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Discussion Starter · #1 ·
So she's a 2006 300C
Never had any issues with her and only done regular maintenance (brakes, tires, oil change, etc.)
She's at exactly 99,911 miles as of driving to work this morning.
I've had her since she was new.

About a year ago (fall 2011) she started to randomly overheat.
Didn't matter if I was driving down the road at 80 or sitting in traffic.
The temporary solution was to shift to neutral and floor it. She would rev-limit at 4K and after a few seconds (2-4) she would drop the temp back down.
let off the gas and she ran fine for a while. sometimes just minutes other times days.
I figured it was thermostat so I had that replaced... She ran good for about a month or so then started overheating again.
Do the mechanic recommended another thermostat in case I got a bad one.
We replaced it again and same thing... ran good for a month then started up again. Still she would get hot on occasion (we're talking a few times a week, give or take).
So I had them pull the thermostat and leave it out (summer time).
She did it again after a couple weeks... now we know what it's NOT!
I then bought and replaced the water pump and thermostat with Mopar parts from dealership (I bought them myself).
Dumped all coolant and poured new in it. We watched her run for a while and push all the bubbles out into the overflow and topped her off.
She ran good for two+ months.
This morning... SAME THING!
I did the 3x key turn and no codes come up. No check engine light... nothing.

Ideas?
It's about time for a good tune up anyways so I figured if I'm going to have any major work done it's the best situation if ever there was one.

My friend recommended to have them look into a blown head gasket.
 

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BLOODY ADMENSTRUATOR
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It's weird that you aren't seeing any codes. They gotta be there, somewhere.

Have you run a pressure test on the cooling system?

Before thinking head gasket - you might want to find a good service dept with a good electronics tech to plug in the StarScan and get a diagnosis . . .

Hopefully - others with far better tech knowledge than me will chime in here.
 

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The powertrain control module (PCM) has been programmed to monitor certain cooling system components:

If the engine has remained cool for too long a period, such as with a stuck open thermostat, a Diagnostic Trouble Code (DTC) can be set.

If an open or shorted condition has developed in the relay circuit controlling the electric radiator fan, a Diagnostic Trouble Code (DTC) can be set.

If the problem is sensed in a monitored circuit often enough to indicated an actual problem, a DTC is stored. The DTC will be stored in the PCM memory for eventual display to the service technician.

It really could be a whole host of different things that can cause a high temp reading. Some things to check for:
Is the temperature gauge reading correctly?
Is the temperature warning illuminating unnecessarily?
Coolant low in coolant reserve/overflow tank and radiator? Check for coolant leaks and repair as necessary.
Pressure cap not installed tightly. If cap is loose, boiling point of coolant will be lowered.
Poor seals at the radiator cap. Check condition of cap and cap seals. Replace cap if necessary.
Check condition of radiator filler neck or degas bottle. If neck is bent or damaged, replace radiator or degas bottle.
Coolant level low in radiator but not in coolant reserve/overflow tank. This means the radiator is not drawing coolant from the coolant reserve/overflow tank as the engine cools. Check condition of radiator cap and cap seals.
Check condition of radiator filler neck. If neck is bent or damaged, replace radiator.
Check condition of the hose from the radiator to the coolant tank. It should fit tight at both ends without any kinks or tears. Replace hose if necessary.
Check coolant reserve/overflow tank and tanks hoses for blockage.
Incorrect coolant concentration?
Coolant not flowing through system. Check for coolant flow at radiator filler neck with some coolant removed, engine warm and thermostat open. Coolant should be observed flowing through radiator. If flow is not observed, determine area of obstruction and repair as necessary.
Radiator or A/C condenser fins are dirty or clogged. Remove insects and debris.
Radiator core is corroded or plugged. Have radiator re-cored or replaced.
Dragging brakes. Check and correct as necessary.
Fuel or ignition system problems.
Bug screen or cardboard is reducing airflow. Remove bug screen or cardboard.
Thermostat partially or completely shut. Check thermostat operation and replace as necessary.
Cooling fan(s) not operating properly. Check cooling fan drive operation.
Cylinder head gasket leaking. Check for cylinder head gasket leaks.
Heater core failure.

Good luck on getting this issue resolved!
 

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Discussion Starter · #5 ·
I am shying away from it being a thermostat issue. We removed the thermostat for a few months during this summer and she did it even then. So I thought it might be the pump going bad and that's when I replace the pump and thermostat (Both with brand new Mopar parts from dealership).
The overflow seems to be doing it's job and there doesn't seem to be any blockage there. It's so sporadic and inconsistent that I'm thinking it almost MUST be electrical or a sensor.
Tonight I'm going to pop the hood and verify that both fans are turning and they kick on appropriately.
after that then I'm thinking temp sensor ($30 part and easily replaced) might be my best bet to start with if the fans appear to be working properly.
 

