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On an 85 deg. day in Hold Mode, my 2016 engine temp steadily climbs to 205 deg. then back down to 185, then repeats. Steady 65 mph, few hills, no A/C. Any ideas? Seems like a bad Thermostat.
 

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Even with no AC, the batteries need to be cooled and the AC will turn on without you knowing it. If you turn on fan only, you'll feel when the AC is on (or look at the AC indicator on the center console - at least the G1 shows when it's on).

I wouldn't worry about the temp unless you start creeping up over 280 degrees.
 

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205 is totally normal. When my engine is running anything between 180-220 is normal. I wouldn't worry unless I started seeing it climb over 250
 

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Mine does the same...no worries
 

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As long as it is in 'normal' range, you're ok. There is zero reason to monitor engine temperature on a computer-controlled engine.

Volt has too many accessible data points. Everything from kwh used per charge to engine temp to tire pressure. None of these matter on a minute-by-minute basis. When they are outside 'normal', the computers will tell you via the Driver Information Center (DIC).

Just drive and don't worry about numbers on screens except maybe speed. Even then, speed is not that important unless too low or too high for traffic conditions.
 

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My theory is that the electric drive takes away a lot of the work and heat from the ICE needing to work hard the entire trip. You need some torque? that comes out of the battery pack and much less heat is shed from the ev side of the system. The ICE is going to run cooler than a conventional car. I think that's why the system is cycling temp near the thermostat's closing/opening temp.
 

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My theory is that the electric drive takes away a lot of the work and heat from the ICE needing to work hard the entire trip. You need some torque? that comes out of the battery pack and much less heat is shed from the ev side of the system. The ICE is going to run cooler than a conventional car. I think that's why the system is cycling temp near the thermostat's closing/opening temp.
I think in Hold Mode, the electric motor is not operating at any time. So the temperature cycling is due to the normal functioning of the radiator/fan associated with thee ICE. Thus the ICE runs at the rated temperature for the cooling system. I don't think it runs cooler because of the electric drive. Correct me if I am wrong.
 

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The electric motor is operating all the time in every mode. Very occasionally there is a direct coupling to the engine at certain steady-state speeds but that does not eliminate the electric motors.

I think in Hold Mode, the electric motor is not operating at any time.
 

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The electric motor is operating all the time in every mode. Very occasionally there is a direct coupling to the engine at certain steady-state speeds but that does not eliminate the electric motors.
We're talking about gen2 here, which couples the engine in many more situations that gen1 does. But even gen1 it does this much more than "occasionally", it does it whenever you're in CS mode and above 36mph and not flooring it... which is a lot. You are right that the electric motor(s) are operating all the time in every mode.
 

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The electric motor is operating all the time in every mode. Very occasionally there is a direct coupling to the engine at certain steady-state speeds but that does not eliminate the electric motors.
Thanks, I stand corrected. So in Hold Mode, the ICE is running and powering the electric motor. I wonder if this has any affect on the temperature of the coolant flowing through the radiator? In other words, is the temperature cooler than in a conventional ICE vehicle?
 

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Perfectly normal. The temperature swings are simply a combination of thermostat opening-closing cycles and the effects of cooling fan/vehicle speeds.

The digital temp sensor readout on the Gen2 is creating more issues than it's worth IMO.

It's merely showing what technicians have been observing on scan tools for decades.
WOT
 

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Thanks, I stand corrected. So in Hold Mode, the ICE is running and powering the electric motor. I wonder if this has any affect on the temperature of the coolant flowing through the radiator? In other words, is the temperature cooler than in a conventional ICE vehicle?
your understanding is better now, but not quite there yet. In "hold" mode, the ICE runs when needed to either generate electricity or to help push the car forward or both, it can "power the electric motor", but not always, and that is misleading, its job is to provide energy, which may go into the battery, or be directed electrically to one of the 2 drive motors, or be used in directly pushing the car forward.
 

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To expand on my thought more:

let's say you need 30hp to go 60 mph on a flat road. Well, the engine is rated for 100hp flat out under full load at peak rpm, but I'm saying it barely goes over the 30 hp mark except for longer acceleration runs. Short bursts of performance come from the energy stored in the battery and are recaptured in regen or later, plugging in. The engine didn't have to add too much more- it barely had a chance to change rpm by the time you got done going quickly.

The cooling system does cool the battery and the traction system (electric drive), but those things are shedding way less heat than an internal combustion engine. Anyhow 205 degrees isn't terribly hot or cool. I think the thermostat would be the universal 194F deg GM standard. The other thing that will control the equilibrium point is the temp that the electric fans are programmed to turn on. low 200's are optimal.
 

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your understanding is better now, but not quite there yet. In "hold" mode, the ICE runs when needed to either generate electricity or to help push the car forward or both, it can "power the electric motor", but not always, and that is misleading, its job is to provide energy, which may go into the battery, or be directed electrically to one of the 2 drive motors, or be used in directly pushing the car forward.
I thought in Hold Mode the SOC of the battery remained constant. So if the ICE was also providing electricity to charge the battery, its SOC would increase unless the added charge was later used to power the electric motor to propel the Volt forward. Clearly I need some more education to understand how the Volt works!
 

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What WOT said. I believe 185 degrees has been the standard temp for mechanical thermostat valves to start opening to allow full coolant circulation for many years. You would have a problem of too low of a temp in the engine (and cabin heating) if it was stuck open and too high engine temps if stuck closed. 185 to 205 sounds like perfect temps to me. 205 is not even boiling point of plain water and with the coolant mixture, the boiling point would be much higher so no problem with the temp range.
 

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What WOT said. I believe 185 degrees has been the standard temp for mechanical thermostat valves to start opening to allow full coolant circulation for many years. You would have a problem of too low of a temp in the engine (and cabin heating) if it was stuck open and too high engine temps if stuck closed. 185 to 205 sounds like perfect temps to me. 205 is not even boiling point of plain water and with the coolant mixture, the boiling point would be much higher so no problem with the temp range.
The highest temperature I have observed on the instrument display is 204F; this was after driving about 16 miles on ICE.
 

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. 205 is not even boiling point of plain water and with the coolant mixture, the boiling point would be much higher so no problem with the temp range.
Don't forget that the 16 psi radiator cap will also raise the boiling point even higher. Typically 250-260 degrees F with 50-50 coolant mix.
 

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I thought in Hold Mode the SOC of the battery remained constant. So if the ICE was also providing electricity to charge the battery, its SOC would increase unless the added charge was later used to power the electric motor to propel the Volt forward. Clearly I need some more education to understand how the Volt works!
almost..., whether in hold mode, or at the "bottom" of the active EV mode SOC mode, the Battery state of charge will vary within an (approximate) 5% window, depending on whether the car is going up or down hill, or accelerating, or plowing through head winds or tail winds or truck buffeting. On Gen 1 there is a speed range where at stead speed the generator is putting out its "lowest" efficient output and the car isn't using that much energy so some of it goes into the battery, until the battery reaches to top of its hold mode soc window, and then the car runs off the battery alone to the bottom of the hold mode soc window. I don't know about Gen 2s , but on Gen 1s on level roads, this will happen at stead speeds anywhere below 62 mph or so, (daylight, no wind, no rain etc) There is a constant variation of where power comes from and goes to in the volt, all mostly invisible to the driver. a lot is going on under your right foot...
 
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