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Discussion Starter #1
Hi All,

Looking for advice on what I can say to the service department to have them look in the right direction, because our warranty is up at the end of October, and I want to get this overheating issue resolved under warranty!

About two weeks ago, my wife was driving our 2013 LT (~47.7 k miles) around town for school pick ups, and got the "Engine Hot / AC Off" message. She immediately pulled over, and cut the engine. When she started it up later, it was ok and she kept the heat on just in case, and we took it in on /8/17 for various issues (overheating, AC blowing cool not cold, and some trim/non-warranty issues). They found a leaky compressor coil for the rear AC and fixed that under warranty and told us the overheating was the result of the AC working too hard in combination with the cabin air filter being extremely clogged (never changed was their words, which was another annoyance as we had it in there for the 25k service, and they should have changed it). I'm not really a "car guy" and this seemed like nonsense, but I agreed to change the cabin air filter and keep an eye on it.

Less than a week later, it was overheating again (or close to it, we put the heat on before it got past the last tick mark and hit 260), so we took it in again. They found the water pump was leaking and replaced that under warranty and waived the deductible since we were already in for the same issue.

On the way home from the 2nd attempt to fix the overheating, the needle started creeping up to the 1st tick (~225 max, I'd guess) and when I turned the car off and came back 5 minutes later and turned it over, the temp was up at the last tick mark (~247.5-250)! It came down after a short time.

Yesterday, after the car was parked in sunlight, we were driving in windy roads leaving a park at 20-25 mph on low-grade hills and the temp hit 235-240! Once we got on the freeway, it came down (guessing due to better airflow at 70 mph), but it seems like the issue is still not fixed.

Some additional info as of now:

- coolant level looks good
- radiator from what I can see from the front in between the grill is not too clogged up, some debris but not terrible
- a friend of mine said he thinks it could be a leak between the water jacket and the combustion chamber

Any ideas? I'm going to give them a call tomorrow morning to get a 3rd appointment, but at this point I'm wondering if I should try a different dealer. If there's anything I can say to the service rep to put into the notes for the tech that might steer them towards the right thing to look at, I'd appreciate it!
 

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Discussion Starter #3
Are the radiator fans working? Shouldn't really need them at highway speeds, but "around town," you do.
Thanks for the quick response! I believe so, though they cut off when I turn the car off and I thought before they'd stay on for 15-20 seconds. They were extremely loud before we took it in for the 1st service, but seem quieter now or less likely to be running when I pull into the garage so perhaps they're not working optimally? Is there a good way to test/check other than drive it hard around town for a bit and then stick my head out the window? :)

One other point I should note - a couple of times it's creeped up like that, but come back down near 210 on its own even when driving on side streets but yesterday it was creeping up and hit 235-240 on the side roads during 15-20 minutes of driving before we got on the freeway.
 

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Discussion Starter #4
Are the radiator fans working? Shouldn't really need them at highway speeds, but "around town," you do.
Just turned the car over, then turned the AC on full blast and saw a brief dip in the lights/power as the compressor kicked in, and the radiator fan is definitely blowing.
 

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Is the radiator thermostat was replaced?
 

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Discussion Starter #6
Is the radiator thermostat was replaced?
No, and I'm honestly surprised they didn't do that when they replaced the water pump, since they have to empty the coolant out anyway, right? I guess that's what I'll ask them to try when I take it in again, though the thermostat does seem to work at least partially as the temps do come down, but maybe it's a "lazy thermostat"?
 

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If there was an air pocket I'm sure it would have worked itself out by now. Keep an eye on the overflow tank level.
Other than the thermostat the only thing I can think of is maybe the radiator is full of bugs?
 

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Discussion Starter #8
If there was an air pocket I'm sure it would have worked itself out by now. Keep an eye on the overflow tank level.
Other than the thermostat the only thing I can think of is maybe the radiator is full of bugs?
Yeah overflow level seems stable. I looked through the bumper/grill and didn't see a ton of bugs on the radiator, though there are some. It doesn't look too bad.

So most likely thermostat at this point? I've never seen the temp on this car > 210 before, and when we originally took it in they blamed the weather and said since it's hot it'll run over 210 but as I'd never seen it like that before even in 100+ temps with the AC blasting, it seemed like a load of crap.
 

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Discussion Starter #10
I spoke to the service rep this morning, and they were nice enough to put the tech on the phone (I guess he was nearby). He said he didn't see anything unusual with the thermostat after they replaced the water pump and that they'd let it idle for 45 minutes and normally the temps would go up in those conditions if it were still a problem.

They are also standing firm behind Chevy's policy that anything under 248 is "normal". :/ I said "yes, flooring it uphill in 100 degree weather, but this was 85 degrees and 25 mph steady driving". I doubt it got above 3000 rpms in that 10 minutes of driving when it was up near 235-240.

They are going to do an engine block test to rule out a head gasket leak, but assuming that comes back clean do I just ask them to change the thermostat? They may not do that under warranty I guess, but as the problem hasn't been fixed I am not sure I should have to pay for it nor the deductible I already paid, but I guess that's a battle I'll have to fight with the dealer.
 

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no overheat at 113 with AC blast

My 2016 AWD LTZ 57K has never had an overheating problem, never moves above 210 on the gauge regardless of outside temp in heavy local traffic or 75mph on the freeway at up to 116 this summer in Phoenix AZ. I obviously run the AC all the time. I just came home 113 today driving in local traffic from 25 to 50MPH and completely normal 210 temp. You definitely have something wrong if running 260 temps.
 

