2012 journey 3.6 liter overheating

[phoenix1151]

Wifes vehicle overheated today.  Had to stop and add significant coolant volume but it still started to overheat at speeds of 70-80 km/hr but held it's own at up to 60-65 km/hr on level ground while starting to rise on significant uphill slope even at 60-65 km/hr.  The coolant reservoir is still full.  Was going to drop it off at auto shop but decided to limp home at 60-65 km/hr.   We previously added Rislone leak stop to address a slow loss of coolant that seemed to work well for 2-3 months.  Also, the vehicle has had very limited heat from the heater core for some years now despite me trying multiple times to flush it last year (both tubes did get hot and the heat/cool damper works).

 

  Q1 : does ALL coolant flow through heater core then to the engine (i.e. in series) with no other route?

 

I'm wondering that because the overheating seems to be proportional to speed (heat transferred in), if the answer to Q1 is yes, then the heater core could be getting more clogged over time limiting coolant flow to the point of the thermostat being full open yet the cooling system can only handle the heat of 60-65 km/hr.  If so, I'm tempted to "jumper" the two heater core pipes together (since it doesn't heat the car anyway) and test run it.

 

Would appreciate comments beforehand.  Thanks.

[phoenix1151]

I meant "jumper" the two heater core HOSES together

[Dean H]

Slow down........

 

Need more information first.

 

Q1 - Do you have the EVIC screen in between the tachometer and the speedometer?

 

Select to display engine coolant temperature.

 

I need to know the engine coolant temperature. That it runs at during the speeds you are referring to.

 

What temperature is it when you say it's overheating.  

 

What exactly happens when you say it's overheating? 

 

 

Edited September 5 by Dean H

[phoenix1151]

No actual coolant temp readings, just needle on temp gauge.

[14WhiteRTRallye]

 

[John/Horace]

Is cooling fan going to high speed when a/c is on?  Is it original radiator and thermostat still?  Cooling system has had a pressure test.?

[phoenix1151]

I appreciate contributions but can someone answer the question I actually asked?  Does ALL coolant flow through heater core then to the engine (i.e. in series) with no other route?

[phoenix1151]

I've heard that the heater core is the primary circuit for coolant flow until the thermostat opens up, then flow can go through both the engine and heater core.

I haven't done any investigation re the overheating yet since my concern was just getting home yesterday with one eye on the road and one on the temp gauge.  Thunderstorms today so maybe some snooping tomorrow but it will be somewhat superficial as I'm not capable of anything too involved any more.

[Dean H]

 

If you have the instrument cluster below on the DJ.

 

Use the steering wheel keypad

arrows and back button.

 

To access any available gauges in the menu.

 

Flow chart 3.6.

 

1 - RADIATOR

2 - RH CYLINDER HEAD

3 - THERMOSTAT 

4 - WATER CROSSOVER

5 - LH CYLINDER HEAD

6 - REAR HEATER CORE

7 - FRONT HEATER CORE

8 - OIL COOLER

9 - WATER PUMP

10 - CYLINDER BLOCK

 

I found this on the 2016 DJ service CD.

 

The heater hose connection by the lower engine radiator hose on the water pump.

 

May have a restriction in it that affects heater core performance.

 

Read below-

Edited September 8 by Dean H

[phoenix1151]

OK, thanks all for replies and Dean H for the flow chart.

 

Got to look at the Journey briefly today.  Coolant level still ok from emergency top-up on Thursday.  Codes 0480 & 0481 for cooling fan control circuit 1 & 2 respectively.

 

Didn't think about the vehicle information display at the time, just watched the needle gauge, not that it would have made a difference.

 

Rad fan fuse and low & high relays in the fuse box tested ok.  The A/C has no refrigerant so I pulled the fuse for it a while back, problem?.

 

Ran the engine today while monitoring the dash info display for coolant temp.  It rose steadily to around 105 C which coincided with the needle gauge rising to the middle hash mark like normal.  Does that prove the temp sensor is ok?  Ambient temp indication showed 15 C.  Hose to the rad got hot as expected and the rad fan started!

