2.8 CRD Cherokee KJ overheating when A/c on

John Todd · Aug 10, 2024

I wonder if anyone can help me with this? My 2005 Cherokee (Liberty) 2.8 CRD runs very well and the temperature gauge stays in the central position on the gauge. Even in 35C (it’s very hot here at the moment in SW France and 40C is forecast for Sunday) this doesn’t change.

However, as soon as I turn on the A/c the gauge almost immediately begins to move over completely to the overheat position and the engine boils over. There’s plenty of water in the system so it’s not that.

Any ideas anyone?

Thanks in advance,

John

KJowner · Aug 10, 2024

The heat exchanger for the AC is in front of the radiator, I would guess the additional heat is causing the issue.
Is it a problem when you are travelling at speed or just when you are stopped?
If its just when you are stopped then it's probably the viscous fan that has failed.
if its when you are driving you may have a partial blockage in the radiator liquid side, have you used anything except HOAT coolant? It can react and gell with other coolant.
Also check the Radiator isn't blocked with leaves, grass, straw etc, round here the farmers are harvesting and there is a lot of stuff blowing about.

KJowner · Aug 10, 2024

Oh and don't use water in the system, it must be HOAT antifreeze the engine is a wet liner design and other coolant will cause micro boiling and pinholes will develop in the liners wrecking it.

iceaxe1967 · Aug 12, 2024

Hello, when the AC button is pushed the electric fan in front of the radiator behind the grill, should come on instantly.
Check the fan relays under the hood in the engine compartment. I had a similar problem when I first bought my used CRD, what I did was gently pull up on the relays and they made a better connection so the terminals may be dirty on yours.
Hope this helps.

John Todd · Aug 12, 2024

KJowner said:
Oh and don't use water in the system, it must be HOAT antifreeze the engine is a wet liner design and other coolant will cause micro boiling and pinholes will develop in the liners wrecking it.

I have no idea what HOAT is and suspect that I won't be able to buy it here in SW France.

When I first bought the Jeep I completely drained and flushed several times the cooling system and then refilled with ordinary antifreeze bought from the local supermarket. That was about 2 years ago. When necessary I top up with the same product.

The comment about the electric fan is interesting because I'm fairly sure that it doesn't come on when I switch on the a/c. That's the first thing I will check tomorrow morning. Does the engine have to be running or should the fan come on if I turn on the ignition, turn on the fan and push the a/c button?

JMichael2006 · Aug 12, 2024

My front fan failed (old,corrosion,..), it would over heat climbing a grade. I replaced it with an aftermarket single speed the same size. It is back to running like it is supposed to. I just pulled the assembly. Removed the old motor and blade assembly from the Jeep mount. I then installed the new motor and blade in the old housing and wired both hi and low to the single wire. This way it runs whichever is providing power.

DadOSix · Aug 12, 2024

John Todd said:
I have no idea what HOAT is and suspect that I won't be able to buy it here in SW France.

When I first bought the Jeep I completely drained and flushed several times the cooling system and then refilled with ordinary antifreeze bought from the local supermarket. That was about 2 years ago. When necessary I top up with the same product.

The comment about the electric fan is interesting because I'm fairly sure that it doesn't come on when I switch on the a/c. That's the first thing I will check tomorrow morning. Does the engine have to be running or should the fan come on if I turn on the ignition, turn on the fan and push the a/c button?

John - HOAT is a technology in anti-freeze chemistry. Here across the pond, we see it at the dealer and also as Xerex-G05 coolant. Xerex being a brand name. THere is a special anti-corrosive additive in it to deal with the iron and aluminum components. Using the wrong coolant or mixing chemistries leads to sludge and gelling in the block and passages. Supposedly MB (mercedes benz) and G05 are interchangeable.

KJowner · Aug 12, 2024

iceaxe1967 said:
Hello, when the AC button is pushed the electric fan in front of the radiator behind the grill, should come on instantly.
Check the fan relays under the hood in the engine compartment. I had a similar problem when I first bought my used CRD, what I did was gently pull up on the relays and they made a better connection so the terminals may be dirty on yours.
Hope this helps.

European Jeeps don't have the electric fan fitted, everything relies on the viscous fan, a really stupid bit of cost cutting.... unless it was fitted to the later ones?? Mine is 2004.

HOAT in Europe is Comma Xstream G05.
Anything else will cause engine damage.
As far as I know Mercedes use OAT coolant so not compatible. JCB and Cummins use HOAT, not sure about Cat, the ELC1 is mystery fluid, no chemical data that I have seen.

JMichael2006 · Aug 12, 2024

Okay, didn't know the Euro versions didn't have Efans. I also installed the 10 blade fan and clutch off a Chevy v8. Check the image, it has all the p/n's to install a better setup.

2.8 CRD Cherokee KJ overheating when A/c on

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