Engine Overheating Diagnosis Advice

[Melanie]

I have 2002 Jeep Liberty KJ.

My engine overheated today after a 3km uphill drive. It started steaming a lot from under the hood, and then when I opened her up, I saw that she was boiling a lot of coolant from the coolant reservoir and onto the ground.

The temperature gauge on my dash registered a normal temperature (halfway between cold and hot). I had the heater on inside, and it was plenty warm on this cold day.

I stopped the engine immediately and haven't driven her from that spot.

Does anyone have any ideas as to how I can tell if it is the thermostat, the temperature sensor (is this even a separate thing), the radiator, or the water pump that is the issue?

I did get a new check engine light code that I haven't seen before - P0837 - am not sure if this is related or whether it is a coincidence. There has been a code of P0442 that has always been there that is still there.

In the last few days before the engine overheated, I also thought I smelled coolant coming from the car - am not sure if this is related either, as I drove 200km on a highway and in the city after that, with no issues.

Any thoughts would be greatly appreciated!

 

[LibertyTC]

How does the dipstick oil look, any bubbles or coolant contamination?
Sounds like you may have a few issues going on,a coolant leak introduces air, and you could now be low on coolant.
Hoat coolant or zerex g05 only.
Fill thru the air bleed hole at top rad hose, and pressure test it.
If it passes pressure test, a Mopar thermostat only should be used.
New hoses, waterpump are all good candidates for restoration potentially.
the 0837 code could be related to 4x4 position sensor?
The 0442 leak sometimes are difficult to track down, and a smoke machine will help in identifying location.

 

[Melanie]

Thanks LibertyTC for your response. I filled up the coolant through the reservoir and felt the top hose at the radiator get more solid the more I filled it. Took approx. 4L of coolant to replenish the system. I then bled the system by opening the bleed hole, while the engine was running, and allowing air bubbles to escape.

I allowed the engine to run for a while and monitored the Temperature gauge. The Temperature gauge slowly heated up to the middle and the jeeps air began blowing warm inside and eventually hot.
I took notice that the top hose became more solid when i gave it gas. I also noted when i squeezed the top hose(going from the engine to the rad) - the bottom hose (from the rad to the engine) felt like it had coolant flow within it, leading me to believe there is no blockage in the radiator. My big concern is that the bottom hose remained cold for some time while the top hose became very hot. It is much colder closer to the radiator whereas its a bit warmer closer to the engine. Does this maybe mean the thermostat may not have opened? I allowed the engine to run for 10 minutes and the fan never kicked in. The fuse is good but no idea where the relay is located.

Also I had removed the coolant overflow cap when the engine was running warm, and noted a little, steam or exhaust coming from the tank and a bit of tank discolorizution. The coolant wasn't bubbling and the rear exhaust doesn't have any smell or indication of burning coolant. The system was pressure tested and held pressure at 12psi for a fair amount of time.

I felt confident after purging the system to drive the vehicle home about 10 minutes and had no issues. I did smell a little coolant from the interior fan, but that may be residual coolant burning from when it overheated yesterday. I cleared the OBD2 codes, check engine light is off and no codes returned.

My conclusion is that the Thermostat is not engaging and also the fan is not triggering. Could it be the switch to trigger the fan is located on the "closed" side of the thermostat and since the hot coolant is not passing the switch the fan is not triggering?

Trying to find a Mopar thermostat but Im 2 hours from any major city and the local parts store here only carries Gates for my vehicle. They say it is OEM replacement and shouldn't be a problem.

 

[tommudd]

I live 2.5 hours from any major city, I just order online
Use only the Mopar thermostat, do not listen to what the computer punchers tell you

 

[LibertyTC]

The electric fan should come on when any of the AC/ * positions selected. Does it come on?
2002 may have the external relay block, I'm tired right now cant remember, I know my 04 has hi-low relay's in under hood fuse panel.
Also with AC off, the electric fan does not come on until 227F approximately, need on ODD2 gauge/ reader to see exact temps.
If the thermostat was stuck in open position, there should be an associated OBD2 code, triggering an engine light, too long to warm up....

