04 Gr Cherokee 4.0 - Complete Cooling system replacement and still overheating!

[MDB1056]

My daughters 2004 Grand Cherokee (4.0) a week ago Friday threw a code - said Thermostat, so I replaced the thermostat, OEM 195, easy job. Drives for a week all is fine. Last Friday it overheats - she has it towed to my house. No leaks, system is full, pressurized, all looks fine. When she bought the car 3 yrs ago it was loaded with stop leak, which I told her was a big concern but it was too late. But that was 3 yrs ago and it's been fine. My first thought is that when I changed the t-stat and replaced a lot of coolant that it stirred stuff up inside and maybe the t-stat was stuck. Took it out, looked fine, put it in water, heated, it opens fine, etc, cabin is smokin hot, etc. Reinstalled t-stat, new gasket. On to plan B - radiator, was original, and with all the stop leak thinking ok that has to be clogged and the problem. Replaced it yesterday, refilled the system again, still overheating. Water pump is only item left , showing no signs of being bad, not weeping, pulley is true, no noise, but replaced it anyway. Refill again, STILL overheating. UUUUGGHHHH......

I do not think it's a head gasket as shows none of the expected signs such as exhaust vapor, no coolant in the oil (its clean), no oil found leaking, idles fine, starts fine. Not likely a temp sensor as that would throw a code and there are no codes. Now - the only thing I've noticed is that the electric fan doesn't seem to be turning on until it's pretty hot past the 195 -210 operating range, and I don't know if the fan is functioning at full capacity as it's not my car, but the fan is essential to cool if just sitting idling but would that alone cause an overheat? There's nothing left as there are not that many moving parts to a cooling system. Again for the past 3 yrs the car has been fine - no issues, and even a week after t stat change.

Would REALYY APPRECIATE and insight here as I'm at wits end on this one. The only good news is it's easy to work on, but I'm tired of working on it.

THANKS!

 

[ndnatty]

A properly functioning fan and shroud will definitely keep the temp down. I left the shroud off my cj7 and it wouldn’t cool at all. Put it back on, and cool as a cucumber.


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[JPNinPA]

There are a few things you didn't mention.
Did you burp the system?
If any air gets trapped in the engine it quickly expands and causes pressure to rise.

Is the expansion tank hooked up, not leaking and full?

The cabin heater is blowing hot and not clogged?

Did you replace the radiator cap with a new 18 lb cap?

Did you see it overheat? When does it happen?
After highway driving when driving less than 30 mph?
After you shut the car off?
On the highway or streets no matter what mph.

When cold if you open the rad cap and start the vehicle watch to see any bubbles or a stream of foamy small bubbles.

Check your oil for milkshake.

Look at the casting numbers on the head 331 crack near 3&4



Regards,
JPNinPA

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[MDB1056]

Thanks @JPNinPA. Coolant fill tank is connected and not leaking and full. Cabin gets smokin hot so heater core is not an issue, yes new radiator cap too, oil is 100% clean, and no signs of head gasket (poor idle, exhaust vapor, mily oil, etc) it over heats just idling in my garage as after each addition (tstat, radiator, w pump) I refill the system with 50 50 and start it and let it run and watch. After last parking it uphill yesterday and letting it overflow to get air out I'm going to top it off this morning and start it and see what happens. Will advise. Will check the temp at which the fan engages. I wasn't driving it when it overheated - daughter was - said it got hot, light came on, whe pulled into starbucks parking lot and shut it off. Called me and a tow. I arrived and looked it over before tow arrived, no leaks, system still full, pressurized. Wondering if a cooling passage is clogged in the block or head from the stop leak, as again it was a week after changing the T stat that this happened. Will check the head for crack as best I can

There are a few things you didn't mention.
Did you burp the system?
If any air gets trapped in the engine it quickly expands and causes pressure to rise.

Is the expansion tank hooked up, not leaking and full?

The cabin heater is blowing hot and not clogged?

Did you replace the radiator cap with a new 18 lb cap?

Did you see it overheat? When does it happen?
After highway driving when driving less than 30 mph?
After you shut the car off?
On the highway or streets no matter what mph.

When cold if you open the rad cap and start the vehicle watch to see any bubbles or a stream of foamy small bubbles.

Check your oil for milkshake.

Look at the casting numbers on the head 331 crack near 3&4



Regards,
JPNinPA

Sent using TapTalk

 

[mark sr]

Was it just the temp gauge that caused her to pull over or where there other signs of overheating? 35 yrs ago my flathead ford always showed it getting dangerously hot. On mine it turned out to be a mismatched gauge and sending units. Just one more thing for you to check.

 

[JPNinPA]

^^ good point^^ temp sending unit could be failing.

She did the right thing by pulling over.

Besides parking on a hill there are thermos with a hole at the too to let air through.
Also squeezing the top hose while warming helps move the air out.

I would think with replacing the radiator the space between the rad and condenser coils was clean and the condenser coils are clean.
Did you use OEM radiator. OEM has a higher fin density than other brands.
Lower hose is not blocked or crushing at idle?




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[MDB1056]

Problem solved. We missed the obvious up front. Issue was the fan. replaced today with new Dorman assembly - super simple - plug & play, and all is well. I missed that regardless of all the other components if there's no air movement through the radiator the car will overheat. It didn't occur to me until after the water pump. Not knowing the vehicle I didn't know the fan or if / when it runs etc. So my daughter has a COMPLETELY new cooling system of thermostat, housing, radiator, cap, water pump, and fan. Should be good for a while. All in parts total is only about $290, and all with lifetime warranties. Interestingly learned also that the fan is connected somehow to the AC working well as when this was going on the AC would only start to cool then shut down and blow warm. With this fixed it runs fine now. Really have to say that this 04 Grand Cherokee with the 4.0 is a pleasure to work on compared to SO many other vehicles as everything is easy to get to which makes a HUGE difference.

Thanks so much for the traffic! Great forum. I'll be back I'm sure for another item soon!

 

[TerryMason]

Glad you got it fixed. Although it's a pain to change all that stuff, you would have spent more than $290 at a mechanic's.

 

[MDB1056]

Glad you got it fixed. Although it's a pain to change all that stuff, you would have spent more than $290 at a mechanic's.

Woudl have spent a TON more. The work was easy as again this vintage (04) jeep is super easy to work on. Frustration was in the time it took to run it down to being fixed. Always check the fan at all points in the process when dealing with a cooling system issue, which I didn't pay attention to as I shoudl have . Hopefully this will help out someone else down the road.