Overheating issue on my LS3
Thread Starter
Race Director
Joined: Apr 2005
Posts: 11,138
Likes: 11
From: Fremont CA
St. Jude Donor '06-'07-'08-'09-'10-'11-'12-'13-'14-'15-'16-'17-'18-'19-'20
NCM Sinkhole Donor
Overheating issue on my LS3
Yes, I have a C5, but I thought I would tap the LS3 guys for info...
OK, I've got an LS3 in my C5 and although I put in a new thermostat (twice), a new water pump, and a new dual-core aluminum radiator, I am running around 230 on the freeway under load. When it is idle, it quickly cools to 200-210. Flat freeway is low 220's. Any heavy acceleration or going up even a slight hill and it jumps to 230-235. The one time I let it hit redline, it started steaming, so I know the temp sensor is accurately assessing the temperature. Also, when I just start the car and watch it warm up, both fans ARE kicking on around 180 (approx).
It has been suggested that there may be air pockets. Can anyone give me the best way(s) to make SURE I get rid of any remaining air pockets?
Other ideas on what could be causing the problem?
The car is not throwing any codes.
OK, I've got an LS3 in my C5 and although I put in a new thermostat (twice), a new water pump, and a new dual-core aluminum radiator, I am running around 230 on the freeway under load. When it is idle, it quickly cools to 200-210. Flat freeway is low 220's. Any heavy acceleration or going up even a slight hill and it jumps to 230-235. The one time I let it hit redline, it started steaming, so I know the temp sensor is accurately assessing the temperature. Also, when I just start the car and watch it warm up, both fans ARE kicking on around 180 (approx).
It has been suggested that there may be air pockets. Can anyone give me the best way(s) to make SURE I get rid of any remaining air pockets?
Other ideas on what could be causing the problem?
The car is not throwing any codes.
Drifting
Joined: Apr 2010
Posts: 1,443
Likes: 7
From: Bristol raceway area
Is the front air dam (all 3 pieces ) there and intact? Evil-Twin has said how important this is at speed to keep temps down.
When i changed the coolant and added a 160 stat on our '02 over a year ago, i followed the info. about removing all the air from the system and it went great.
I put a 160 stat in our '09 LS3 last year and the system just about bled itself of air. Easy.
There is a hose in front of drivers side head you can unhook to make sure coolant is coming out. Some people say to remove rad. cap and blow, just don't swallow any coolant!
When i changed the coolant and added a 160 stat on our '02 over a year ago, i followed the info. about removing all the air from the system and it went great.
I put a 160 stat in our '09 LS3 last year and the system just about bled itself of air. Easy.
There is a hose in front of drivers side head you can unhook to make sure coolant is coming out. Some people say to remove rad. cap and blow, just don't swallow any coolant!
Thread Starter
Race Director
Joined: Apr 2005
Posts: 11,138
Likes: 11
From: Fremont CA
St. Jude Donor '06-'07-'08-'09-'10-'11-'12-'13-'14-'15-'16-'17-'18-'19-'20
NCM Sinkhole Donor
Is the front air dam (all 3 pieces ) there and intact? Evil-Twin has said how important this is at speed to keep temps down.
When i changed the coolant and added a 160 stat on our '02 over a year ago, i followed the info. about removing all the air from the system and it went great.
I put a 160 stat in our '09 LS3 last year and the system just about bled itself of air. Easy.
There is a hose in front of drivers side head you can unhook to make sure coolant is coming out. Some people say to remove rad. cap and blow, just don't swallow any coolant!
When i changed the coolant and added a 160 stat on our '02 over a year ago, i followed the info. about removing all the air from the system and it went great.
I put a 160 stat in our '09 LS3 last year and the system just about bled itself of air. Easy.
There is a hose in front of drivers side head you can unhook to make sure coolant is coming out. Some people say to remove rad. cap and blow, just don't swallow any coolant!
One other thing, my car is SUPER lowered. Don't know if that could effect air flow enough at speed?
Safety Car
Joined: Jul 2009
Posts: 3,755
Likes: 190
From: Baton Rouge LA
St. Jude Donor '14, '16
I would think you are dealing with air bubbles, or not enough water in your water/coolant mix. You could also try some water wetter, but considering the temps you are experiencing, something is reducing the specific heat capacity of your coolant mix (air is probably the biggest culprit).
This post:
http://forums.corvetteforum.com/1574721422-post3.html
seems to offer a good purging methodology.
This post:
http://forums.corvetteforum.com/1574721422-post3.html
seems to offer a good purging methodology.
Last edited by sevinn; Mar 1, 2011 at 03:54 PM.
Burning Brakes
Joined: Jun 2008
Posts: 1,214
Likes: 3
From: CA
When I installed my Dewitts radiator and EWP I had a similar problem with temps. On the fwy I would get these sudden spikes in temp that would go up to 23X degrees. It would sometimes happen when I was getting up to speed or just stepping on it a few times.
