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post #1 of 57 Old 11-25-2015, 02:07 PM Thread Starter
Scott1994
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1994 YJ Wrangler 
 
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Running hot

My 94 4.0 is now/still running hot. I have changed the following, temp sensor, temp sending unit, water pump, thermostat, and coolant. The temp goes to just about redline the cools back down to 210, the goes back to redline then back down; I think you get the picture. I have a fan shroud and the splash guard underneath. Maybe my gauge is reading wrong, anyone. Have that issue before?

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post #2 of 57 Old 11-25-2015, 03:23 PM
Drednot
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How long has it been doing this? Before or after parts change?
How long ago did you change those part?
Did you change those parts all at the same time? One thing after the other chasing this overheat?
What driving conditions cause this fluctuation. Freeway only? Stop and go/idling only? All the time as soon as it warms up?
Does running the heater change it any?

91 YJ Sahara, 4.0L, AX-15/NP231, D30/D35@3.07
12 Cherokee 4x4,3.7L,42RLE/MP1522, D30M/8.25@3.73
Emission test=YES
"Non Vi Sed, Arte"
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post #3 of 57 Old 11-25-2015, 05:29 PM Thread Starter
Scott1994
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Drednot, I give you credit for reading my post with the title. So I bought the jeep a little over 7 months ago, I don't drive it that much, only weekends if that. It has never had a heater core installed since I bought it an still doesn't, both coolant lines are currently capped at the engine. I have never had it on the highway, it is usually around town. Florida is hot and a ton of blue hairs on the road so it is slow driving. I started with the thermostat and temp sensor, that did nothing for cooling; helped run better though. Then I just did my RMS and while apart I changed the timing chain, and while there I changed the water pump, and while the water pump was off I changed the fan clutch. Since none of that worked I changed the temp sender. All to no avail. The coolant line from the radiator to the engine on top just doesn't seem to be really hot, but I don't want to overheat the engine.
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post #4 of 57 Old 11-25-2015, 05:35 PM
RockWoRM
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How old is your radiator? Factory? If so, could be all plugged up. Mine was (many moons ago) Replaced with 3 row all metal rad. No more over heats in Cali. 110* summers and winch blocking air.

'05 LJR, 6sp, RC long arm w/MC 6" coils, 5.13 D44's w/chromo shafts, MetalCloak fenders/sliders/body armor, 37x12.50 MTR's, Warn 9.5, RockHard swing out w/full spare. <><
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post #5 of 57 Old 11-25-2015, 05:46 PM Thread Starter
Scott1994
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Don't have a clue how old the radiator is. I was afraid someone would suggest that. If I do change the radiator what would others recommend. Stock, aluminum, two or three core?
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post #6 of 57 Old 11-25-2015, 07:44 PM
Drednot
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Stock is fine. It works for all climates and only needs an upgrade when you go to v8. it would be a wise investment to throw a heater core in while its apart and I advise to use a mopar 195 thermostat and radiator cap.

I have A/C and a winch in front of my NAPA radiator and it functions flawlessly at 115 degrees in Phoenix traffic, idling out in the desert, or at 80 MPH.





91 YJ Sahara, 4.0L, AX-15/NP231, D30/D35@3.07
12 Cherokee 4x4,3.7L,42RLE/MP1522, D30M/8.25@3.73
Emission test=YES
"Non Vi Sed, Arte"
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post #7 of 57 Old 11-25-2015, 07:59 PM
89YJBuilder
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I would say have it power flushed. It could be a plug in the radiator passages or in a water jacket in the engine block or head.

Keep your boogger hook off the bang button!
When all else fails... ham radio is there!
KG6YSF
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post #8 of 57 Old 11-25-2015, 09:28 PM
ShiJon
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Did you make sure to get the T-stat in right-side-up (pin hole) and get all the air out? It sound like it may be air locked.
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post #9 of 57 Old 11-26-2015, 06:54 AM
RockWoRM
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Quote:
Originally Posted by Drednot View Post
Stock is fine. It works for all climates and only needs an upgrade when you go to v8.
I agree to a degree. (pun intended)
A stock all metal 2 row will perform as stated. But I had problems pulling long steep hills in summer without getting hot. Not over heated, but it would rise. Along with our wonderful floor boards burning our feet, me thought that a bit much.
IMHO, the 3 row is the same direct bolt in size and only a few bucks more... so my thinking is if you have the winch, AC etc., then why not?

'05 LJR, 6sp, RC long arm w/MC 6" coils, 5.13 D44's w/chromo shafts, MetalCloak fenders/sliders/body armor, 37x12.50 MTR's, Warn 9.5, RockHard swing out w/full spare. <><
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post #10 of 57 Old 11-27-2015, 08:41 AM Thread Starter
Scott1994
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So I jacked up the right side of the jeep, that created room for more coolant. I filled it up and let it run with the cap off, the fluid never went down, it just started to overflow. New thermostat bad? Engine clogged?
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post #11 of 57 Old 11-27-2015, 11:48 AM
Drednot
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If you want to make sure there are no clogs in the engine, you need to take off the water pump and thermostat and you can blast out anything in it easily with a garden hose at that point.






91 YJ Sahara, 4.0L, AX-15/NP231, D30/D35@3.07
12 Cherokee 4x4,3.7L,42RLE/MP1522, D30M/8.25@3.73
Emission test=YES
"Non Vi Sed, Arte"
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post #12 of 57 Old 11-27-2015, 12:16 PM
89YJBuilder
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Quote:
Originally Posted by Scott1994 View Post
So I jacked up the right side of the jeep, that created room for more coolant. I filled it up and let it run with the cap off, the fluid never went down, it just started to overflow. New thermostat bad? Engine clogged?
Putting more fluid in will not help. As you learned when the fluid gets hot, as with all things, it expands. That is why there is a "Full" mark on the reservoir and why it overflowed. The parts are more than likely fine. The idea to check and see if the thermostat is in correctly is about the best "easy" to do diagnostic step.

Keep your boogger hook off the bang button!
When all else fails... ham radio is there!
KG6YSF
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post #13 of 57 Old 11-27-2015, 03:11 PM Thread Starter
Scott1994
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So I pulled the thermostat and took it for a quick ride. It was a quick ride, but it stayed below 210. I really didn't want to believe the new thermostat was bad. I guess while it is out I will run some cleaner through the system and change the fluid and get a new OEM thermostat.
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post #14 of 57 Old 11-27-2015, 03:18 PM
cgcarpenter
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Quote:
Originally Posted by Scott1994
So I pulled the thermostat and took it for a quick ride. It was a quick ride, but it stayed below 210. I really didn't want to believe the new thermostat was bad. I guess while it is out I will run some cleaner through the system and change the fluid and get a new OEM thermostat.
I had a similar problem with a fail safe thermostat on a friends jeep. The Tstat was sticking until it would reach ~235 and then it would drop to operating temp and back up. Replaced the stat with a mopar one and problem solved
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post #15 of 57 Old 11-30-2015, 01:34 PM
89YJBuilder
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You can test them before installation by dipping then into a pot of boiling water. You will see how it opens, if it is at all sticking or opening jerky take it back. Trick learned in High School auto shop class.

Keep your boogger hook off the bang button!
When all else fails... ham radio is there!
KG6YSF
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