4.0 Cooling Issues

Hi Flivver250,

Thanks for the clutch tip. It was replaced during the rebuild, so it is about a month old. I think that part is still good. The reason why I don't want to just replace all the components and call it done is because I really want to find out the cause, reasons and learn :) Swapping parts is easy, correctly diagnosing the problems is still hard for me. I am learning.
Sounds like the only parts that aren't new are the radiator, water pump and hoses. All are normal maintenance items. My friend's TJ started overheating. He flushed the system, replaced the fan clutch and the radiator as both were sketchy looking. It still ran a bit hot, but better. I looked at the coolant he used and I did not like the color/appearance and I had an epiphany. He bought some clown brand that had an American flag on it and I had suspicions of phony knock-off product. We drained the system and refilled it with the correct coolant with impeccable lineage and the cooling system functioned flawlessly. It is also not uncommon to get brand new defective thermostats. Those can be tested by placing them in a pan of water with a thermometer and slowly heat and note the temperature when it opens.
 
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Sounds like the only parts that aren't new are the radiator, water pump and hoses. All are normal maintenance items. My friend's TJ started overheating. He flushed the system, replaced the fan clutch and the radiator as both were sketchy looking. It still ran a bit hot, but better. I looked at the coolant he used and I did not like the color/appearance and I had an epiphany. He bought some clown brand that had an American flag on it and I had suspicions of phony knock-off product. We drained the system and refilled it with the correct coolant with impeccable lineage and the cooling system functioned flawlessly. It is also not uncommon to get brand new defective thermostats. Those can be tested by placing them in a pan of water with a thermometer and slowly heat and note the temperature when it opens.
I will actually test the original I replaced that way and if it is still good, I will keep it!!!

The coolant is Zerex G05 50/50.
 
I'm OCD, I'd consider the idler pulley and belt tensioner while you are stripping it down. Not expensive, and it is good preventive maintenance. Save the old ones as emergency spares. Those usually squeal a while before failure, giving you advanced notice, but there is a sense of comfort with a scorched earth approach.
 
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I just did a coolant system overhaul myself. Generally speaking, if you are overheating while driving at highway speeds look towards a coolant flow issue (water pump, loose belt, radiator, clog somewhere). If you are overheating at idle but normal temperature while driving look to an airflow issue (mud in radiator, clutch fan).
 
Stepping in a day late here, but I wouldn't be surprised if the cause was using straight water in the system. It's called coolant for a reason. All that vapor pressure caused by the low boil point of water could be what caused your radiator to fail. How far south do you live in Ca? If you normally run just under 210* with coolant, and you know water boils at 212*, and that even a simmer will make steam, what did you expect to happen? Even after seeing boiling water in the coolant reservoir?
The original pump is likley well worn. The impeller blades actually wear back with use. I don't know why they aren't considered a wear item.🤷‍♂️ But if you are doing engine work and it has 100,000 miles + on the pump, you (we all) should replace the pump and thermostat. Hoses too. If you think the front belt has a hard life, think about what those hoses have to go through. Replace the ones to the heater core as well.
I too am curious as to why there are no good aluminum radiators for the Jeep.❓❓ It seems the ones made for the Camaro Mustang and Pick-Ups all do well. What is different about a Jeep that causes apparent problems? Best of luck with the repairs. Out of curiosity could you check on how much wear is on the pump impeller compared to new? I've got 145k miles on what appears to be the original pump. Thanks.👍
 
I'm OCD, I'd consider the idler pulley and belt tensioner while you are stripping it down. Not expensive, and it is good preventive maintenance. Save the old ones as emergency spares. Those usually squeal a while before failure, giving you advanced notice, but there is a sense of comfort with a scorched earth approach.

That's exactly what I did, just 2 weeks ago when I rebuilt my entire cooling system.
 
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That's exactly what I did, just 2 weeks ago when I rebuilt my entire cooling system.
I like new parts and the task of installation. This week I am installing new clutches in my rear diff and a new Bosch fuel pump. Can't think of a good reason to wait for either to fail. I bought a rebuild kit for my low mileage transfer case. I'll do that this summer when it is too hot to go out in the desert. These very procedures are just as enjoyable as running the rig.
 
I like new parts and the task of installation. This week I am installing new clutches in my rear diff and a new Bosch fuel pump. Can't think of a good reason to wait for either to fail. I bought a rebuild kit for my low mileage transfer case. I'll do that this summer when it is too hot to go out in the desert. These very procedures are just as enjoyable as running the rig.

Yes! Scheduled maintenance is #1 for any vehicle, preventative maintenance is #2.
 
I too am curious as to why there are no good aluminum radiators for the Jeep.❓❓ It seems the ones made for the Camaro Mustang and Pick-Ups all do well. What is different about a Jeep that causes apparent problems? Best of luck with the repairs. Out of curiosity could you check on how much wear is on the pump impeller compared to new? I've got 145k miles on what appears to be the original pump. Thanks.👍
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I've read a number of threads on factory vs. aftermarket radiators, and some seem to think that it's the very nature of our Jeeps that make aftermarket not reliable.
With most other vehicles, their ride is a lot easier on the vehicle than ours are. Jeeps ride a lot rougher and shake a lot more than they do.
The plastic housing has just enough flex to it to allow for a bit of movement. A all aluminum unit will be ridgid. Aluminum is great stuff, but it is relatively brittle and will not flex.
As far as I've read, nobody that has gone with an aftermarket has stuck with one, except for the guys that stubbornly refuse to admit that they were wrong, and don't mind replacing it every couple years, (under warranty of course).
 