 

[jeeptorino68]

2002 does have the external fan relay. Mounted low by the battery tray. By the "frame rail"

 

[Melanie]

Going to pull the Relay and test

2002 does have the external fan relay. Mounted low by the battery tray. By the "frame rail"

The fan does not operate when I turn the AC on. Nor was the fan operating when I had overheated...so Im leaning now more to a fault in the fan circuit.

When I wired the fan to 12V, it operates. I pulled the relay, mounted by the battery tray, and tested it by adding power to the smaller leads. Without power the larger leads had an incomplete circuit and with power the larger leads registered a complete circuit. Although I didn't hear any relay clicking, I believe the relay is functioning correctly. I am going to check tomorrow if I get a voltage drop at the connector to see if it is actually getting a voltage supply when the AC is on.

If it does not I think next I need to find the switch that triggers power to the relay. Do you know if it is the Temperature sensor that triggers the relay, or something else?

 

[Melanie]

The electric fan should come on when any of the AC/ * positions selected. Does it come on?
2002 may have the external relay block, I'm tired right now cant remember, I know my 04 has hi-low relay's in under hood fuse panel.
Also with AC off, the electric fan does not come on until 227F approximately, need on ODD2 gauge/ reader to see exact temps.
If the thermostat was stuck in open position, there should be an associated OBD2 code, triggering an engine light, too long to warm up....

If the thermostat is stuck in the closed position would a code get thrown? I took it for a longer ride on the highway with no issues and noticed the bottom hose of the radiator has got a bit warm. So now im thinking that coolant is circulating through the radiator and engine. Im leaning more towards a fault in the fan circuit. I just do not understand why my temperature gauge inside the vehicle was not registering HOT when the engine overheated and started spraying coolant from the overflow. Do you think the temp sensor can register cold and warm but not hot and therefore not triggering the fan relay? Is it even the temperature sensor that sends signal to the fan relay or does something else trip the circuit?
Thanks again for your response.

 

[jeeptorino68]

I dont think the gauge is driven by the same sensor that triggers the fan.
FYI there is a heavy duty fan relay you can get for the early years. Google it You will find info in it. It has a bigger cooling heat sink on the relay. I upgraded to this one on my 2002

 

[Melanie]

I dont think the gauge is driven by the same sensor that triggers the fan.
FYI there is a heavy duty fan relay you can get for the early years. Google it You will find info in it. It has a bigger cooling heat sink on the relay. I upgraded to this one on my 2002

Found this Wiring on youtube... looks like the temp sensor connects to the pCm which then sends the signal to the relay.

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[LibertyTC]

Luckily I have an OBD2 scan gauge to read the temp sensor (FWT) Fahrenheit water temperature.

You must be registered for see images attach

The fan should turn on in Any AC* position.
Since the fan does not come on in AC modes, it probably is the fan or relay.
You also need an OBD2 scan gauge/ water temp reader to see if it is reading correctly.
The dash gauge can be misleading and is not that accurate, not to be relied upon.
The computer reads the temp sensor and when it reaches 227f in non a/c modes, the electric fan should come on, if it is reading & working correctly.

 

[Melanie]

Luckily I have an OBD2 scan gauge to read the temp sensor (FWT) Fahrenheit water temperature.

The fan should turn on in Any AC* position.
Since the fan does not come on in AC modes, it probably is the fan or relay.
You also need an OBD2 scan gauge/ water temp reader to see if it is reading correctly.
The dash gauge can be misleading and is not that accurate, not to be relied upon.
The computer reads the temp sensor and when it reaches 227f in non a/c modes, the electric fan should come on, if it is reading & working correctly.

On further inspection, I removed the temperature sensor connector and shorted out the pins - the fan did not go on (key in position 2, AC* On). The fan did however go on without the sensor connected and with the engine running.

Furthermore, I was also able to hook up my Bluetooth OBD2 and run the Torque app to monitor the coolant temp. When the temperature rose to 105C approx 221F the fan did kick in.

I now believe the temp sensor and relay are working as should but still a little stumped as to why it overheated and why the fan had not kicked in when it overheated and spewed coolant everywhere from the coolant overflow tank, and why the AC* does not trigger the radiator fan.

