Overheating over 55 MPH
Thread Starter
7th Gear
Joined: Jun 2014
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Overheating over 55 MPH
I have a C# 1977 Corvette with a dewitts alum radiator with twin fans NO FAN ON ENGINE, It overheats with A/C on only, in city temp is fine about 190 with a 180 t stat. 5.7 liter 20 0ver with 10 to 1 flat tops 268 cam alum heads. Can anyone help
Last edited by Kevin F; Aug 30, 2015 at 12:25 PM.
Melting Slicks
Joined: Jul 2006
Posts: 2,291
Likes: 492
From: Salmon Arm, BC
Check to see that the lower air dam is in place...it diverts the air up into the rad.....it's common to be missing. Make sure all the foam seals are in place around the rad. Check to make sure the front of the rad is clean,use a vacuum to clean it out. Is there a shroud around the rad as well as the electric fans? If not the corner parts of your rad aren't doing all they could be towards cooling.
Thread Starter
7th Gear
Joined: Jun 2014
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Air Dam? is that the spoiler done mean to sound stupit my first Corvette Does not have the gaskets around radiator and shroud is not in place fans came as a kit with radiator didn't know I still had to run shroud
Check to see that the lower air dam is in place...it diverts the air up into the rad.....it's common to be missing. Make sure all the foam seals are in place around the rad. Check to make sure the front of the rad is clean,use a vacuum to clean it out. Is there a shroud around the rad as well as the electric fans? If not the corner parts of your rad aren't doing all they could be towards cooling.
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
Sigh, another electric fan and overheating story. Are the twin fans enclosed in a large shroud that covers the whole face of the radiator? If not only a small portion of your radiator is doing any cooling. The original radiator used a large fan shroud for a reason so taking that shroud off and not using an equivalent shroud is a huge mistake.
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
At highway speeds the fan is doing very little for cooling "if"; the lower air dam is in place, the seals around the radiator are in place and the seal from the core support to the hood. Basically seal it up so any air up front has to be forced through the radiator and does not go around it.
Check timing also, retarded timing will make it run hot.
Check timing also, retarded timing will make it run hot.
Racer
Joined: Mar 2008
Posts: 487
Likes: 48
From: Ocala Florida
Not sure that I have a "remedy" per se for your overheating. However, if the dual fans you have came with the DeWitts radiator you will not need any further sealing around the radiator. When I installed mine I had already purchased the sealing kit but could not see how it would fit properly so I call DeWitts. Tom himself told me that it was not necessary since the dual fan setup I had covered the entire span of the aluminum radiator and for me he was correct. I didn't use any of the sealing foam kit and mine never runs over 180. While there are always purists that curse the electric fan scenerio the fact is that if it were that bad all of the newer cars would still be running a mechanical fan with a fan belt. There are other things to check to see why you are running hot but according to DeWitts it isn't due to the packing around the radiator.
Thread Starter
7th Gear
Joined: Jun 2014
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Thread Starter
7th Gear
Joined: Jun 2014
Posts: 7
Likes: 0
At highway speeds the fan is doing very little for cooling "if"; the lower air dam is in place, the seals around the radiator are in place and the seal from the core support to the hood. Basically seal it up so any air up front has to be forced through the radiator and does not go around it.
Check timing also, retarded timing will make it run hot.
Check timing also, retarded timing will make it run hot.
Melting Slicks
Joined: Jul 2006
Posts: 2,291
Likes: 492
From: Salmon Arm, BC
is this the setup you have? If so you shoud be fine, the problem is probably the spoiler/air dam.
http://cdn.shopify.com/s/files/1/016...g?v=1357674939
this is the Airdam/Spoiler
https://www.paragoncorvette.com/imag...large/7445.jpg
http://cdn.shopify.com/s/files/1/016...g?v=1357674939
this is the Airdam/Spoiler
https://www.paragoncorvette.com/imag...large/7445.jpg
Last edited by OMF; Aug 30, 2015 at 05:52 PM.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
I had a slight problem when I first got my 69. Never overheated, just got warmer than I like when I was on the highway. Pulled the front license plate bracket and now it never sees 200*. No a/c, BB, 12.5 compression and plenty of timing with real good gas.
You may be required to run a front plate- Technically I am too, but running year of manufacture plates, most of the LEO's that would know are long since retired..
Someone said check the seals around your radiator- good advice. Also check the top of the radiator between it and the core support. I had a 77 and used a piece of a pool noodle to seal it up.
You may be required to run a front plate- Technically I am too, but running year of manufacture plates, most of the LEO's that would know are long since retired..
Someone said check the seals around your radiator- good advice. Also check the top of the radiator between it and the core support. I had a 77 and used a piece of a pool noodle to seal it up.
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
HI Tim,.....the OP needs to drill about 3 3/16 holes in the flange of the stat.....because to make up for the smaller diameter of the modern stats.....a 180 stat opens at 180 ok but the flow is restricted to the 'NEW' standard diameter smaller opening....typical EPA......
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
HI Tim,.....the OP needs to drill about 3 3/16 holes in the flange of the stat.....because to make up for the smaller diameter of the modern stats.....a 180 stat opens at 180 ok but the flow is restricted to the 'NEW' standard diameter smaller opening....typical EPA......
And the goofy C3 myths continue..........................
Thread Starter
7th Gear
Joined: Jun 2014
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I got to the problem seems like only when the A/C is running its runs hot checked my pressures 215 head all seals around radiator is new and new air dam once I turn the A/C off you can eatch the temp drop 180 t stat both fans run with the A/C on