If you do dive in for the water pump check everything else while you are at it.
Fan clutch
All rubber hoses, even the heater hoses.
Any metal tubes (my 2.5 has a metal tube for the heater), I replaced it, lots of internal corrosion.
No sense putting nice fresh fluid in and then finding you have a bad hose.
Temperature sensor
 
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Stepping in a day late here, but I wouldn't be surprised if the cause was using straight water in the system. It's called coolant for a reason. All that vapor pressure caused by the low boil point of water could be what caused your radiator to fail. How far south do you live in Ca? If you normally run just under 210* with coolant, and you know water boils at 212*, and that even a simmer will make steam, what did you expect to happen? Even after seeing boiling water in the coolant reservoir?
You do understand that the radiator cap increases the pressure in the cooling system right? Do you also understand that water under pressure boils at a higher temperature that at atmospheric pressure? Did you know that coolant doesn't actually cool better than straight water?
 
If you do dive in for the water pump check everything else while you are at it.
Fan clutch
All rubber hoses, even the heater hoses.
Any metal tubes (my 2.5 has a metal tube for the heater), I replaced it, lots of internal corrosion.
No sense putting nice fresh fluid in and then finding you have a bad hose.
Temperature sensor

Fan clutch is new
Hoses are new
The metal tube is not (I will check when I replace the pump)

Cheers
 
I just did a coolant system overhaul myself. Generally speaking, if you are overheating while driving at highway speeds look towards a coolant flow issue (water pump, loose belt, radiator, clog somewhere). If you are overheating at idle but normal temperature while driving look to an airflow issue (mud in radiator, clutch fan).

Appreciate the tips! Right on :)
 
I'm OCD, I'd consider the idler pulley and belt tensioner while you are stripping it down. Not expensive, and it is good preventive maintenance. Save the old ones as emergency spares. Those usually squeal a while before failure, giving you advanced notice, but there is a sense of comfort with a scorched earth approach.

I will check them out and most likely replace them as well. Cheers
 
Just as likely your temperature sender is off as any one of those cooling system parts is bad. I've never found it much use to stare at the needle. You might get an OBD scanner and see what the sensor is actually reading, the ELM327 type are only a few dollars. My gauge looks like yours sometimes on the freeway but my scanner says 198 and 210 on my gauge is reported as 195 coolant temperature. Changing out all that stuff isn't a bad idea but I'd also do a reality check on how serious your problem really is before you dump much more money into it. If it ain't overheating it ain't broken and your gauge isn't showing overheating to me.
 
Just as likely your temperature sender is off as any one of those cooling system parts is bad. I've never found it much use to stare at the needle. You might get an OBD scanner and see what the sensor is actually reading, the ELM327 type are only a few dollars. My gauge looks like yours sometimes on the freeway but my scanner says 198 and 210 on my gauge is reported as 195 coolant temperature. Changing out all that stuff isn't a bad idea but I'd also do a reality check on how serious your problem really is before you dump much more money into it. If it ain't overheating it ain't broken and your gauge isn't showing overheating to me.

I do have a scanner. I can compare the gauge to the data from the scanner :). It is not a bad idea for troubleshooting the gauge!
 
Stepping in a day late here, but I wouldn't be surprised if the cause was using straight water in the system. It's called coolant for a reason. All that vapor pressure caused by the low boil point of water could be what caused your radiator to fail. How far south do you live in Ca? If you normally run just under 210* with coolant, and you know water boils at 212*, and that even a simmer will make steam, what did you expect to happen? Even after seeing boiling water in the coolant reservoir?
The original pump is likley well worn. The impeller blades actually wear back with use. I don't know why they aren't considered a wear item.🤷‍♂️ But if you are doing engine work and it has 100,000 miles + on the pump, you (we all) should replace the pump and thermostat. Hoses too. If you think the front belt has a hard life, think about what those hoses have to go through. Replace the ones to the heater core as well.
I too am curious as to why there are no good aluminum radiators for the Jeep.❓❓ It seems the ones made for the Camaro Mustang and Pick-Ups all do well. What is different about a Jeep that causes apparent problems? Best of luck with the repairs. Out of curiosity could you check on how much wear is on the pump impeller compared to new? I've got 145k miles on what appears to be the original pump. Thanks.👍

Straight water is actually a better coolant for heat transfer then glycol is, typically in system design and engineering glycol systems can reduce efficiency by up to 10% and if it wasn't for the fact that it freezes we would all be using water. Also water in a closed loop under pressure water will not boil and produce vapor pressure. If the radiator cap is a proper 18lb and working water will not cause any issues.
 
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Straight water is actually a better coolant for heat transfer then glycol is, typically in system design and engineering glycol systems can reduce efficiency by up to 10% and if it wasn't for the fact that it freezes we would all be using water. Also water in a closed loop under pressure water will not boil and produce vapor pressure. If the radiator cap is a proper 18lb and working water will not cause any issues.
You will rust out your engine in about two days, this is not good advice. When I was young and a less than experienced mechanic I used water after doing a head gasket and in less than a month the cooling passages in the head corroded through to the combustion chamber.
 
You will rust out your engine in about two days, this is not good advice. When I was young and a less than experienced mechanic I used water after doing a head gasket and in less than a month the cooling passages in the head corroded through to the combustion chamber.
Amazing that there are millions of buildings in this world that use straight water (with inhibitors) in steel and cast iron systems for heating and cooling throughout the world and they continue to work after a hundred years, but not in Jeeps.

I did not suggest or advise that using water was proper, only wanted to clarify the statement about the possibility that water reduced the cooling capacity when it will not.
 
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