2004 Z06

After driving around town for a while one beautiful evening when it was about 80 degrees F, I noticed that the engine temp was over 220 and as high as 235. I tried to keep the revs up to cool it down. Would there be a DIC code shown if one or both of the fans were not operating? Any suggestions why the engine is running so hot. Coolant is full and stock coolant. Stat is stock 195 degree F.

I live where it is relatively dry and the ambient temperature rarely gets over 90.

Thanks

 

check your thermostat; could be sticking. Pull it and boil it. Watch for the diaphram to open. If you have a thermometer, use it to determine what temp it opens, if at all. Should be around 195-200.
Good luck!

 

i removed the plastic shroud that hangs below the from of the car as it was extremely damaged, tems ran much higher without this deflecting air up to the radiator, ensure its present and in good condition.
check that a trash bag or crap hasnt worked its way up to block your radiator.
i also switched to a different oil and my temps ran much higher, i switched back and now temps are back to normal.
arizona here with a/c and vert top off my temps will fluctuate greatly expecially in traffic, with a/c on temp is almost always 193 unless i follow traffic closely and no air gets to the radiator.
alos watch your oil temp mine is mostly 210ish unless im working the engine, this is reguarless of a/c or other variables.
if your oil temp stays steady reguardless of water temp, they i dont think i would worry too much.

 

It's probably either a stuck thermostat (esp. if it started happening abruptly if you drive the car often), low coolant or the fans not coming on....Do what everybody else has said with boiling the thermostat and report back.

 

Thanks, fellows.

Will let you know what happens.

 

This is actually normal fyi. The 2nd fan is not programmed to come on until 220degrees stock. This is done to help control emissions among a couple other things. [mine does the same thing]

Its really of no concern unless it continues to climb. Even if you sit in traffic you should hear the 2nd fan come on and see it creep back down.

Great mod is to get a 160 or 180 degree thermostat and have the fans programmed to come on sooner.

 

Mine was doing the same thing in slow traffic last year. I took it to the Dealer, and they said it was normal. As long as it cools down on the highway under 200°, then there is nothing wrong. If it doesn't, then you have a clogged A/C condensor, and maybe radiator. But the AC catches the bulk of the dirt and crap.
I have read that GM does this to pass emmisions, which is why they went to Mobil One Synthetic oil.

 

From your description, I'd say your fans are operating properly. The fans first come on, essentially at half speed (running in series), at 226 degrees. If the temp keeps rising, usually because you're driving in stop and go traffic on a hot day, the fans go to full speed (running in parallel) at 235 degrees. If the A/C is on and you are driving at less than 35 mph, the fans run at the half-speed rate to assist with cooling. At highway speeds, temp should be between appx 192 and 196 degrees.

You likely have dirt, bugs, paper, or whatever blocking some of the airflow. This will cause higher temps, everything else being equal. Your first order of business should be to check and, if necessary, clean the "trash" from the A/C condenser and the radiator.

Hope this helps,
Ernie

 

After having the same situation with my '99, I asked about this at the dealer. Apparently they have two fans, and come on at different times. The second one comes on at 235 degrees. Apparently they want them to run that hot, although I'm not used to it.

 

Everything posted in response is true. Assuming you are driving around with the windows down you probably have the A/C off. Just turn it on and manually set it to low speed. This will keep the fans on and you s/n/h any temps above 200ish.

 

Right on. I have experienced cooling woes over the years. I had a Tstat fail which sucked. Temps of 250 on the highway is not good. -- replaced it with a 180 tstat. In my tuning I then turned the fans on earlier...that helped a bit...but they were bandaids for the real problem. Finally, I pulled the radiator shroud and pulled the fans and radiator out of the car and pulled a lot of rocks and debris from it- Sadly, my AC condenser was also full... an hour of hosing and 2 hours of compressed air and they were clean... been running at 190 to 210 ever since.

 

A stuck thrmostat almost always results in a pegged temperature gauge. What you have is NOT because of a stuck thermostat. The temp should reach 235 but come down once the fan turns on. Our temperature gauges are very sensitive, so 200-235 on hot days is not uncommon.

 

Thanks, again fellows. Very helpful. I was driving around town with the A/C off when this happened. I turned the A/C on and the temp drops to approximately 195. Need to re-program the fans if that is possible to be able to drive around with the windows down and the A/C off and have temps below 200.

 

Didn't mention in my earlier post, but I have lowered my fan temps to turn on at 210 degrees and 220 degrees instead of the stock settings of 226 and 235. I use a stock thermostat and those settings seem to be just about right. (By the way, off temps are 201 and 211.)

Some of the ways to accomplish this are: 1) you can add an external fan controller, 2) you can have a professional tuner change the temps to whatever you wish, or 3) you can buy a handheld tuner (or a complete tuning software package) and change fan temps and a few other things yourself. I chose the latter. Because my car pings fairly regularly on our California 91 octane gasoline, I wanted to retard the timing a few degrees along with the fan change. The Diablo Sport Predator allowed me to do both. Do a few searches and you'll find plenty of info on this stuff.

Ernie

 

black04 is the only one here that I have seen thus far to correctly describe the operation of the stock C5 engine cooling fan system. Both fans have a low and high speed and both operate together at either the low or high speed. It is NOT a case where one fan comes on first at one certain temp and then the then the second fan comes on at a higher temp. All this is covered in the GM Corvette Service Manual in the Engine section, under Cooling System Description and Operation.

The engine cooling fan system consists of two electrical cooling fans and 3 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.

For model years 2001 through 2004, the PCM operates (commands) the 2 fans together as follows:

The low speed is commanded on when the coolant temperature reaches 226 degrees F. It is turned off when the coolant temperature lowers to 219 degrees F. The High speed is commanded on when the coolant temperature reaches 235 degrees F. It is turned off if the coolant temperature lowers to 226 degrees F. When the A/C is on and the coolant temperature reaches 185 degrees F, the low speed will be turned on when vehicle speeds are less than 35 mph.

For earlier model years, the stock fan temp set points are slightly different.

HTH. :yesnod

BTW, nice job Ernie