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Discussion Starter · #1 ·
I have a 2001 4.0L Inline 6, the engine seems to run okay for its age for short distances and once on the highway no traffic. However, once I hit traffic temps sky rocket upwards of 230's. I get that these engines have an understood higher operating temp of about 210 but I feel like it should not skyrocket that fast..... Going to be flushing radiator, checking fan clutch and fan, and looking into a lower temp thermostat. Any other ideas??

I first thought the electric fan wasn't going but I heard that it only really goes on with AC or temps sitting solidly above 210.... have not gotten a chance to check it above 210 but are there any other checks that do not require pulling it and the shroud?

The Florida heat does not help my case but I wanted to know if anyone has found a fix to this problem of broken components or a remedy to old age? Thanks all!!!

Griff
 

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you have elec and engine driven fans...

The elec is set to operate at @218 ° OR a AC high 'high' pressure @ (I forgot).

So 220 ° is not high, (yes it worries all us older jeepers).

The flush always a good idea, be sure to use 195 ° thermostat,
be sure all shrouds are there.
Finally you are sure the elec fan comes on?

EDIT
I looked up the specs elec activated at 223 ° ECT or the AC pressure reaches 300psi.
 

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195* is the specified thermostat, a lower temp stat only causes the PCM to run rich and waste gas, and will have no effect upon the operating temps.

Suspect weak or worn out cooling system parts. My 2000 runs at 195-210* even on the hottest days.

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.

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 worn out mechanical fan clutch, an inoperative electric cooling fan, a collapsed lower radiator hose, an eroded or loose water pump impeller, leaky frost plugs, or even a defective radiator cap. None of the cooling system parts last forever.

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.

-Inspect the radiator for mud/bugs/grass clogging the outside and mineral deposits clogging the inside. Clean or replace as needed.
-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 the e-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.
-Inspect all of the frost plugs in the block and the ones on the backside of the head for rust holes and coolant leakage.
-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 50/50 coolant and water mix. With neglected cooling system you may have to flush several times.
-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 not hold system pressure which can cause boil overs and/or allow the coolant flash over into to steam. You will likely see the coolant temps suddenly jump from 210* to the Red Zone and back to 210* if your radiator cap is weak.

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
 

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Discussion Starter · #4 ·
you have elec and engine driven fans...

The elec is set to operate at @218 ° OR a AC high 'high' pressure @ (I forgot).

So 220 ° is not high, (yes it worries all us older jeepers).

The flush always a good idea, be sure to use 195 ° thermostat,
be sure all shrouds are there.
Finally you are sure the elec fan comes on?

EDIT
I looked up the specs elec activated at 223 ° ECT or the AC pressure reaches 300psi.
Thanks for the helpful info!! I direct wired the elec fan to see if it works and it does not. Also did not activate and car was reaching ~230. However the connector is female off the fan and any OE or OEM fan has male coming off the fan so not sure why that is...
 
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