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That ^^^^ sounds like a good plan. I wonder why the dealer didn't test the sensor? Or maybe no result could be given as its so random. I'd check the wiring harness and plug at the sensor as well.
 

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deanoalf

I am shying away from it being a thermostat issue. We removed the thermostat for a few months during this summer and she did it even then. So I thought it might be the pump going bad and that's when I replace the pump and thermostat (Both with brand new Mopar parts from dealership).
The overflow seems to be doing it's job and there doesn't seem to be any blockage there. It's so sporadic and inconsistent that I'm thinking it almost MUST be electrical or a sensor.
Tonight I'm going to pop the hood and verify that both fans are turning and they kick on appropriately.
after that then I'm thinking temp sensor ($30 part and easily replaced) might be my best bet to start with if the fans appear to be working properly.
could you smell coolant when the car was reading it was hot
 

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So she's a 2006 300C
Never had any issues with her and only done regular maintenance (brakes, tires, oil change, etc.)
She's at exactly 99,911 miles as of driving to work this morning.
I've had her since she was new.

About a year ago (fall 2011) she started to randomly overheat.
Didn't matter if I was driving down the road at 80 or sitting in traffic.
The temporary solution was to shift to neutral and floor it. She would rev-limit at 4K and after a few seconds (2-4) she would drop the temp back down.
let off the gas and she ran fine for a while. sometimes just minutes other times days.
I figured it was thermostat so I had that replaced... She ran good for about a month or so then started overheating again.
Do the mechanic recommended another thermostat in case I got a bad one.
We replaced it again and same thing... ran good for a month then started up again. Still she would get hot on occasion (we're talking a few times a week, give or take).
So I had them pull the thermostat and leave it out (summer time).
She did it again after a couple weeks... now we know what it's NOT!
I then bought and replaced the water pump and thermostat with Mopar parts from dealership (I bought them myself).
Dumped all coolant and poured new in it. We watched her run for a while and push all the bubbles out into the overflow and topped her off.
She ran good for two+ months.
This morning... SAME THING!
I did the 3x key turn and no codes come up. No check engine light... nothing.

Ideas?
It's about time for a good tune up anyways so I figured if I'm going to have any major work done it's the best situation if ever there was one.

My friend recommended to have them look into a blown head gasket.
Hi there, Was this issue ever resolved, and if so what was the final diagnosis. If you don't mind me asking.
 

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My 2005 C (83K miles) overheated last week. It had been acting up for about a year, but last week the high temperature light came on for the first time. Upon returning home I saw that the fans weren't running. I did some electrical testing and, to my mind, after some resistance testing of the fan circuit (open circuit down to the fans by themselves),and applying an alternate 12-volt power source directly to the fans, I have concluded that both fans have died. I have booked the car into the stealership after the 4th of July holiday for replacement of the fan motors. They quoted $184 for the job. They will have to drop my catch can from the front of the engine to allow for tilting the fan assembly back so as to be able to lift it out.

I am having the passenger airbag recall done during the same visit.

I will report back here after the jobs are done.
 

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Okay now, I'm back with an update.

Dropped the car off at 8 this A.M. for the passenger air bag recall and replacement of the cooling fan motors.

The service manager ,with whom I had discussed things, turns out to be on vacation this week.

At about 10 A.M I get a call questioning the all-in price of $184 given to me by the service manager. And informing me that because they did not diagnose the problem, I would have to pre-pay for the motors. The service manager never mentioned that in our discussion either. And the all-in price was wrong as Chrysler fan motors go for more than $100 EACH!Then I got some story about the service manager having been told (apparently by stealership management) not to quote prices! SAY WHAT!

Anyway, the parts guy thinks the service manager must have quoted using NAPA motor prices. He will be getting back to me as to whether they can do the job with NAPA motors.

I am going to call about whether/when the airbag recall will be done.

And then relieve them of the fan replacement job, and all other future connection with me.
 

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FINAL UPDATE:

Just picked up the car after the passenger air bag was replaced under the recall. All appears to be well except for a greasy smudge on the right side of the dash.

As for the radiator cooling fan replacement: I fired the stealership. I went on-line and ordered the complete fan assembly for less than $100 delivered from RockAuto after I talked to some guy at the stealership who said he talked to the on-vacation service manager who told him the problem was the speed control resistor of the cabin ventilation fan. I called 'BULLSHIT' and enlightened the guy with the knowledge that the car is a 300C and uses an electronic module, not a resistor, for the cabin ventilation fan speed control. AND we're talking radiator cooling fans here, not the cabin ventilation fan.

