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Discussion Starter · #1 ·
I have a 2015 GC Overland Diesel with 94000km on it.

After driving around town today at speeds of about 30-40km/h I arrived at my destination and shut off off the engine. I then heard a rumble from the front of the car sounding like water boiling. Sure enough it was the coolant boiling in the expansion bottle. The temp was normal the entire trip. Normal being between quarter and halfway mark.

I went about my business and on the way home, kept an eye on the temperature. All appeared just fine. On arriving at home, I left the Jeep to idle and watched the temp gauge rise ever so slowly but never passing the halfway mark, this said the coolant started pushing out the overflow and eventually started to boil. The radiator fan was standing completely still. Turning on the AC, the radiator fan immediately powered on, cooled the radiator and the coolant stopped boiling over. As the coolant contracted, I could see that the level was now too low so I topped it up and tested once again. Same thing happened. It takes a very long time i.e. 10 -15 minutes or so, before the coolant starts to push out the overflow but it happens eventually.

Thinking back, I got the smell of antifreeze from time to time but since I generally drive with the AC on, the condition rarely surfaced. This makes me think the problem has been around since buying the Jeep in 2018.

What I have established so far:
With the AC turned off, when at idle for extended times or very slow driving, the coolant expands to the point where it starts pushing out the overflow.
When this happens the radiator fan is not turning at all.
The coolant eventually starts to boil although the temperature gauge is on or just below the halfway mark. Normal, as I know it, is being just above quarter.
Driving on the freeway, this does not happen. Turning on the AC, starts up the radiator fan and the temps are normal even at idle or in traffic.
This model has no fan relays or fuse located in the fuse box. The spaces where they should be located on the gas models are not in use.
The fan is not faulty because it spins when using the AC and at the same time the coolant situation normalizes.
With the AC off, the radiator fan never turns on. I have not seen it on except for when the AC is on.
I cannot find a relay but I have read somewhere that the fan speed is controlled by the ECU.

The Jeep is out of warranty but still serviced by Jeep. I am however concerned to take the car to them with this problem. I dont want them to start stripping fans and coming with long sad stories. My Jeep is pristine and I just don't want it butchered.

Has anybody had this issue? Could it be the temp sensor reading too low? My best guess is that the coolant temp sensor provides signal to the ECU that in turn, switches on the fan. A low reading would allow the coolant to boil over since the ac fan would never start. I have never seen the temperature sensor in the red. This is my best guess at the moment.

Im also thinking radiator cap. Its hard to believe that it could be faulty. It looks fine?

Anybody ever had this same issue or have any thoughts?
 

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I have a 2015 GC Overland Diesel with 94000km on it.

After driving around town today at speeds of about 30-40km/h I arrived at my destination and shut off off the engine. I then heard a rumble from the front of the car sounding like water boiling. Sure enough it was the coolant boiling in the expansion bottle. The temp was normal the entire trip. Normal being between quarter and halfway mark.

I went about my business and on the way home, kept an eye on the temperature. All appeared just fine. On arriving at home, I left the Jeep to idle and watched the temp gauge rise ever so slowly but never passing the halfway mark, this said the coolant started pushing out the overflow and eventually started to boil. The radiator fan was standing completely still. Turning on the AC, the radiator fan immediately powered on, cooled the radiator and the coolant stopped boiling over. As the coolant contracted, I could see that the level was now too low so I topped it up and tested once again. Same thing happened. It takes a very long time i.e. 10 -15 minutes or so, before the coolant starts to push out the overflow but it happens eventually.

Thinking back, I got the smell of antifreeze from time to time but since I generally drive with the AC on, the condition rarely surfaced. This makes me think the problem has been around since buying the Jeep in 2018.

What I have established so far:
With the AC turned off, when at idle for extended times or very slow driving, the coolant expands to the point where it starts pushing out the overflow.
When this happens the radiator fan is not turning at all.
The coolant eventually starts to boil although the temperature gauge is on or just below the halfway mark. Normal, as I know it, is being just above quarter.
Driving on the freeway, this does not happen. Turning on the AC, starts up the radiator fan and the temps are normal even at idle or in traffic.
This model has no fan relays or fuse located in the fuse box. The spaces where they should be located on the gas models are not in use.
The fan is not faulty because it spins when using the AC and at the same time the coolant situation normalizes.
With the AC off, the radiator fan never turns on. I have not seen it on except for when the AC is on.
I cannot find a relay but I have read somewhere that the fan speed is controlled by the ECU.

