPunk98
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clogged heater core or air in the heater core causing low flow. When you back flush, use water instead of air. Water pump could be going.
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Unread 02-25-2014, 05:28 AM   #10
angry_bird
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I've replaced the heater core and everything works fine. Looks like the heater core was in such bad condition it got clogged everytime i flushed it.
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Unread 02-25-2014, 01:11 PM   #11
86cj74.2L
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Quote:
Originally Posted by angry_bird
I've replaced the heater core and everything works fine. Looks like the heater core was in such bad condition it got clogged everytime i flushed it.
What was it clogged with?

Brown jelly?

Cut it open and find out.
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Unread 02-25-2014, 03:24 PM   #12
rdkendrick
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I'll probably get flamed for this, but here goes: http://www.dreamsofdrifting.com/ae86/heater/index.htm

http://www.reactionchemicals.com/coo...tem-flush.html

http://www.prestone.com/products/print/424?popup=1

Remember to fill it back up with only a mixture of HOAT (The pinkish stuff, Zerex G-05 or buy it from the dealer) and water. Do not use the green stuff.

Sent from my iPad using electrons
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