plus on hot days the temp on my vette goes to around 224 - 230 when sitting in traffic.
C5 Overheating!
Thread Starter
Team Owner
Joined: Mar 2007
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St. Jude Donor '08-'09-'10-'11
C5 Overheating!
Hi all. I'm new to this forum and need some help. My '99 C5 ragtop is overheating when I am stuck in bumper to bumper traffic. Even long traffic lights are enough to make the gauge climb rapidly. As soon as I start moving again it comes back down to around 200. Is the dealer my only choice here? Is there a known problem? I'm not losing any fluid. Any help you all can give is appreciated. 
Race Director
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From: West Norriton PA
St. Jude Donor '08
Hi all. I'm new to this forum and need some help. My '99 C5 ragtop is overheating when I am stuck in bumper to bumper traffic. Even long traffic lights are enough to make the gauge climb rapidly. As soon as I start moving again it comes back down to around 200. Is the dealer my only choice here? Is there a known problem? I'm not losing any fluid. Any help you all can give is appreciated.
Team Owner
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From: Plano Texas
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St. Jude Donor '07-'08-'09-'10-'11-'12-'13
As noted by ajg1915, check the FRONT of the radiator (at the top).
Also, verify your fans are coming on.
The issue (hot at a standstill) is NOT unusual. Some adjustment (I.e., cooler thermo, program the fans to come on 'earlier') are possible remedies.
Also, verify your fans are coming on.
The issue (hot at a standstill) is NOT unusual. Some adjustment (I.e., cooler thermo, program the fans to come on 'earlier') are possible remedies.
Safety Car
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From: Rochester MN
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St. Jude Donor '04-'05-'06-'07
NCM Ambassador
I know this sounds strange, but if you car is warming up, turn the AC on. This forces the fans on...
This will not fix the cause of the overheating, just keeps things from boiling over
This will not fix the cause of the overheating, just keeps things from boiling over
Last edited by ptdrummer54; Mar 27, 2007 at 01:40 PM.
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St. Jude Donor '05-'06
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Ed
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Burning Brakes
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From: Las Cruces New Mexico
I had the same problem last year. I agree with above, make sure there is not a plastic bag, lots of leaves or other type of junk between the radiator and the ac cooler. It is very easy to take the radiator shroud off and look between the two "radiators". Use a water hose to blast debris through the fins or even compressed air. You will find a lot of little sticks and rocks come out. In fact I did mine again last week before driving across Texas. I did not have a single problem with the temperature rising above 200 while sitting in San Antonio traffic. Also make sure the fluid level in the tank is at the proper level and replace as neccessary. Good luck.
Safety Car
Joined: Jun 2000
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From: Conroe TX
St. Jude Donor '11
If your outside temperatures are over 20 degrees F, then use 30% antifreeze and 70% water. Water dissapates heat much better than antifreeze. Also add a bottle or two of water wetter to the antifreeze and water.
As others have said, 220 to 230 is not uncommon or harmful to the LS1.
As others have said, 220 to 230 is not uncommon or harmful to the LS1.
Tech Contributor
Joined: Dec 2006
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From: Van Buren Arkansas
Wounded Warrior Escort '11
I too was having similar issues a long while back. I cleaned out a large amount of rocks from the AC Condenser fins which sits in front of the radiator. I did it using a long neck and curved air-gun. When I was done, I had quite a pile of tiny rocks there... a lot more than I thought was possible. Ran nice and cool/normal temps after that.
Burning Brakes
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From: South of Indy
St. Jude Donor '07-'08
Uh-Huh
I recently bought an 02 coupe and after I loaded it on my car hauler, when I leaned under to hook up the tie downs, there was a large plastic bag up in the air intake area right in front of the radiator/tranny cooler. I can see how this could happen easily, but the seller was a bit embarassed it was in there and he hadn't found it. Pays to take a peak in there after each road trip.
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St. Jude Donor '07-'08-'09-'10-'11-'12-'13
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From: South Windham CT
Hi all. I'm new to this forum and need some help. My '99 C5 ragtop is overheating when I am stuck in bumper to bumper traffic. Even long traffic lights are enough to make the gauge climb rapidly. As soon as I start moving again it comes back down to around 200. Is the dealer my only choice here? Is there a known problem? I'm not losing any fluid. Any help you all can give is appreciated.
Melting Slicks
Joined: Feb 2002
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From: Indianapolis In
I agree!!! If mytemp goes over 210, I just turn on the A/C & taadaa back around 200.
Safety Car
Joined: Oct 2000
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From: Monticello MN
While this is true, you may want to consider having the radiator cleaned, also. If this has never been done, it may help. I had a friend whose C5 was overheating and all it took was a thorough cleaning of the radiator fins, from the engine side out, and all was cool again. He had tried a thermostat and it did nothing.
Ed
Ed
Ed
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From: The line waiting to see Santa Claus stretched all the way back to Terre Haute, and I was at the end, Indiana
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16-'17-'18
Had the same problem last summer. The car would seriously overheat in slow or stopped traffic. I looked under the front and the radiator looked clear. I spoke with several knowledgeable people and they all insisted that part of the radiator was blocked...it only takes a small percentage. Found out that you have to jack the front of the car up and stick your head WAAAAAY up behind the shroud to see the top of the radiator. There it was a small Wal-Mart plastic bag (about 8"x10") up where you couldn't see it. Removed it and a few handfulls of leaves and grass...no more overheating.
Safety Car
Joined: Mar 2006
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From: Godfrey IL
All good advice. The biggest culprit is the crap up in the radiator.
This is the first vehicle I've ever had that deposits bugs on the garage floor regularly.
They fall from the very top of the ac cooling coils as the engine cools down.
You think the spiders would go up there when I get home and have a hot meal.
This is the first vehicle I've ever had that deposits bugs on the garage floor regularly.
They fall from the very top of the ac cooling coils as the engine cools down.
You think the spiders would go up there when I get home and have a hot meal.