As Joe Pesci's character in the movie 'My Cousin Vinney' says after questioning some witnesses: "I'm done with this guy!"
 

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The replacement fan assembly from RockAuto delivered today. Planning to change it out on Sunday when the weather chills.
 

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The replacement fan assembly from RockAuto delivered today. Planning to change it out on Sunday when the weather chills.
I was wondering if you ever got the car fixed with the cooling fans. I have a 1999 Chrylser 300M that I have had the same issues with for the last 2 years after $7,000.00 worth of work. We have replaced sensors, radiator, caps, flushed and filled, replaced the reservoir overflow box, new radiator, new hoses, replaced the fuel rails based on a TSB bulletin, New water pump, timing chains, thermostats (3 times). Not sure what else to change but to push her to the junk yard. I do know this overheating is still happening and she runs as smooth as can be..let her sit for about 15 months, just starting as necessary to keep things working, still got the over heating problem but she drives like a dream, no other issues. I need serious help before I just junk her and let my money go. Have a 17 year old that we were trying to fix it to let drive.

Oh I should mention that the bull crap stories I get from repair shops haven't helped either, been to 4 different shops, 2 dealerships and yet to figure out what's wrong...don't trust a whole lot of people..

Help in Dayton, OH
 

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I was wondering if you ever got the car fixed with the cooling fans. I have a 1999 Chrylser 300M that I have had the same issues with for the last 2 years after $7,000.00 worth of work. We have replaced sensors, radiator, caps, flushed and filled, replaced the reservoir overflow box, new radiator, new hoses, replaced the fuel rails based on a TSB bulletin, New water pump, timing chains, thermostats (3 times). Not sure what else to change but to push her to the junk yard. I do know this overheating is still happening and she runs as smooth as can be..let her sit for about 15 months, just starting as necessary to keep things working, still got the over heating problem but she drives like a dream, no other issues. I need serious help before I just junk her and let my money go. Have a 17 year old that we were trying to fix it to let drive.

Oh I should mention that the bull crap stories I get from repair shops haven't helped either, been to 4 different shops, 2 dealerships and yet to figure out what's wrong...don't trust a whole lot of people..

Help in Dayton, OH
Well, to start with I am not familiar with the 300M model so I can only speak generally.
You have not indicated that you (or anyone else for that matter) have ever observed the operation (or non-operation) of the engine cooling fan(s) when the engine was overheating. Based on all that you have reported as having been done to unsuccessfully solve your problem, and if the fan(s) do not ever operate, I'd say the fan(s) themselves are toast.
Get them replaced and go from there.
And best wishes!
 

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My '07 C 5.7 Hemi started to overheat. No codes. Replaced the thermostat, checked the hoses, upper and lower, all good. Checked the water pump, and it's good. Pulley isn't loose, no leaks detected. However, facing the engine, on the left, just behind the radiator is a puddle on the plastic pan beneath the engine. Fresh oil change with Royal Purple and K&N oil filter, CAI filter is clean. I have to replace the coolant every other day. Temp goes up to 200+ after driving about 2 miles. Leak can not be found by me or my mechanic. Searching with a black light and dye in the coolant around the engine and radiator yields no results. ????
 

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My '07 C 5.7 Hemi started to overheat. No codes. Replaced the thermostat, checked the hoses, upper and lower, all good. Checked the water pump, and it's good. Pulley isn't loose, no leaks detected. However, facing the engine, on the left, just behind the radiator is a puddle on the plastic pan beneath the engine. Fresh oil change with Royal Purple and K&N oil filter, CAI filter is clean. I have to replace the coolant every other day. Temp goes up to 200+ after driving about 2 miles. Leak can not be found by me or my mechanic. Searching with a black light and dye in the coolant around the engine and radiator yields no results. ????
You might get a better response by starting a new thread instead of piggybacking onto this four-year-old one.

If you and/or your mechanic are pumping the system up to pressure or running it to come up to pressure and there is no leak, there's only one other place the coolant could be going, and that's into the combustion chamber. You could try a combustion gas leak test.

But the fact that there's coolant in your splash pan tells me there's a leak, whether you and/or your mechanic can find it or not. Some of the more common failure areas are hairline cracks in the plastic radiator tanks and the coolant reservoir. There is also a plastic coolant T on the rear of the engine that tends to get brittle and crack, especially as it ages.

Exactly what kind of coolant is in there?
 
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