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Unread 04-01-2009, 10:00 AM   #1
Nburns24
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01 wj 4.0 overheating still!!!

I am new to the forum and to jeeps, but I gotta say this forum is a wealth of information. My issue is that I've been having heating issue's since I got the jeep 3 months ago. The heat didn't work at all when I first got the car then after a couple flushes by the dealer it worked ok but not as hot as it should have been. The other day on my way to work I had no heat and my temp. gauge rose almost into the red. On my way home it did rise into the red and I had to pull over a few times let it cool down, then drive a little more. Since then, I have replaced the water pump, thermostat, and radiator. IT IS STILL OVERHEATING!!! The only thing that I can think of is the heater core but I don't want to jump into that unless it is absolutely necessary. How can I diagnose this?

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Unread 04-01-2009, 11:09 AM   #2
blovingier
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I would say that you ought to take the heater hoses (running into and out of the firewall) and disconnect them and then hook a garden hose up to one line going into the heater core and run water through there. My bet is on your stealership just doing a really crappy job of flushing your system. If you changed out everything else, then it pretty much has to be your heater core, but if it's not leaking, then it's probably just clogged. In my opinion, you've already spend hundreds of dollars on everything else, what's another $135 for a heater core. Then you will know that you are working with all new parts and can start fresh with all new coolant and then make sure to do regular flushes (on your own, it's easy) and maintain your coolant system to keep from having further issues later on.
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Unread 04-01-2009, 11:33 AM   #3
Nburns24
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That's what I figured I would have to do, just wanted to make sure there was nothing else that could be going on...If I can't unclog it, is there any danger in bypassing it so I can get to work and if not whats the best way to do that?
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Unread 04-01-2009, 04:58 PM   #4
Nburns24
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so I flushed the heater core and a little bit of brown stuff came out but it was not blocked, After running for a while the top of the hose that goes from the water pump to the top of the radiator was only warm on the first half of the pump coming out of the radiator. I pulled the hose and theres no blockage in it. Could my water pump be no good, I just replaced that and the thermostat two days ago....I really gotta fix this I had to call into work today and can't afford to keep calling in because of my jeep, any thoughts???
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Unread 04-01-2009, 05:20 PM   #5
dougy147
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Is your overflow tank full? You could have an air bubble. Fill everything, start the jeep with the heat on low and let it get up to temp, then let it cool down and see if you need to add coolant. I don't think even a fully plugged heater core would do much other than give you no heat.
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Unread 04-01-2009, 05:27 PM   #6
Nburns24
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I just went out and started the car and it actually didn't overheat but I couldn't take it for a drive since I still have the bumper off. However, the heat is still not working but the input hose to the heater core was semi-warm. I'm hoping its just an air bubble, I don't know what else it could be at this point.
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Unread 04-01-2009, 06:47 PM   #7
walter_da_jpr
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My bet is a bubble, or a heater core that gets clogged intermittently. I say flush it way beyond what you think is appropriate, then fill it back up and run it while constantly refilling the radiator. Eventually it will be totally burped.

Oh, and are your fans working?
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Unread 04-01-2009, 07:18 PM   #8
baxy
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replace the radiator cap did you install the thermostat with the wax pellet into the engine ?
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Unread 04-01-2009, 08:27 PM   #9
Nburns24
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yea my fan works fine, the upper hose to the heater core is warm and the bottom is cold so I'm guessing my heater core is still blocked but when I flushed it I did so until the water was clear and coming through no problem on both ends....I'll check it out again tomorrow morning...
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Unread 04-01-2009, 09:14 PM   #10
Drenyce311
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burp all the air out. If your still getting air in system. I think you might have a cracked head!
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Unread 04-01-2009, 09:19 PM   #11
the88thpianoman
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Quote:
Originally Posted by Drenyce311 View Post
burp all the air out. If your still getting air in system. I think you might have a cracked head!
That is very possible, as the OP has a 2001.
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Unread 04-01-2009, 09:26 PM   #12
baxy
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identifix has alot of hit for loose impeller on water pump even on ones that were changed recently as well as a lot of hit for plugged radiators

I know you replaced these parts I'm just reporting what a search of identifix brought up
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Unread 04-01-2009, 09:47 PM   #13
Heap-O-Jeep
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my best suggestion is to double check your thermostat installation as stated by baxy replace the rad cap. then try this take off the top heater hose at the engine side and pour the coolant directly into the hose with the rad cap off and you can purge the air that way. or you can take off both hoses and pour coolant directly into the lower hose of the heater core at the engine side with the top hose off purging the air from the upper hose either way just try double and triple check making sure no air is in the system. next if your thermostat is in correctly and ther is no air in the system. check yoru electric cooling fan for proper operation. there is a cooling fan transistor that fails and the fan does not work. i would check this by idling the engine and watching the temp gauge go higher than normal it might take 15-30 minutes at idle for it to overheat. when its hot and gettign close to the red check to see if the fan is running. if not try replacing the transistor some parts guys call it the relay but its actually a transistor and it makes the fan work at a variable speed. its difficult to power up the fan with direct 12 volts because it wont just run directly hooked up to 12 volts. these are my suggestions. good luck!
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Unread 04-01-2009, 09:47 PM   #14
Drenyce311
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This happened to me in my brothers 92 eclipse gsx. He just got the head resurfaced with new valves, and cleaned. Then one day I took it for a spin and the top radiator hose busted while i was on the williamsburg bridge in NY and I pulled over when i got across the bridge. Once I turned around the car overheated and shut off. It only took that one overheat to warp the head. We did everything Nburns did Thermostat, waterpump, flush, burp the car and the system kept getting air in the system. We took off the head and it was warped. So what we decided to do was since I blew the motor I bought my brother another engine from an automatic and he just started swapping parts from one motor to another and just decided to upgrade the crankshaft, cams gears pistons, etc. So now he has a track car!! street legal!!

Moral to the story is he might have a warped head!
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Unread 04-01-2009, 09:52 PM   #15
baxy
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it's hard to get a good working cooling system to get to the fan on temp while sitting in the shop or driveway
I think it is somewhere around 225 degrees I could look for that spec if you need it
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