 

That's all I had time for today after the Grandkids left.  Might try letting it heat up higher tomorrow and see if high speed fan kicks in but that makes me nervous.  What about the resistor/thermistor mounted to the fan housing, how to test it?  

 

1. In an overheating condition, do both 0480 & 0481 codes get posted even if the low speed fan were operating properly?

2. If the rad motor worked for me today on low, excluding the possibility of intermittency somwhere, would that prove the resistor/thermistor is still ok?  

[phoenix1151]

just found this re explaining and testing the resistor.  I'll have to review it later when time allows.

 

https://www.google.com/search?q=journey+rad+fan+resistor+bench+test&rlz=1C1GCEA_enCA886CA886&oq=journey+rad+fan+resistor+bench+test&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIHCAEQIRigATIHCAIQIRigATIHCAMQIRigAdIBCTI1ODkzajBqNKgCALACAQ&sourceid=chrome&ie=UTF-8#fpstate=ive&vld=cid:1d464612,vid:lXnEzK4gtsE,st:366

[phoenix1151]

ok, that was a good video but the Journey resistor N1742001 (68054677AA) only has 2 terminals unlike the one used in the video, so circuit arrangement must be different.  I'll see if I can find an applicable schematic somewhere.

 

Meanwhile, I took the resistor out, measured 0.8-0.9 ohm at ambient temp.  Put the hair dryer on it and got roughly linear variation of ohm with temp (0.5 @ 140F, 0.4 @ 160F, 0.3 @ 170F, 0.2 @ 180F).  So I'm satisfied that the resistor works.  Also satisfied that the fan motor works since it ran yesterday.

 

Oil is fine, not contaminated, so now I'm starting wonder about the water pump and hopefully not a head gasket leak, 🤢 so will have to figure out next step on this old buggy.  

 

PS Dean H : interesting comment re hose blockage affecting heater core performance.  Any corroborating youtube vids that you know of?

Edited September 9 by phoenix1151

[phoenix1151]

Has anyone used one of those block tester kits that test for CO2 in the coolant?  Any recommendations/warnings on particular brands?  If it were to show positive for head gasket leak that would likely be the end of the road for the Journey at this point.  I'm trying to not sink much more money into this old buggy, and neither a water pump nor head gasket replacement is cheap.

[Dean H]

Codes P0480 - P0481 .

Cooling fans 1 and 2 relay control circuit open. 

 

Causes -

-fan Relay

-fan relay control circuit open

-fan relay control circuit shorted to ground. 

 

Your coolant temperature sensor is working fine.

 

Using the digital coolant temperature gauge. You can see when the fan kicks on dropping the temperature.

 

My DJ, fan kicks on at 220 F cools down to 210 F.

 

The analog temperature gauge always stays a hair left of the center line.

 

Thermostat Operation -

 

Rated temperature 195 F.

 

The thermostat is designed to guarantee a minimum engine operating temperature of 88 to 93°C (192 to 199°F). The thermostat also will automatically reach wide open so it will not restrict flow to the radiator as temperature of the coolant rises in hot weather to around 104°C (220°F). Above this temperature the coolant temperature is controlled by the radiator, fan, and ambient temperature, not the thermostat.

 

Fan specifications -

 

Cooling fan wiring diagram -

 

 

The water pump heater hose inlet possible obstruction, is something I read online. Found the piece in the Service CD.  

 

I haven't checked YouTube.

 

 

 

 

 

 

 

 

 

[phoenix1151]

Thanks Dean H, good info.  What is the "fan module - radiator cooling" on the far left of the diagram, what does it do function-wise and where would it be located on the engine?  Since the fan started for me the other day I suspect it would be ok on the wifes Journey though.

 

I ordered a Lisle block tester, it will arrive next week, so I'll check the coolant.

[phoenix1151]

Couldn't edit previous post, so here's a revised version.