Perhaps my coolant tank cap loosened under pressure which extremely raised the coolant level.

Any thoughts appreciated!

 

[uss2defiant]

The e-rad fan only comes on at certain conditions.

OPERATION
The electric radiator cooling fan is controlled by the Powertrain Control Module (PCM) through the radiator cooling fan relay. The PCM regulates fan operation based on input from the engine coolant temperature sensor, battery temperature sensor,air
conditioning select switch and vehicle speed. The fan is not energized during engine cranking regardless of the electrical input from the temperature sensors and ,air conditioning switch. However, if engine operation conditions warrant fan engagement, the fan will run once engine starts.

Vehicles Equipped with AC:
In addition to using coolant temperature and battery temperature sensor to control cooling fan operation, the cooling fan will also be engaged when the ,air conditioning system is activated. The relay is also energized when, air conditioning is selected and coolant temperature is above 95° C ( 203° F), or , air conditioning is selected and battery temperature sensor is above 41° C (106°F). It will then de-energize when , air conditioning is selected and coolant temperature is below 92° C (198° F), or , air conditioning is selected and battery temperature is below 38° C (100° F).

 

[daves06lrenegade]

The coolant system is taxed ... more so under a load condition like climbing a long grade... Under normal conditions a questionable radiator may operate OK but when placed under a heavier load it may not be able to cool the engine...
We know the fan works and from what I read it doesn't overheat sitting so I would believe the water pump is also OK... The comment of the heat from the HVAC being HOT could also indicate a bad radiator as the car was dumping the extra heat in the heater core... Radiators do get plugged over time and become less efficient... Have a radiator/heater core shop check the radiator with a infrared temperature gauge for blocked sections of the radiator core... They can "see" if/where it has failed...
I bought a "Chinese" brand replacement for my 06 Liberty and it was very inexpensive (under $70) and has held up so far for one and a half years...
I'm satisfied... Dave

 

[tommudd]

The coolant system is taxed ... more so under a load condition like climbing a long grade... Under normal conditions a questionable radiator may operate OK but when placed under a heavier load it may not be able to cool the engine...
We know the fan works and from what I read it doesn't overheat sitting so I would believe the water pump is also OK... The comment of the heat from the HVAC being HOT could also indicate a bad radiator as the car was dumping the extra heat in the heater core... Radiators do get plugged over time and become less efficient... Have a radiator/heater core shop check the radiator with a infrared temperature gauge for blocked sections of the radiator core... They can "see" if/where it has failed...
I bought a "Chinese" brand replacement for my 06 Liberty and it was very inexpensive (under $70) and has held up so far for one and a half years...
I'm satisfied... Dave

Buy a lottery ticket, you are just lucky its lasted this long ( the chinese rediator) Have seen people go through 11 of them in 2 years time, bought Mopar, no more isses

 

[LibertyTC]

X2 Mopar Rad only please!

 

[jeeptorino68]

Everyone on here makes the mopar stuff out to be the only parts that work. Radiators. Rear upoer control arms, etc. I have not had that experience....maybe I am lucky too though.
If you dont get a mopar radiator, get one with the best warranty you can from a local parts store so warranty is easy.

 

[HoosierJeeper]

I had a Spectrum one last about 3 years/60k before leaking at the seems.

 

[mrlavalamp]

my Spectra radiator has managed to complete 2 summers in hell.

I paid $84 for it in july 2017 and when i bought it they claimed it had thicker blah blah blah with extra ribs for her pleasure more reinforcement. Now that my 24 month warranty is over, I will probably replace it in the spring.

Looks like the mopar rad is only $185 right now so not like most parts where the OEM is 10x the cost of aftermarket.


Everyone has their preferences and sticking points. There are some people who will say anything Chrysler related is garbage and not to be trusted under any circumstances, and the only vehicles they buy are toyotas or fords or some other brand.

 

[kejobe]

I have some aftermarket radiator in mine. So far, so good. Been about a year now, but not many miles as of yet, only 2-3000 or so.