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Old 04-08-2019, 08:21 AM
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Location: Fulshear TEXAS
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Overheating Issues

89 with 4.2 that I've owned about 1 year.

I already had coolant sitting in the garage waiting to do a system flush... Jeep was always running right about 200. Last week the temp started creeping up to 210-220. I went ahead and ordered a new pump, thermostat and fan clutch.

Thursday I added some cleaning agent and Friday, after about 2 hours run time, I started removing parts. I flushed the radiator and block with the water hose until everything ran clear. Unfortunately I broke a bolt, so I wasn't able to reassemble everything until Saturday night. Sunday afternoon I started to refill everything and had a leak. The thermostat housing had cracked when I was torquing the bolts. Sunday afternoon I went and replaced that. To give the gasket sealer time to cure, I waited to finish filling the system until this morning.

And... when I test drove her this morning, after filling and burping, she still went up to close to 220. I had to get to work, so no time for any real troubleshooting. But, the radiator was hot so I had flow flow. I confirmed it's the correct pump (matched the one I removed). When driving, temp would cool down and then creep up when stopped, going between about 210-220. I didn't get over 30 mph.

I suspect it could be the fan clutch. Cold you could turn it but no real "spin". Warm it turned much easier. I expected this to work the opposite way, where it would spin more freely when cold?

Any opinions?

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Old 04-08-2019, 08:57 AM   #2
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In theory, yes that's the way it should work, although a failing fan clutch tends to freeze up rather than spin freely.

In my experience no matter what you do in the driveway, nothing gets the air completely out of the system like a good run at operating temp to get all the air out of the block, heater core and hoses and into the radiator where the radiator cap can do it's job and bleed the air into the reservoir and refill the radiator.

You didn't say what all you replaced with the pump, but a proper job well done includes pump, clutch, thermostat and cap, as well as check and replace hoses if necessary. Think of it as "If one part is weak, the complete system should be replaced to eliminate all weak links.

Let us know how your ride home goes, you may have already purged the system on the way to work this morning...

Good Luck...

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Old 04-08-2019, 09:09 AM
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Thanks! I replaced everything but the hoses, including the clutch.

I have the last bit of coolant in the jeep, so I'll try burping again.

You're saying it should spin more freely cold than hot?
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Old 04-08-2019, 10:02 AM   #4
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Open the hood when warmed up, like when you get home from work. Get out and watch the fan, reach in and turn off the engine. A properly working fan will turn about 3-5 turns if it is properly working.
This is what I read before I did the water pump/clutch change.

If you just installed a new clutch, I would investigate other things.
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Old 04-08-2019, 03:16 PM   #5
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Make sure you got the correct water pump, some have forward flow and some have reverse flow.

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Old 04-08-2019, 07:03 PM
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Picked up a IR thermometer on the way home. Loos like the sensor or gage is the culprit. I'll check them out later, once I've researched how to test them.

Sorry I forgot to turn my phone.
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Old 05-08-2019, 08:29 AM   #7
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Is that the original radiator still? Could be clogged somewhere too...

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