What I did was turn the heater on for about 10-15mins while the car was idling. At the same time I would add coolant/water mix to the car. After pooring in coolant I would squeeze both coolant hoses (the bottom and top hoses) several times. This would help pumps water and also to let me know if there was any coolant flowing thru.
If you have a manual water pump you might want to bring the revs up to 2500 sometimes to put more pressure in the system.
Also, one thing I would also do is put my mouth on the reservoir tank and blow in it. This would also help move the fluid thru.
My car now stays @ around 175 degrees on the fwy. These may not be the factory procedures but it worked for me.
What I did was turn the heater on for about 10-15mins while the car was idling. At the same time I would add coolant/water mix to the car. After pooring in coolant I would squeeze both coolant hoses (the bottom and top hoses) several times. This would help pumps water and also to let me know if there was any coolant flowing thru.
If you have a manual water pump you might want to bring the revs up to 2500 sometimes to put more pressure in the system.
Also, one thing I would also do is put my mouth on the reservoir tank and blow in it. This would also help move the fluid thru.
My car now stays @ around 175 degrees on the fwy. These may not be the factory procedures but it worked for me.
Burning Brakes
Joined: Jul 2008
Posts: 923
Likes: 37
From: Green Bay Wisconsin
Hello,
Make sure your fans are not running backwards, a simple wiring error would have them running backwards and would cause the car to over heat.
"the simplest explanation is most likely the correct one". Occam's razor
Douglas in Green Bay
Make sure your fans are not running backwards, a simple wiring error would have them running backwards and would cause the car to over heat.
"the simplest explanation is most likely the correct one". Occam's razor
Douglas in Green Bay
Yes, I have a C5, but I thought I would tap the LS3 guys for info...
OK, I've got an LS3 in my C5 and although I put in a new thermostat (twice), a new water pump, and a new dual-core aluminum radiator, I am running around 230 on the freeway under load. When it is idle, it quickly cools to 200-210. Flat freeway is low 220's. Any heavy acceleration or going up even a slight hill and it jumps to 230-235. The one time I let it hit redline, it started steaming, so I know the temp sensor is accurately assessing the temperature. Also, when I just start the car and watch it warm up, both fans ARE kicking on around 180 (approx).
It has been suggested that there may be air pockets. Can anyone give me the best way(s) to make SURE I get rid of any remaining air pockets?
Other ideas on what could be causing the problem?
The car is not throwing any codes.
OK, I've got an LS3 in my C5 and although I put in a new thermostat (twice), a new water pump, and a new dual-core aluminum radiator, I am running around 230 on the freeway under load. When it is idle, it quickly cools to 200-210. Flat freeway is low 220's. Any heavy acceleration or going up even a slight hill and it jumps to 230-235. The one time I let it hit redline, it started steaming, so I know the temp sensor is accurately assessing the temperature. Also, when I just start the car and watch it warm up, both fans ARE kicking on around 180 (approx).
It has been suggested that there may be air pockets. Can anyone give me the best way(s) to make SURE I get rid of any remaining air pockets?
Other ideas on what could be causing the problem?
The car is not throwing any codes.
Thread Starter
Race Director
Joined: Apr 2005
Posts: 11,138
Likes: 11
From: Fremont CA
St. Jude Donor '06-'07-'08-'09-'10-'11-'12-'13-'14-'15-'16-'17-'18-'19-'20
NCM Sinkhole Donor
I ran the car all summer with no issues and never touched the fans. Then the problem suddenly started. However, my wife just reminded me that a few weeks before the overheating began, the car came up with a low coolant warning. We added 50/50 and thought nothing of it. I wonder if when the coolant was low if it could have sucked air in frombthe empty overflow tank?
Tech Contributor
Joined: Dec 2006
Posts: 10,962
Likes: 29
From: Van Buren Arkansas
Wounded Warrior Escort '11
Well, purge the air first and make sure you look and smell for coolant leaks. When you shut it down, the hoses should be pressurized and if not, then something isn't right.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
Thread Starter
Race Director
Joined: Apr 2005
Posts: 11,138
Likes: 11
From: Fremont CA
St. Jude Donor '06-'07-'08-'09-'10-'11-'12-'13-'14-'15-'16-'17-'18-'19-'20
NCM Sinkhole Donor
Looks like it was an airflow issue with the car being so low. The new airdams were deflecting air rather than directing it to the radiator. Once I installed the Big Mouth Airdam my freeway temps dropped 30 degrees. 
Cruising
Joined: Apr 2011
Posts: 12
Likes: 0
I just had this same problem after replacing my t-stat...exactly the same!! Make sure your on level ground and not leaning with coolant tank on low side of tilt if any at all. Jack the corner of car where the coolant tank is making it the highest point in system and run and bleed air out. Worked for me, hopefully you as well. Let me know if it helped...Good Luck
