Overheating problems with XJ - JeepForum.com
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post #1 of 4 Old 09-16-2016, 03:31 PM Thread Starter
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Overheating problems with XJ

Hello guys!!

I will try to explain the problem I had this morning with my Cherokee XJ with the lovely renix 4.0 engine... During the summer I had some overheating problems with the Jeep. Sorry for my poor technical english but this language is not my mother tonge... maybe you figured out from the first sentence.

Firstly, going for a route I noticed that the temperature indicator was about to get the red band and I stopped but the expansion vessel cracked leaking the cooling liquid. Bought a new one and changed the vessel and the thermostat. After two week I took again the Jeep to make another route and again the overheating issue. This only happens in ramps, never in plain road. I took it to a mechanic and he noticed that the radiator wasnt cooling enough and he changed it. The mechanic told me as well that maybe the cylinder head had a problem because after trying the car the cap of the expansion vessel was suddenly released leaking again the cooling liquid.

We refilled it but ... after leaving the mechanic shop we went for a ride and after asking the engine some efforts the cap was released again.

What you think this could be? Cylinder head? The cap is crap?

Best regards and hope the text is legible enough

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post #2 of 4 Old 09-17-2016, 12:50 AM
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It sounds as though you may have a leaking cylinder head gasket. I would recommend a compression check be performed to help diagnose the problem.

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post #3 of 4 Old 09-17-2016, 06:09 AM
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Only suspect the cylinder head or the head gasket after a complete and logical diagnostic check of the entire cooling system. Yes, the head gasket might cause those symptoms, but they are several less expensive and easier to change parts that may also be the cause of the symptoms. I might suspect the mechanical fan clutch or the water pump. Overheating at idle, or in slow moving traffic, points to the fan clutch as the cause.

If you are planning on keeping the Jeep you may want to consider installing the newer style radiator with the radiator cap and eliminating the expansion vessel. The newer style radiator with cap is more effective at cooling than the older style radiator.

Overheating can be caused by anything that decreases the cooling system’s ability to absorb, transport, and dissipate heat, such as a low coolant level, loss of coolant (through internal or external leaks), poor heat conductivity inside the engine because of accumulated mineral deposits in the water jackets or radiator, a defective thermostat that doesn’t open, poor airflow through the radiator, a slipping mechanical fan clutch, an inoperative electric cooling fan, a collapsed lower radiator hose, an eroded or loose water pump impeller or even a defective radiator cap.

The cooling system is a group of related parts that depend on proper function from each of its component parts to keep the engine cool. Service the cooling system and replace any under-performing or suspected weak parts. Any component part of the cooling system that is not fully doing its job will stress the others, and your engine will overheat. Temperature creep on the 4x4 trails, at idle, or in stop-n-go traffic, points to a weak or failing mechanical fan clutch or worn out water pump fins.

The most important maintenance item is to flush and refill the coolant periodically. Coolant should be replaced every 36,000 miles, or every two to three years. Anti-freeze has a number of additives that are designed to prevent corrosion in the cooling system, but they have a limited life span. The corrosion causes scale that eventually builds up and begins to clog the thin flat tubes in the radiator and heater core, causing the engine to eventually overheat.

-Use a chemical flushing/cleaning solution to remove mineral buildup or rust, flush with clean water, and then drain and fill the radiator with a fresh 50/coolant and water mix. With neglected cooling system you may have to flush several times.
-Inspect the radiator for mud/bugs/grass clogging the outside and mineral deposits clogging the inside. Clean or replace as needed.
-Replace the thermostat with a genuine Jeep 195* thermostat. Cheap thermostats are cheap for a reason.
-Replace the radiator cap if your Jeep has one. An old worn out radiator cap will allow boil overs and/or allow the coolant flash over into to steam. You will see the coolant temps suddenly jump from 210* to the Red Zone and back to 210* if your radiator cap is weak.
-Inspect/test or replace the mechanical fan clutch. A worn fan clutch will allow temperature creep at stoplights, in heavy traffic, and on the 4x4 trails. A fan clutch that “looks” OK is not the same as working OK.
-Inspect the electric cooling fan and the fan relay. Apply 12 volts and make sure the fan runs. Exchange the cooling fan relay with one of the others similar relays. Confirm that the e-fan starts when engine temps reach 215-218*.Repair or replace the fan or relay as needed.
-Inspect/test or replace the coolant temperature sensor that activates thee-fan.
-Replace the water pump. The pumping fins can deteriorate over time and the pump will not flow enough coolant to keep the temps under control.
-Inspect/replace the radiator hoses. Make sure the coiled wire is installed in the lower hose.

If you have covered all the points listed above and still have overheating issues, inspect and test the head for cracks and head gasket for leaks. Exhaust gasses entering the coolant can raise the temperature of the coolant or cause steam pockets in the coolant that will temporarily block the flow of coolant

Read more about cooling systems here –




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post #4 of 4 Old 09-18-2016, 06:29 AM Thread Starter
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Thanks for the quick replies!
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overheating , xj

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