Running Hotter and Losing Coolant

[Chadnutz]

First noticed an issue last week. I got home and putted down a long gravel driveway. Got out to do something. Left the Jeep running with A/C on so radiator fan was running. When I got back to Jeep, fan was on full jet engine mode. I got in and slider gauge was normal. Digital gauge read 230°F but falling fast. That was odd.

Next day driving to the coast and I noticed it was running warm just going down the highway. Around 215°F. I got stopped in traffic and it crept up to 243°F. I was expecting it to drop quickly like it did at home but it didn't. I pulled over and did about 5 full blast heater start/stop cycles to get it to 210°F. Then I removed the cap and added about a 1/3 gallon of water. Started it up and it stayed much cooler at idle and for the rest of the drive. I added water once more after a stop to eat.

When I got back home I checked the level when cold and added a little bit more water. In total I have probably added 2/3 gallon. I've checked the level two mornings in a row and I'm fairly confident I am losing coolant, but all hoses are dry. There is a residue on the EGR cooler outside of it, on the O2 sensor, and there is a wet connector below that. I can't tell if the residue is oil or coolant. I bought a pressure test kit that just arrived this morning so I will check it Saturday morning when it's cool.

The odd thing is that it is running hot sometimes.... When I just pulled in to work I stopped at the gate to badge in. By the time I parked coolant was 219°F. Either the thermostat is randomly restricting flow, or something else is randomly putting more heat into the system. This is a cool morning relative to other times I'm driving lately. I don't understand why the temperature would be fluctuating so much. I don't generally watch the digital gauge, but in all of my 6 years of owning it I have never heard the fan run like it did twice last week. I also learned that the slider gauge is at the normal location between 128-243°F.

I don't really think I can smell coolant. I have one slight residue on the garage floor under the EGR cooler. Again, I can't tell if it is coolant or oil because it is so slight. Cap is holding pressure.

Pictures attached.

Any ideas?

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[Bandit’s Lair]

And you checked the coolant reservoir? They’re notorious for cracking along the bottom fitting. Not sure on the age of the vehicle but other things to check if it isn’t obvious, squeeze your coolant tubes when it’s cool. Too squishy or if you see evidence of dry rot/damage and those need replaced. I see you’re in TX so heat is an issue.

 

[Chadnutz]

And you checked the coolant reservoir? They’re notorious for cracking along the bottom fitting. Not sure on the age of the vehicle but other things to check if it isn’t obvious, squeeze your coolant tubes when it’s cool. Too squishy or if you see evidence of dry rot/damage and those need replaced. I see you’re in TX so heat is an issue.

I just checked all around the reservoir with a dry paper tower and found no liquid. I would expect a reservoir leak to be large enough to see, but it was worth checking anyway.

 

[Dave D]

Thermostat bad, normally a cheap place to start.

 

[Chadnutz]

Thermostat bad, normally a cheap place to start.

I had a chat with AI last night and we came to the same conclusion. It is erratic and happens mostly at idle where there wouldnt be much pressure behind it or flow from pump. The water pump should either work or not.

 

[dirtdevil]

First noticed an issue last week. I got home and putted down a long gravel driveway. Got out to do something. Left the Jeep running with A/C on so radiator fan was running. When I got back to Jeep, fan was on full jet engine mode. I got in and slider gauge was normal. Digital gauge read 230°F but falling fast. That was odd.

Next day driving to the coast and I noticed it was running warm just going down the highway. Around 215°F. I got stopped in traffic and it crept up to 243°F. I was expecting it to drop quickly like it did at home but it didn't. I pulled over and did about 5 full blast heater start/stop cycles to get it to 210°F. Then I removed the cap and added about a 1/3 gallon of water. Started it up and it stayed much cooler at idle and for the rest of the drive. I added water once more after a stop to eat.

When I got back home I checked the level when cold and added a little bit more water. In total I have probably added 2/3 gallon. I've checked the level two mornings in a row and I'm fairly confident I am losing coolant, but all hoses are dry. There is a residue on the EGR cooler outside of it, on the O2 sensor, and there is a wet connector below that. I can't tell if the residue is oil or coolant. I bought a pressure test kit that just arrived this morning so I will check it Saturday morning when it's cool.

The odd thing is that it is running hot sometimes.... When I just pulled in to work I stopped at the gate to badge in. By the time I parked coolant was 219°F. Either the thermostat is randomly restricting flow, or something else is randomly putting more heat into the system. This is a cool morning relative to other times I'm driving lately. I don't understand why the temperature would be fluctuating so much. I don't generally watch the digital gauge, but in all of my 6 years of owning it I have never heard the fan run like it did twice last week. I also learned that the slider gauge is at the normal location between 128-243°F.

I don't really think I can smell coolant. I have one slight residue on the garage floor under the EGR cooler. Again, I can't tell if it is coolant or oil because it is so slight. Cap is holding pressure.

Pictures attached.

Any ideas?

So like many have probably already said, check the bottle for leaks. Yesterday I got a sweet sent which made me look. I can feel the wet and slick drips of antifreeze all the way around the seam of the bottle. This has been a known issue with jeep for many years now. I have a 2023 JT/R so you’d think that a long standing issue like this would have been fixed by now.. yeah not so much.

 

[Chadnutz]

I have checked the bottle thoroughly.
Coolant level in reservoir drops around 1-2 mm/day.

• Oil level is good and residue on dipstick looks normal.
• Oil cap looks good. No sludge.
• No visible leaks around head gasket where I can see.
• No black in expansion tank.
• No coolant leaks anywhere.
• No white smoke.
• No sweet exhaust smell.
• No liquid in EGR cooler.
• EGR pipe to EGR valve all dry soot.
• Runs great.

The only leaks I can find are slow oil leaks.

My coolant pressure test kit does not have a cap that matches this expansion tank cap. I need to find out how Jeep runs a coolant pressure test.

 

[Jeepmonster]

I had a slow leak. UV light showed leak around the bottom of the coolant reservoir and coolant that had sprayed and dripped onto rhe EGR cooler. Turned out to be a small crack that would only leak (only slightly) under pressure.

Crack from the inside.

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