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Unread 09-02-2010, 10:24 PM   #1
CrusherCurtis
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Overheating help!!!!!!!!!

Just bought a 99 4.0. Its overheating.

Here we go.

When it first overheated the coolant was boiling in the cooling system and coming out the reservoir. It was really a thick brown paste. Time for a flush. What I first did was drain the radiator (the coolant was very thick and brown). I then pulled the thermostat, which was completely broken into pieces under the housing. I replaced the housing with no thermostat and poured in a bottle of radiator flush and water. I let the car idle until 210 was reached and then I revved it up a down a few times. The needle remained in the middle. I turned it off and thought I had solved my problem (broken thermostat) and let it idle again about 5 hours later. After normal operating temp was reached. I then held the idle at about 3000 revs, until the needle moved slightly to the right of the 210. I immediately let go of the throttle and continued to let it idle, then all of a sudden the check gauges light flashed and the the needle jumped to the far right. I turned it off and checked under the hood and here we go again. Brown water shooting out of my reservoir (though thin this time). So today I ran water through cooling system initially with my garden hose. The water coming out was a healthy rust brown but eventually it began to clear up. I also installed a new thermostat and added more radiator flush to the water. I haven't tried to run it yet will be doing that tomorrow.


The original owner hasn't touched the cooling system and they bought it new. So everything is original which would explain why the thermostat was in pieces.

What could be wrong with cooling system? Should I continue to flush or assume its the radiator? Also is the electric fan for the A/C condenser or is it actually an engine cooling fan? If its a cooling fan then I've found my problem b/c that sob sat idly by while my I Jeep overheated.

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Unread 09-02-2010, 10:52 PM   #2
robsjeepxj
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Take it back!!! The heads most likely cracked and if they drove it like that which it sounds like they did then the rod and crank bearings are probably shot too. You can try putting on a new head but that may or may not do it. Try searching the forum here you'll find lots of threads about overheating and cracked heads. If it's not caught right away then it will destroy the motor. The brown thick paste is motor oil mixed with the coolant. If it was that poorly maintained then you are in for a lot more headaches down the road.
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Unread 09-02-2010, 10:58 PM   #3
CrusherCurtis
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There is no coolant in the oil and it still runs great and is very strong. Also I coundn't take if back if I wanted. Also oil change is past due and its not low on oil at all and brown is more of a rust color rather than black.
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Unread 09-02-2010, 10:59 PM   #4
0okamiDigital
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I remember seeing a thread about this same stuff a while back... lemme do some digging. -- brb-

http://www.jeepforum.com/forum/f9/ov...brown-1091818/

Does it look like this?
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Unread 09-02-2010, 11:33 PM   #5
robsjeepxj
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I guess run a flush solution through the cooling system and see how it does. Checking that fans are in fact working, the radiator cap is good, and system is circulating fluid well (radiator isn't clogged, water pump is working etc.) would be next on my list. I would go a compression test on all the cylinders and a leak down test on the cooling system as well just to be sure your not just wasting your time though. Good luck with it.
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Unread 09-03-2010, 12:00 AM   #6
CrusherCurtis
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Is the electric fan for the condenser or does it actually cool the engine. Also how do I do a leak down test.
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Unread 09-03-2010, 12:20 AM   #7
robsjeepxj
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I guess both but it helps cool the engine too even without the a/c on if it gets above 220* (approx). Leak down test is done by putting a hand pump on the radiator and seeing if the pressure holds or drops off. It's used to help find leaks but can be used for this too. Mechanical fan should not spin more than 1 turn by hand (less when it's hot) or it's no good either, check for play too.
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Unread 09-03-2010, 12:22 AM   #8
iraqsucks
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the electric fan is for the ac condenser but it comes on once it reaches a certain temp. if everything is right.
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Unread 09-03-2010, 12:23 AM   #9
CrusherCurtis
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Well my fan definitely didn't cut on with the gauge reached 220. However it did cut on when I turned the A/C on. Is this likely a sensor issue?
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Unread 09-03-2010, 12:29 AM   #10
robsjeepxj
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Possibly. If you unplug the sensor and the fan comes on it's most likely the sensor. There are a couple fuses and relays that control the E fan as well as the sensor. I do remember reading a thread on it recently. You can search for it or find yourself a FSM on the web it will have all that info. Check all your fuses too, under the dash and under the hood. It shouldn't be getting up over 220* in the first place though so don't get sidetracked too much with the E fan thing you have other more primary issues to deal with first.
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Unread 09-03-2010, 12:32 AM   #11
CrusherCurtis
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Also any cheap way to do a drip down test? When I first got the Jeep I looked into in and my local parts store wanted $200 for the kit.

Is the mechanical fan suppose to be enough to get the engine cool or is the E fan necessary?
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Unread 09-03-2010, 12:34 AM   #12
iraqsucks
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mechanical fan should be enough. is your mechanical fan shroud broken?
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Unread 09-03-2010, 03:50 AM   #13
sAe23
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X2 on the radiator cap...
And a reverse flush too.
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Unread 09-03-2010, 07:34 AM   #14
303_XJ
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Sounds like you have a bad fan clutch. With the motor turned off, spin the fan blades with your hand. Is there any resistance?
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Unread 09-03-2010, 07:52 AM   #15
Sailor553
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While flushing - make sure you "open" the heater valve/switch.
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