[C2] Engine overheating
Drifting
Joined: Sep 2024
Posts: 1,552
Likes: 1,008
From: Florida
Le Mans Master
Joined: Jan 2000
Posts: 6,298
Likes: 416
From: Michigan
You said you wanted to upgrade the radiator but you never said what was in the car now. The original radiator for all mid-year small blocks was an aluminum radiator 3155316. (Dewitts #941) Anything other than this is a downgrade. DeWitt's direct fit model number 1249063M is a nice replacement model. If you have a brass/copper replacement radiator, I would remove it and get one of the above models. With that said, the stop and go overheating is typically related to the vacuum advance as others have mentioned. It's pretty easy to test whether the vacuum can is working or not. With a timing light connected, attaching the vacuum hose to the vacuum can should result in a jump in timing and RPM. If you don't see any action then the vacuum can is probably dead. You need this additional timing at idle to prevent overheating at low RPM.
Last edited by Tom DeWitt; Mar 20, 2026 at 07:51 PM.
Race Director
Joined: Feb 2007
Posts: 15,408
Likes: 8,839
From: northern california
C2 of Year Finalist (track prepared) 2019
Pro
Joined: Feb 1999
Posts: 683
Likes: 113
From: Strongsville, Ohio
Drifting
Joined: Sep 2024
Posts: 1,552
Likes: 1,008
From: Florida
I know of 2 newer cars ( 30 years ago) that were having overheating issues while on the freeway only.. Owners took the car to the dealer ( on warranty) who replaced the fan clutches and the problem went away..
Race Director
Joined: Feb 2007
Posts: 15,408
Likes: 8,839
From: northern california
C2 of Year Finalist (track prepared) 2019
I'm not sure I buy the lack of airflow theory, though. There is nothing preventing air from flowing thru the radiator. Too, whatever flow resistance is presented by the fan blades would seem to be the same whether they are stationary or rotating.
My hunch is that replacing the fan clutches on those cars merely covered up the real problem.
Safety Car
Joined: Jul 2022
Posts: 3,956
Likes: 1,604
From: Eastern MA
I'm confused as well, because it 'de-clutches' at operating temp (not just freeway speeds) although it never really free spins, it's like 20%
And if it's fully engaged all the time, the engine is roaring like a propeller driven airplane
I can sorta-kinda envision an electronically controlled fan clutch causing problems at speed as the car's brains get the wrong data and do things based on that wrong data...but this Sting Ray in question seems immune to that effect
And if it's fully engaged all the time, the engine is roaring like a propeller driven airplane
I can sorta-kinda envision an electronically controlled fan clutch causing problems at speed as the car's brains get the wrong data and do things based on that wrong data...but this Sting Ray in question seems immune to that effect
Le Mans Master
Joined: Nov 2015
Posts: 7,419
Likes: 2,594
From: Really Central IL Illinois
I can almost believe they will overheat on the freeway with a bad fan as the radiator on the newer cars is woefully small. It amazes me how they cool even with the electric fans running full blast. If the fan stops, it becomes a restriction on air flow. Just a guess.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
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
Drifting
Joined: Sep 2024
Posts: 1,552
Likes: 1,008
From: Florida
I am adding this for all of the " confused " on here...... One of the repairs was done to my sales managers car.... To be honest I thought that didn't make sense either, but he never had another overheating event with his car for the years we worked together.... I asked him about it frequently. ( being a car guy)....
So if this " was not the correct repair" replacing the declutching fan unit sure seemed to solve the problem on his car.... Had to think back and this would of been late 80's.....
So if this " was not the correct repair" replacing the declutching fan unit sure seemed to solve the problem on his car.... Had to think back and this would of been late 80's.....
Last edited by Limp; Mar 22, 2026 at 08:20 AM.
Drifting
Joined: Sep 2024
Posts: 1,552
Likes: 1,008
From: Florida
Intermediate
Joined: May 2024
Posts: 36
Likes: 75
From: Wisconsin fox valley area
I had vacuum canister on distributor go bad last fall and had in city running hot at times issues do to it was sucking air in thru canister made it lean and a little too much timing.
Capped vacuum port off and took a degree of timing out and it cooled off
Capped vacuum port off and took a degree of timing out and it cooled off
Le Mans Master
Joined: Jan 2000
Posts: 6,298
Likes: 416
From: Michigan
Le Mans Master
Joined: Jan 2000
Posts: 6,298
Likes: 416
From: Michigan
Drifting
Joined: Jun 2006
Posts: 1,595
Likes: 180
From: Durham ON
Thread Starter
3rd Gear
Joined: Mar 2026
Posts: 3
Likes: 0
From: Bonita Springs, Florida
I have taken all suggestions posted here which were greatly appreciated and my mechanics are checking every suggestion out to see what works.
We took out the old radiator and are installing a new "DeWitts Direct-Fit Pro Series Radiator" with a single black aluminum fan.
Also installed a new water pump and reservoir, and all new hoses throughout the engine compartment. Checked timing as well.
We'll see what hapens.
Thanks again for all the suggestions......much appreciated !
We took out the old radiator and are installing a new "DeWitts Direct-Fit Pro Series Radiator" with a single black aluminum fan.
Also installed a new water pump and reservoir, and all new hoses throughout the engine compartment. Checked timing as well.
We'll see what hapens.
Thanks again for all the suggestions......much appreciated !
Tech Contributor
Joined: Jan 2007
Posts: 19,392
Likes: 1,135
From: Dyer, IN
I have taken all suggestions posted here which were greatly appreciated and my mechanics are checking every suggestion out to see what works.
We took out the old radiator and are installing a new "DeWitts Direct-Fit Pro Series Radiator" with a single black aluminum fan.
Also installed a new water pump and reservoir, and all new hoses throughout the engine compartment. Checked timing as well.
We'll see what hapens.
Thanks again for all the suggestions......much appreciated !
We took out the old radiator and are installing a new "DeWitts Direct-Fit Pro Series Radiator" with a single black aluminum fan.
Also installed a new water pump and reservoir, and all new hoses throughout the engine compartment. Checked timing as well.
We'll see what hapens.
Thanks again for all the suggestions......much appreciated !
