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Unread 01-14-2012, 01:34 PM   #1
MrKevinRosales
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1996 XJ Cherokee 
 
Join Date: Dec 2011
Location: Willimantic, CT
Posts: 32
98 ZJ overheating

I changed the radiator in my aunts 98 ZJ and everything seemed fine, i made sure to leave everything the way it was, I flushed the system too and added all new 50/50 coolant

but now it is overheating very quickly. Also when i turn the heat on the check gauges light flashes.
I thnk it might be the thermostat thought i'm not entirely sure.
any suggestions?
Also how would i go about changing the thermostat?

thanks

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Unread 01-14-2012, 02:29 PM   #2
xxmikewalshxx
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1997 ZJ 
 
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Location: Plains, PA
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Thrmo is cheap and easy, on the 5.2 its right behind the alt. Follow the big hose to it. That might be the problem.
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Unread 01-14-2012, 03:33 PM   #3
MrKevinRosales
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OK thanks, This is for a 4.0 what temperature thermostat would you recommend?
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Unread 01-14-2012, 03:45 PM   #4
xxmikewalshxx
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Not sure they will give you the option but it's cold out, go high temp.
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Unread 01-14-2012, 04:11 PM   #5
sebian
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1995 ZJ 
 
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195 degree is the oem spec t-stat. If I remember correctly, on the 4.0 it is more or less on the front of the block. Have a big bucket handy to catch all the fresh coolant you just dumped in there, and reuse it.
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Unread 01-14-2012, 04:34 PM   #6
SJZ
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1998 ZJ 
 
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Quote:
Originally Posted by MrKevinRosales View Post
I changed the radiator in my aunts 98 ZJ and everything seemed fine, i made sure to leave everything the way it was, I flushed the system too and added all new 50/50 coolant

but now it is overheating very quickly. Also when i turn the heat on the check gauges light flashes.
I thnk it might be the thermostat thought i'm not entirely sure.
any suggestions?
Also how would i go about changing the thermostat?

thanks
Before you change the thermostat, are you sure it's full of coolant? You can't just fill to the top of a cold radiator, put the cap on, and walk away. You should leave the cap off, let the engine run, and monitor the coolant level at the radiator neck. As the engine heats up, and the thermostat opens, you will see the level go down, at which time you add more until full.
It is possible that you dislodged some debris which is clogging the thermostat, but I think that's unlikely, unless the old coolant was a real mess. If the upper hose is getting hot, the thermostat is probably OK.
Are you sure that the air flow thru the radiator is unimpeded. I'm assuming the water pump is turning properly.
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"Those who hammer their guns into plows, will plow for those who do not." -Thomas Jefferson
___________________________________________
'98 ZJ Laredo 5.2 Selec-Trac (249 to 242 swap)
'05 KJ Limited 3.7 Selec-Trac
'94 ZJ Limited 5.2 Q-Trac- sold, after 17 years
'67 International Harvester Scout 800; 345ci V8,T18 4spd, Dana 20 TC
'06 Chrysler 300C SRT8 6.1L
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Unread 01-14-2012, 05:12 PM   #7
MrKevinRosales
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1996 XJ Cherokee 
 
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Location: Willimantic, CT
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I ran the engine for a while after i filled the radiator and checked the level again and it seemed to have stabilized. prior to that the while i was filling the radiator i would pour some in and it would seem to be full but shortly after it would bubble and settle down so then i would pour more into it.
I did this until it didn't do that any more.

I don't think that the old coolant was too bad, but, the resevoir was pretty dirty which is why I decided to change out all the coolant.
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Unread 01-14-2012, 05:56 PM   #8
gunner44
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1997 ZJ 
 
Join Date: Aug 2011
Location: Petoskey, Michigan
Posts: 641
I have a 97 but that Jeep, 98ZJ, has a coolant reservoir doesn't it, right rear corner of engine, there is a full and Add mark on it. "The level in the reservoir varies with the temp of the engine. When engine is cold the level should be slightly above ADD mark on the reservoir. Once the engine has wormed up , the level should be at the near he FULL mark. If it isn't allow the engine to cool then remove the cap form the (reservoir) and add 50/50 antifreeze." Haynes Book. Changing the radiator would not have damaged the thermostat, though check it for something blocking it. Check the wires to the temp sensor, you could have damaged it. Does that Jeep have a electric fan?
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Unread 01-14-2012, 06:45 PM   #9
SJZ
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Quote:
Originally Posted by MrKevinRosales
" when i turn the heat on the check gauges light flashes."
When you check the gauges, which ones are abnormal. From what you say, I'm assuming you mean that the check gauges light comes on as soon as you turn up the heat. Something as instant as that sounds electrical. If the belt is slipping, or even off a pulley, you may get a low voltage when you turn up the blower motor. Again, make sure your belt is correct, and that the water pump, fan, and alternator are spinning correctly. Maybe you knocked the belt off, or contaminated it with antifreeze while working. I have a V8, so I'm unaware, but as another poster asked, do you have an electric cooling fan? Is it working? Is that upper hose getting hot?
__________________
-Steve
"Those who hammer their guns into plows, will plow for those who do not." -Thomas Jefferson
___________________________________________
'98 ZJ Laredo 5.2 Selec-Trac (249 to 242 swap)
'05 KJ Limited 3.7 Selec-Trac
'94 ZJ Limited 5.2 Q-Trac- sold, after 17 years
'67 International Harvester Scout 800; 345ci V8,T18 4spd, Dana 20 TC
'06 Chrysler 300C SRT8 6.1L
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