 

Thanks Dean H, good info.  I looked up on Mopar site, apparently the whole fan assembly including motor is called "fan module"  Part number 68102116AA, over $500 Cdn.  I see now how the resistor assembly varies the voltage to the "module" when only the low speed relay is energized and that the high speed relay essentially bypasses the resistor assembly altogether sending full voltage to the module. 

 

I expect that the high speed relay is controlled by the ECM but what inputs determine its energization?  My having the A/C fuse out wouldn't be mucking things up would it?  As far as the A/C goes, I think only high refrigerant pressure is what the ECM looks at to kick in high speed???  I pulled the fuse a while ago so the A/C clutch/compressor wouldn't come on since the system lost its refrigerant quite a while ago.

 

I ordered a Lisle block tester, it will arrive next week, so I'll check the coolant.

Edited September 10 by phoenix1151

[Dean H]

First thing for auto parts

go to Rock auto.com. 

 

They have everything you might need at the lowest cost.

You pay a flat fee for shipping from each warehouse your parts come from.

 

I use Rock auto exclusively.

For reference and research as well.

 

https://www.rockauto.com/

 

Your 100% correct regarding the fan operation. 

Only AC high pressure turns the fan on.

 

I found the Fan operation information.

 

Theory of Operation

 

The two speed cooling fan system uses two relays and a radiator fan resistor to control the cooling fan operation. The two relays are the High Fan Relay, Lo-Hi Fan Relay. During low speed mode, the cooling fan operates in series with the Radiator Fan Resistor, limiting the 12 Volt source to the Radiator Fan Module. During high speed mode, the cooling fan motor receives a battery voltage feed directly from the High Speed Radiator Fan Relay.

 

During low speed mode: The PCM grounds the (N201) Fan Relay Control circuit, closing the relay to connect the Cooling Fan 12 Volt Supply circuit to the (N23) Cooling Fan Motor 1 Output circuit. The (N23) Cooling Fan Motor 1 Output circuit supplies 12 Volts to the Radiator Fan Resistor. Current flows through the resistor and out the (N24B) Radiator Fan Relay Output circuit. The current is sent back to the PDC and is spliced into the (N24A) Radiator Fan Relay Output circuit which goes directly to the Radiator Fan Module. The (Z904) Ground circuit provides the ground path for the Radiator Fan Module

 

During High speed mode: The PCM grounds the (N112) Rad Fan Relay Control circuit and the (N112) Fan Relay Control circuit, closing the High Speed Radiator Fan Relay. The Cooling Fan 12 Volt Supply circuit connects to the (N24A) Rad Fan Relay Output circuit and provides 12 Volts to Radiator Fan Module. The (2904) Ground circuit provides the ground for Radiator Fan Module

 

 

 

 

[phoenix1151]

Thanks again Dean H.  Results so far, I'm afraid, are pointing to a head gasket leak, but my block test kit has shipped and I'll give it a test when it arrives, 🤢. 

[phoenix1151]

I conducted an initial block test today, no (major) head gasket leak indicated, a qualified "whew".  I'm not 100% convinced as yet but at least it wasn't a definite bomb.  The engine heated up normally, the tstat opened fine and the rad fan came on, similar to my previous posted temperature.  I moved the tester to the exhaust and after a bit of a delay the fluid did turn yellowish.  I purged the tester with clean air and the fluid went back to blue so the test fluid was ok.  I'll repeat it again in a week or three.

 

I'm not entirely convinced of anything yet.  I'll have to monitor the cold fluid level before/after every trip for a while and see if there is fluid loss and keep an eye on the temp at higher speed (could be the old rad clogging up).  As said previously, we did have a small leak somewhere and added Rislone coolant system sealer and it seemed to work well for a couple of months.  I started checking the fluid frequently thereafter with no fluid loss shown but I got complacent and then this overheating occured.  The amount of coolant I had to add was alarming and this is the first time we've had this trouble.