Running hot
Thread Starter
1st Gear
Joined: Aug 2021
Posts: 1
Likes: 0
From: Little Rock
Running hot
Hello, I am new to this forum and hope to get some help with my 79 corvette. It seems to run hot. I have changed the thermostat and flushed the radiator. I also changed the sending unit to make sure it was working properly. After a 20 minute drive in 90 degree weather the fluid in the reservoir is boiling. My next step will be to replace the radiator but I’m not sure if it needs to be changed. Any suggestions/comments?
Le Mans Master
Joined: Jun 2019
Posts: 7,658
Likes: 2,470
From: Indiana
Yes
i suggest copius pictures especially around radiator and fan seals your car details, manual auto, any mods etc…
also where your timing is at..
overheating how? When? Pic of front lower spolier..
i suggest copius pictures especially around radiator and fan seals your car details, manual auto, any mods etc…
also where your timing is at..
overheating how? When? Pic of front lower spolier..
Last edited by interpon; Aug 29, 2021 at 08:42 AM.
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,221
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From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
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It just may be needing a new radiator cap. What is the temp gauge running at. I second the call for pictures. Make sure you have a full fan shroud and you need all the seals around the radiator and from the front air dam up to the radiator as Interpon said.
Race Director
Joined: Mar 2017
Posts: 11,953
Likes: 4,510
From: Virginia
Low hanging fruit: Have you confirmed the temperature with an IR thermometer shot at the upper radiator hose? What is your timing set to? Can you squeeze the lower radiator hose and confirm that the spring is there to keep it from collapsing?
Photos will help us help you, and years from now will help other people searching the Forum.
Photos will help us help you, and years from now will help other people searching the Forum.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
First, I will give you the basics on your issue, then maybe you can narrow it down.
Overheating at speed is a Coolant Circulation issue.
Overheating at idle is a Air Circulation issue.
What do these mean? If you are traveling at 60-70 MPH then obviously you are getting plenty of air. But the coolant system can't keep up. Why?
Could be restricted block / head passages, collapsed lower radiator hose, faulty W.P, bad thermo, etc, etc.
If you are standing still, the waterpump and hoses are likely keeping up, good water circulation etc. But you have loss of cooling with not enough air through the radiator. Why?
Once a yr, take a compressed air wand or air gun and blow air backwards, through the Rad. Lots of crap lodged in the fins.
Then you have all the foam seals around the Rad to contend with. Is the clutch fan working? Fan belts tight? Shroud in place?
What is your gauge reading, by the way?
Overheating at speed is a Coolant Circulation issue.
Overheating at idle is a Air Circulation issue.
What do these mean? If you are traveling at 60-70 MPH then obviously you are getting plenty of air. But the coolant system can't keep up. Why?
Could be restricted block / head passages, collapsed lower radiator hose, faulty W.P, bad thermo, etc, etc.
If you are standing still, the waterpump and hoses are likely keeping up, good water circulation etc. But you have loss of cooling with not enough air through the radiator. Why?
Once a yr, take a compressed air wand or air gun and blow air backwards, through the Rad. Lots of crap lodged in the fins.
Then you have all the foam seals around the Rad to contend with. Is the clutch fan working? Fan belts tight? Shroud in place?
What is your gauge reading, by the way?
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
one air flow detail that is the exception to Heads Up's rule. the chin spoiler. it is needed to push air up into the area in front of the radiator. without it most air just blows under the car. your 20 minute drive: around town, lights and traffic? or 20 minutes on the highway at speed? and when it gets warm, if you get up to speed do you see temp drop almost immediately? or is it staying hot at 60 mph?
Last edited by derekderek; Aug 29, 2021 at 10:14 AM.
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,391
From: At my Bar drinking and wrenching in Lafayette Colorado
Timing is the greatest contributor to hot-run issues. If you do not have enough initial timing, and if you are not running vacuum advance correctly hooked up, your engine will run hot. Check and fix your timing before chasing other tails.
Lars
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