cjragonese

I have a 2000.
Under normal operation the engine temp sits around 200. After about 45 minutes of city driving Ive noticed while sitting at idle the temp rises to 220 then continues up to around 240 for about a minute or two then drops back to 220. It will do this continuously until I begin driving again and the temp lowers back to 200. Radiator is full. Is this normal? Does anyone know what may be happening? Bad thermostat?

Carman

3sACROWD

You are observing your fans in action. There is nothing wrong with your car. When you're in traffic the fans have to pull air through the radiator. They cycle on and off. Hence the 220 to 240 back to 220. When you're driving, you're forcing air through the radiator at a constant rate and therefore you get better cooling.

pickleseimer

When you say 'around 240', I assume you're watching the temp gauge rather than the DIC water temp numbers. The DIC temp numbers would be more specific than reading the gauge.

The first fan comes on when the coolant temp reaches 226, and stays on until the coolant temp drops to 217. If the temp continues to climb above 226, it will eventually reach a point where additional fan activity will kick in and pull more air through the radiator.

You can prove this for yourself by starting the car and getting it up to temperature. Set the water temp into the DIC, while sitting at idle, pop the hood, get out of the car and wait for the fan to come on which should be as the temp hits 226. Wait for the fan to go off which should be at 217 on the DIC. While sitting at idle, this cycle will repeat itself over and over. If these are the actions you see, your car is functioning correctly.

cjragonese

Good news !! Thank you

old coons

I'm going to have to check this also. The first day I bought my Z a couple months ago, I took a friend out for a ride in Tucson. I wasn't paying attention to the coolant temp, and when we got back to his house antifreeze was pouring on the ground. I started the car back up and turned on the cool-it to cool the car down, it seemed to me that it was above 240 at the time. Since then I have been hitting the cool-it button if it got to 230 or so to get it back down to 200. Something must be wrong with mine if I heat up enough to have coolant overflowing.

lionelhutz

What "cool-it" button? A stock C5 has no such thing...

old coons

It's an aftermarket thing that turns on the fans to cool it. I'm not sure how it works, the previous owner put it in. It does work though.

racebum

when was the radiator changed? on a 2000 you're going to have a TON of debris and scaling present. 10 years imo is max life for a radiator unless it's oversize. cooling efficiency starts to drop. the c5, like the c4 is a vacuum cleaner that sucks up sand and everything else into the fins

in 90deg weather it should never go over 232-234 before the fans go into high speed. this is with the AC off

you can also force the fans on by using the AC which should keep the car under 220 even on the hottest of days if your cooling system is working properly

lionelhutz

Something has been hacked on your car because the fans should come on by themselves as it gets hotter so you don't have to monitor it and manually switch them on.