2005 C6 Z51 - 45,000 miles. Can anyone tell me the "normal" coolant temperature. Noticed that on a 65 degree day, coolant temperature will reach 220 degrees. No evidence of overheating, no coolant leaks and fan appears to be operating properly.

 

Only time the coolant in my C6 gets that hot is if I'm in a line of cars at the drive-up window for takeout.

Around town, in moderate stop and go, it'll hit 205. Most of the time, it'll run 198 to 203.

Just realized you're talking about having the Z51 option package. Don't know if that matters or not. My C6 doesn't have it.

 

Temp will vary from 190 to 220 or higher depending on whether or not the car is moving and what the ambient temps are. 220 for a car not moving fast (traffic) is OK. If you were driving 60 mph for 15 or 20 minutes at those ambient temps and getting 220 degrees then I would say the cooling system needs some work. Usually the fans are turned off above 35 mph because they limit air flow.

From the Service Manual:
Cooling Fan Control - Variable Speed Single Fan System
The engine cooling fan is a variable speed fan. The engine control module (ECM) controls the fan speed by sending a pulse width modulated signal to the cooling fan control module. The cooling fan control module varies the voltage drop across the cooling fan motor in relation to the pulse width modulated signal.

Cooling fan speed is effected by many different conditions and can be adjusted from 10 percent to 90 percent duty cycle (PWM), 90 percent is considered high speed fan. When multiple cooling fan speed requests are received the ECM uses the highest cooling fan speed of all the requests. The ECM commands the cooling fan ON under the following conditions:

• Cooling fan duty cycle starts when engine coolant temperature reaches approximately 95°C (204°F) and reaches high speed at temperatures above 113°C (235°F).

• Cooling fan duty cycle starts when A/C pressure reaches approximately 1100 kPa (160 psi) and reaches high speed at A/C pressures above 2480 kPa (360 psi).

• At engine oil temperatures above approximately 150°C (302°F) the cooling fan duty cycle will be commanded to high speed.

• At transmission oil temperatures above approximately 132°C (270°F) the cooling fan duty cycle will be commanded to high speed.

• After the vehicle is shut OFF if the engine coolant temperature at key-off is greater than 113°C (235°F) or the A/C pressure is greater than 1720 kPa (249 psi) the cooling fan duty cycle is set to 50 percent, low speed. If the coolant temperature drops below 110°C (230°F) and the A/C pressure drops below 1660 kPa (241 psi) the fan will shut OFF. The fans will automatically shut OFF after 2 min. regardless of coolant temperature.

Low Coolant Message
The engine cooling system utilizes an algorithm based low coolant level system which eliminates the need for the coolant level sensor previously positioned inside the surge tank. The algorithm measures the difference in engine coolant temperature readings over time as a function of engine speed, to determine if the cooling system has a low coolant condition. After vehicle start up, the engine control module (ECM) sends an engine RPM and engine coolant temperature message through the body control module (BCM) to the HVAC control module. The HVAC control module uses engine coolant temperature and engine RPM to determine if an increase in engine coolant temperature is due to a low coolant level condition. This system is capable of losing 2 full liters of coolant before triggering the Low Coolant indicator. Because the surge tank holds approximately 0.8 liters when filled to the proper level, its possible that the Low Coolant indicator will not be triggered, even though the surge tank is completely dry.

Engine Coolant Indicator(s)
COOLANT OVER TEMP
The IPC illuminates the COOLANT OVER TEMP indicator in the message center when the following occurs:

• The PCM detects that the engine coolant temperature exceeds 124°C (256°F). The IPC receives a class 2 message from the PCM indicating the high coolant temperature.

• The IPC will also illuminate the CHECK GAGES indicator and a chime sounds when this condition exists.


Bill

 

200 +/- 20 degrees is fine

When moving it should go below 200, in traffic it can go above 200.

 

 

THANKS!! I think I am OK. Temp drops to 195+/- at freeway speeds.

 

It should never drop much below that (even in winter) if the thermostat is functioning properly. Having said that, oil temperature can be as low as 140+ in winter if your car has an air oil-cooler (vs coolant oil-cooler/heater), like all GSs and ZO6s prior to 2012, I believe.

 

That is normal for stock thermostat and stock fan settings . No worries .

 

I would do a coolant flush if it hasn't ever been done yet, just to be sure you have all fresh stuff in there.
After 45k+ miles and 8+ years it's probably time, regardless of how long the owner's manual and/or the Dexcool label says you can leave it in there for.

 

Bingo...you're fine.

 

I have been reading this thread looking for a hint...My 2006 seems to run a little hot on the highway. In town I have seen my temps get up to 230...on the highway it will run between 210 and 225. Now, granted, the ambient air temp has been in the 100 degree area and I have been running the A/C, but I don't think it should be running this hot. The car has 100,700 miles on it and I replaced the water pump this past April at about 93,000 miles. I just need to know if I need to take it in and have the dealer look at it.

 

2005 owner's manual says once every 5 years.

 

One last comment look for debris in front of the radiator.
(Ingested from the bottom of the car above the front lower plastic air dam)

 

If it hasn't been flushed since new it is 3 years overdue. Dexcool seems to do well at the 5 year/100K interval GM recommends. I have been following that recommendation on all of my family's vehicles since 97. So far three of them are on their second 5 year change. One of those is coming up on its 3rd 5 year change. One is coming up on its first 5 year change later this month. Only one of those cars had a cooling system failure in all of that time and that failure was due to a broken inlet line on a plastic coolant reservoir.

Bill