JK overheating then not

GeoWillys

GeoWillys

New member
I have a 2015 JK that over a period of a week started having the temp gage hitting the 3/4 mark when normal driving on a cool day. No engine lights or anything else but I have two 2015 JKs which I have owned since new and have never seen the gage go over 1/2 way. Dropped at dealer and they say they cannot duplicate the issue, everything checks good. Anyone had this issue.
 
Try replacing the thermostat and burp the system. I also had a radiator leak at the seam where the plastic and metal meet.
 
Yeah I think that is probably a good starting point. They wont change the thermostat because they did not get the thermostat discrepancy code or whatever, boneheads. I am going to do both JKs in one felled swoop. Thanks for the reply.
 
You can check thermostat operation yourself with a temp gun laser. Measure temps on both sides to make sure it's opening.

Also, next time it's acting up, make sure your fan is working.
 
JK overheating - 2013

Similar issues...

Bought my JKU new
4.88’s
37’s
4” Teraflex lift
Front and rear eLockers

Suddenly at 69k started to run hot. Now it overheats on long gradual climbs at ~3k RPM’s

Replaced: thermostat twice (196 and then a 180 degree), thermo housing, water pump, temp sensor, radiator cap (tried a new 16psi and a 18 psi), installed new aluminum radiator. Flushed twice and properly burped the cooling system each time

Drives fine until steady uphill moderate climb then overheats instantly. Today overheated and boiled over out of overflow tank driving to lunch.

Any suggestions from here are surely welcome!!!
 
I am fairly new to the JK platform (coming from having an XJ for the last 9 years). My XJ had a partially clogged radiator that had similar symptoms. It would idle fine, but when put under load it would run hot. After I installed a new radiator it ran great. Good Luck!!
 
sburt911z said:
Similar issues...

Bought my JKU new
4.88’s
37’s
4” Teraflex lift
Front and rear eLockers

Suddenly at 69k started to run hot. Now it overheats on long gradual climbs at ~3k RPM’s

Replaced: thermostat twice (196 and then a 180 degree), thermo housing, water pump, temp sensor, radiator cap (tried a new 16psi and a 18 psi), installed new aluminum radiator. Flushed twice and properly burped the cooling system each time

Drives fine until steady uphill moderate climb then overheats instantly. Today overheated and boiled over out of overflow tank driving to lunch.

Any suggestions from here are surely welcome!!!
Click to expand...

You prob still have air the system (heater core) post burping or a small leak somewhere allowing air in. I would suggest trying to burp it again first. If not then you could have a small clog in the radiator as posted above
 
Mine used to kind of do the same thing, but didn’t get hot enough to boil out anywhere. But it would get up there temperature wise driving up hills. I could never figure out why, I have a hood louver, vented wheel liners, etc and it would still get up to 250 up hills.

Part of the issue was I had a coolant leak but even when the coolant levels were full it would still overheat.

Long story short I put a mishimoto radiator in and I haven’t had an issue since. The Jeep doesn’t get hot going up hills anymore. I think the fact it holds 20-30% more coolant than a stock radiator helps.

Hope you figure it out soon, I know how frustrating it is.


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Mines doing the same thing. It’ll go up to about the 3/4 mark on the gauge then go back down once the fan kicks on. Gonna try washing the radiator out to see if there’s any mud or anything gummed up there and go from there.


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longarmwj said:
Mines doing the same thing. It’ll go up to about the 3/4 mark on the gauge then go back down once the fan kicks on. Gonna try washing the radiator out to see if there’s any mud or anything gummed up there and go from there.


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Click to expand...

This is a big issue. Most of the time it’s old mud stuck between the condenser and the radiator not allowing proper air flow to pull the heat out of the coolant. I’m sure you will be surprised as how much washes out.
 
I've been dealing with the same issue on my 2010. When running the AC and at 65mph, temperature would climb to the 3/4 mark until I turned the AC off and slowed down...temp would drop back to midpoint.

I had the AC compressor checked and even though the AC was blowing cold, it was low. They put dye in the system and haven't had issues since getting the AC done but I still need to take it back to check for leaks.

I suspect my water pump may be failing as well.

I replaced the thermostat and housing at a hotel parking lot due to a pinhole in the housing but when I refilled the radiator it appeared to not have a constant flow.
 
I’ll just throw this out there, try “burping” it uphill with the radiator cap off. It’s an old trick on atv’s that works but I’ve never burped a coolant system without the radiator standing tall without success. Cozdudes right about the air problem.
If it persists it may be a leak, check your therm gasket or maybe head gasket ☹️


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There’s a bleeder screw on the thermostat housing on the 3.6. You have to remove the throttle body in order to get at the screw. Open the bleeder and remove the cap, when you get coolant flowing from the bleeder, close it up and top off the radiator.


Typed by my very own fat fingers on my iPad or iPhone.
 
I had the same issue. I replaced the fuse, thermostat, and flushed the radiator. Then it overheated again. I found the negative battery terminal was slightly loose, not even enough to move it by hand. Tightened it up and haven't had any issues since. The terminal was loose enough to prevent the fan from turning on.
 
Us old mechanics jack up front of vehicle about a foot, so rad cap is highest point of system. Run until cooling fan kicks in. Put cap on after topping up before letting front end down.


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Mine does the same as do plenty of JK's I know, the temp will only rise on a uphill but only to between 1/2 and 3/4 never goes further.

Had all the tests done and all in order. Seeing other JK 3.6's do it as well I learned to live with it.

PS. It never overheats, no light come on and no boiling.
 
I am having same issue with my 2012 where it gets hot going up hills. Changed thermostat with a Mishimoto it stopped for a little while then it overheated when my wife was driving she stopped driving it when it hit 250 and had towed home for free. I Chan the water pump and thermostat again it was opening. Now it gets to 245 uphill. Not sure if I should change the radiator or is it something simple. Maybe I have a leak I smell coolant


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