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Discussion Starter · #1 ·
I have a 2014 Jeep Grand Cherokee Summit with the 3.0L EcoDiesel and I've been struggling to resolve an overheating issue for the past few months. It's virtually undriveable and you have to drive it extremely gentle as to not make it overheat. I am mechanically inclined and do all of my own maintenance, and this has all begun when a dealership released the vehicle back to me with the expansion tank cap removed, which immediately overheated 10 minutes after picking up the vehicle. I've had nothing but problems since then.

The issue can be repeatedly duplicated and the engine will begin to overheat if there's any sort of load (climbing a decent grade on the freeway or surface streets, WOT, etc). If you back off and slow down, the temperatures will decrease and you can prevent it from overheating. Running at 75 mph on a flat freeway, the oil temps are steadily around 221 degrees and the coolant gauge needle is a bit elevated. To compare, the oil used to run around 205 degrees while cruising on the freeway. If you continue to push it just a little (even WOT while going downhill), the coolant temperature increases, oil temperature increases to over 232 degrees and then it will reach the "point of no return" and immediately overheat (coolant will increase its temperature to maximum, oil temperatures will increase to 270+ degrees if you attempt further driving, etc).

When driving it (and not overheating), I can turn on the heater and it will blow extremely hot air. When it's fully overheating (coolant temperature gauge is maxed out, and about 235 F according to AlfaOBD), I can turn on the heater inside the vehicle and there is NO HEAT! Additionally, the air coming off of the radiator at this time feels extremely cool, as if the radiator isn't even hot.

I have replaced the thermostat, and have duplicated the issue with the thermostat removed from the housing. After this, I discovered that the water pump was leaking, so I have also replaced the water pump with a brand new OEM Mopar water pump and all accompanying seals/o-rings. Concerned that there was a blockage in the radiator or heater core, I reverse flushed the radiator, heater core and engine, and then drove around for a few days with a chemical cleaner. After this, I reverse flushed everything again, used a professional strong chemical cleaner, reverse flushed again and then refilled with Mopar 68163848AB coolant mixed down to 50/50. Vacuum fill tool confirms that there are no leaks present in the cooling system. The EGR cooler was replaced under its recall warranty about 3,000 miles ago. Wondering if it was a warped head due to past overheating, I attempted to check for combustion leaks using the UView Combustion Leak Tester, but there are no combustion gasses present in the expansion tank.

Does anyone have any ideas why this could be happening? Thanks so much for any insight!
 

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Discussion Starter · #4 ·
Unfortunately, it's not just an air pocket. It was drained and refilled 5 times now, each time with a vacuum fill tool to ensure that it gets filled with no air. Additionally, the water pump is brand new as referenced in my first post. Thanks for your help! 🙂
 

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2015 Outdoorsman EcoD CC w/6.4' 4X4
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I'd your heater core does not have any heat, I wonder if there's a problem with the 3-way valve that directs coolant to the transmission TMU if there is no demand for heat in the cab from the HVAC system. I doubt that valve would cause the overheat issue.
 

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Discussion Starter · #6 ·
I don't believe that the 3-way valve exists on the Jeep Grand Cherokee platform. I can't find the valve on my vehicle, I can't find any applicable part numbers for my Jeep and the cooling system diagram for the Jeep doesn't show a 3-way valve anywhere.
 

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There is screw near the thermostat housing that can be used to take air out of the cooling system. Your symptoms calls for air lock in cooling system.
 

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Discussion Starter · #9 ·
New OEM Mopar water pump came with a new coolant temp sensor pre-installed. Also, when it's overheating, it's actually overheating - coolant is fully expanded in the expansion tank, and overflowing out of the overflow tube.
 

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If your radiator is cool when this thing is overheating then coolant is not circulating. When it's overheating, is the fan running?
 

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I don't believe that the 3-way valve exists on the Jeep Grand Cherokee platform.
It's a very good possibility it doesn't, I know the valve is on the Ram version and I was thinking along those lines. Does the Jeep use the trans TMU? I know cars don't have the TMU.
 

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Discussion Starter · #13 ·
If your radiator is cool when this thing is overheating then coolant is not circulating. When it's overheating, is the fan running?
No heat thru the heater core and the Radiator is not hot ? Definitely a coolant flow issue.
Exactly. No heat coming off of radiator and no heat out of air vents when it's overheating indicates that there's no circulation happening, BUT when it's at normal operating temperature (cruising on the freeway and being careful of load), I will have full circulation (heat coming off of radiator and heat out of air vents). When it overheats, fans come on extremely high.

Thinking back, the issue started around the time that I had the dealer replace a leaking oil cooler hose. Is it possible that they accidentally got some sort of debris in the oil cooler when the hose was off, and thus causing an internal blockage within the oil cooler? Is there any way to test the oil cooler without fully replacing the oil filter housing and accompanying oil cooler?
 

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@Hoss7 it's funny you mentioned the oil cooler as I was thinking of it being a possibility. It does provide cooling to the engine.
Does anyone know if there is a thermostatic valve in the oil cooler?
 

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The oil filter adaptor and oil cooler on the Jeeps is different than the Rams. To my knowledge there is no external hose on the Jeep setup unlike the Rams I know on the Ram there is no thermostatic valve for the oil cooler.
 

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I cant think of anything other than an air pocket or perhaps a rag somehow ended up in the cooling system.

I had a truck that did something similar and it was air... Just cause they bled it with a special tool, doesnt mean they did it properly.
 

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I had a truck that did something similar and it was air... Just cause they bled it with a special tool, doesnt mean they did it properly.
I think the OP is doing the work himself. The vacuum bleeders for the cooling system are pretty simple to use, you sorta have to try to screw up using one. Unless the gauge is bad on it.
 

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I think the OP is doing the work himself. The vacuum bleeders for the cooling system are pretty simple to use, you sorta have to try to screw up using one. Unless the gauge is bad on it.
I hear ya but the symptoms are 100% indicating air lock.
 

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When your bleeding air out of the system, do you have the temperature selector in the heat position? If not you could have trapped air in the system.
 

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I wonder if @GDE could shed some knowledge about the cooling system, if it's prone to being air bound. They might be able to shed some light on the subject, could it be from a oil cooler not working??
 
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