C5 Z06------ When driving the car hard the temperatures will go to 240 degrees. Also it will over heat when driving normally with the ac on.
Also when it gets that hot it will blow white smoke. The car has 120,000 miles on it. Have any of you had this problem?
Thanks for your help on this.

 

Sounds to me that you need to do a quick check. Being from Texas (DFW area) I too get the summer heat. The first thing I'd do is check the radiator and condenser on your car. Our Vetts tends to pick up stuff off the road clog the radiator fins. Start there with an inspection. Clean, wipe blow compressed air....etc and you will be shocked (shocked) at how much junks comes out.

My gut says you will be good after that.

 

I agree. A lot of road debris gets lodged at the top of the AC Condenser thus blocking about 1/3 of the air flow through the condenser and the radiator behind it. The longer the period between cleanings the further down the condenser the blockage reaches. Also check the seals between the radiator shroud and the AC condenser and make sure they are in place. If they are blown sideways into the channel to the engine compartment air will blow through the gap and into the engine compartment thus bypassing the cooling system. You have 120K miles on your car I had 12K miles on my car over 20 years ago and had to spend a lot of time cleaning the junk that collected at the top of the condenser. The other thing that can happen is the dirt lodges in the fins of the condenser and you may have to spray water from the rear of the condenser to get dirt out. It used to be a number of forum members who would post designs of home made tools that would let them reach between the radiator and condenser and spray water into the fins from a garden hose.

On a car as old as yours with the miles that it has you may need to inspect the radiator fins to see what kind of condition they are in. Over time the bottom cooling tubes can clog up due to sludge that may have occurred a while ago which can reduce cooling system capacity. You can check that by feeling the back side of the radiator to see where it is hot and where it is cold. If it is blocked it may not be repairable and may need to be replaced. The OEM radiators with the plastic end tanks aren't usually worth repairing Vs replacing.

Bill

 

Thank you both. I will look into cleaning the radiator f[ns I appreciate your help with this matter.

 

I'm no expert, but in my experience white smoke is certainly attributed to a leaking/cracked radiator. Happened to me in the middle of a roadtrip, at the end of a mountain pass coming from Oregon into northern California. Super lucky that within a mile there was a truck stop with jb weld and patch screens. Was able to patch it and make the rest of the trip to San Diego.

I.E. - Check for any cracks or leaks on the radiator itself, and for any lines running to and from.

 

Check the cooling fans.

Here is the description of how the fan system works:

Cooling Fan Control
The engine cooling fan system consists of two electrical cooling fans and three fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage and ignition 1 voltage from the underhood electrical center. The ground path is provided at G102.

During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan 3 relay and the right cooling fan. The result is a series circuit with both fans running at low speed.

During high speed operation the PCM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3-second delay, the PCM supplies a ground path for the cooling fan 2 relay and the cooling fan 3 relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 3 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan 2 relay coil is energized closing the relay contacts and provides battery positive voltage on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed.

The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph).

People are always running around worrying about their temps because they see the numbers on the gauge. These cars are designed to work with high coolant temps and have no problems operating at the temps you indicate. As you can see the fans don't even get turned onto low speed until the temp hits 226 and don't go to high speed until the temp hits 235 degrees. At an autocross where we were running in heats and cycling through the runs quite fast I saw a 242 degree coolant temp on my C5Z for most of an event.

 

White smoke is bad news. Are you burning coolant? Is your coolant inexplicably getting low? You will want to pressure test your (cold) cooling system, and potentially compression test the cylinders, to see if you've got a head gasket leak caused by overheating.

As the weather gets hot we keep getting these threads here. Literally the first thing to do is figure out if your fans are turning on properly, and the second is to clean out the radiator and condenser fins with compressed air. Do that and report back.