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I'll give you my 2 cents,
The problem is the Engine Coolant Temperature Sensor
Or
the connection of the 2 tin plated copper connector pins of the sensor making connection to the wire harness
or wire harness that connects the sensor to the cars computer has a crack in it
, or the connector of the wire harness to the cars computer .....


Let me explain.
The way we measure temperature of radiator coolant in a car, is not with an analog thermometer that you visually look at
But
using an electrical device called a thermistor.
The thermistor is encapsulated in a stainless tube, which is immersed in radiator fluid. It has a plastic connector with two tin plated blades to connect to wire harness.

When the radiator fluid temperature changes,
the resistance of the thermistor changes.
the output current of the resistor, is correlated to temperature
Since the resistance changes with temperature...
the cars computer has a "look up" table , it looks up the resistance, and the resistance is convert to a temperature.
It is called the RT curve, the resistance temperature curve.


The funny thing is, the output current of thermistors at extremes of temperature
Such as very cold and very hot is the same.....
sooooo
if your thermistor had a dead short in it, it could show up as too hot, even though it was too cold
But , a dead short condition would not be intermittent
And a dead short would be easily fixed by replacing the temperature sensor.

You car is telling you it is too hot,
but your car is really NOT TOO hot, it is just that your thermistor circuit has high resistance.
A high resistance condition on the RT look up table
tells your cars computer that the radiator water temperature is dangerously hot.

You are on the right side of the RT curve, with very high resistance.
Your wire harness, the wire connecting to your "thermistor" temperature sensor sometimes has an open condition, like a crack in the wire, a high resistance condition.
or where the harness plugs into the sensor has high contact resistance... ,
tricking the cars computer into thinking it is too hot.

At a minimum, replace the engine coolant sensor, because the terminals of the existing coolant sensor might have high contact resistance, ( zinc migration failure mode)
and
that the tin/lead plating on the NEW terminals of the new sensor might fix your problem.

If that does not fix it then a wire in your wire harness is cracked .
My 2 cents ^^
 

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Discussion Starter #15
I'll give you my 2 cents,
The problem is the Engine Coolant Temperature Sensor
Or
the connection of the 2 tin plated copper connector pins of the sensor making connection to the wire harness
or wire harness that connects the sensor to the cars computer has a crack in it
, or the connector of the wire harness to the cars computer .....
I don't suspect invalid temp readings, because the temp they saw from the ECU was matching an IR gun from what they said.
 

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Discussion Starter #16
What were the results of the head gasket / block test?
All normal, no issues they could find and they claimed they drove it around and let it idle and the temp never went over 209 (though I'd argue idling isn't a real test since the engine wasn't under load).

And sure enough, I plugged in an OBD reader and plotted the temperature driving around town (see attached pic), and I can see it over 210 more often than not and it got up to 240+ at one point, then things opened up and the coolant brought it down but should it be spiking that high on around town driving in 95 degree weather?

I still feel like it's getting hotter than it should...
 

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Wouldn't the scanner be getting the readings from the temp sensor? If it's working but out of range it could give false readings. I would not go by a temp gun reading
A temp sensor is cheap and rather easy to replace. Why not try it?
Stay with an ACdelco sensor. Some cars do not like aftermarket sensors
 

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Discussion Starter #18
Wouldn't the scanner be getting the readings from the temp sensor? If it's working but out of range it could give false readings. I would not go by a temp gun reading
A temp sensor is cheap and rather easy to replace. Why not try it?
Stay with an ACdelco sensor. Some cars do not like aftermarket sensors
Well I guess I could, but it pisses me off that it's under warranty and now I'm paying for stuff like that (along with my time) out of my own pocket. Should I push the dealer to change the sensor and maybe the tstat (maybe it's a "lazy thermostat")?
 

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Make sure you document everything they do and say since it is under warranty and they haven't fixed it yet.
I just want to add another possibility. When was the last oil change, who did it, what kind of oil did they use, and what brand of oil filter did they use? Oil helps cool the engine, it lubricates and carries some heat away too. A blockage somewhere, especially the oil filter may contribute to your issue. Did this happen right after an oil change? Are you due for one? Do it now and see if anything changes.
 

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Yeah overflow level seems stable. I looked through the bumper/grill and didn't see a ton of bugs on the radiator, though there are some. It doesn't look too bad.

So most likely thermostat at this point? I've never seen the temp on this car > 210 before, and when we originally took it in they blamed the weather and said since it's hot it'll run over 210 but as I'd never seen it like that before even in 100+ temps with the AC blasting, it seemed like a load of crap.

.02 Sound like crap to me. I forget the gen 1 setup, but same engine, same low hood profile so I assume similar setup and does not use an overflow tank and there is no overflow level. The plastic tank where you add coolant is actually the upper tank of the radiator itself. Easy to check, examine the cap on the tank, if a snap off plastic lid like the windshield washer tank it is an overflow tank......if it has a hose in and a hose out with a screw on pressure cap usually so labeled .....it is the upper radiator tank and the cap is actually on top of the radiator.



And as with any radiator, if the pressure cap is loose or defective the coolant and engine will overheat.
 
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