The Jeep is out of warranty but still serviced by Jeep. I am however concerned to take the car to them with this problem. I dont want them to start stripping fans and coming with long sad stories. My Jeep is pristine and I just don't want it butchered.

Has anybody had this issue? Could it be the temp sensor reading too low? My best guess is that the coolant temp sensor provides signal to the ECU that in turn, switches on the fan. A low reading would allow the coolant to boil over since the ac fan would never start. I have never seen the temperature sensor in the red. This is my best guess at the moment.

Im also thinking radiator cap. Its hard to believe that it could be faulty. It looks fine?

Anybody ever had this same issue or have any thoughts?
Hi, I am having the same problem. Could you ever elaborate with how the fan would not run but the problem was with the cap? having the same problem.
Thanks,
Rob
Be CAREFUL GUYS.......I just spent $17500 for a new engine. Driving on Interstate thru North Carolina my check eng light came on, I looked at all guages and all were OK. I got off at next exit,..stopped at "red light" and ENG OIL TEMP message popped up. I turned the engine off to let things cool. It would never restart NOR TURN OVER. Called tow truck to nearest Jeep dealer. ENGINE SIEZED!!! If the coolant is LOW it will NOT READ high on your guage cause there is no water to cause the sensor to measure temp. The ONLY SAFE READING is the OIL TEMP selection on your "info computer" (where you check your DEF and tire pressure) If the OIl TEMP gets near redline you are close to engine seizure and lots of $$$$. I did have the engine replaced because the car is like new and Jeep has had the amazing foresight to drop the diesel in GC's. (stupid) They now offer it in the Wrangler??? Haven't figured that out:rolleyes:
 

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Discussion Starter · #5 ·
Hi, I am having the same problem. Could you ever elaborate with how the fan would not run but the problem was with the cap? having the same problem.
Thanks,
Rob
I havent been on the forum for a while. Sorry for this very late reply. I was unaware of it. To answer the question and add on to it, the system was not holding pressure. The radiator cap was bad and the coolant would eventually boil since it exceeds the boiling temp. Before changing the cap, the fan did come on, but that was after the coolant already started pushing out of the reservoir. This is what initially caught my attention. I thought it was boiling due to the fan turning on too late but actually it was simply boiling due to the cooling system not being pressurised. The fan comes on at about 106C which I believe is correct.

Today, close to two years later and only 20 000km down the road, the new radiator cap I bought from JEEP, Original Part, is bad once again. The cooling system is clean, original and using the JEEP coolant. System is not holding pressure at all with the cap fully secured. The little degas pipe has coolant in it, confirming its pushing past the cap. At running temp there is not much pressure in the radiator hoses. As a result the temp fluctuates between 89C and 116C. I was towing about 2.5 tons on the weekend and the car reached 116C towing at 100km/h and I was really nursing it along to avoid problems. I was keeping a very close eye on it and all is good until you turn off the vehicle, thats when the coolant starts to boil over I suppose due to hot pockets developing in the block as the heat dissipates due to the water pump not turning.

Considering I am changing more radiator caps on this jeep alone, than I have replaced between all my other vehicles I have ever owned combined, I am wondering if there is an issue with these specific radiator caps in general and whether many others have the same issues. I would think that driving for extended periods with a bad cap will eventually have severe consequences.

The temperature is far more stable when the system is under pressure as it should be. As would be expected.

As a note, yes the reservoir/expansion bottle seat, where the cap mates to create a seal is perfect. There are no deformations or anything.

I hope that this helps others struggling with similar issues.
 

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Discussion Starter · #6 ·
New cap on and problem solved again. I asked the guy at the Jeep parts counter if they sell many of these and he said no, not at all.
I can say that if you drive with the AC on, you could possibly never even notice you have a problem unless you start towing. I m convinced this is the cause for many complaints of overheating whilst towing.
 
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