Engine Temp
Thread Starter
Intermediate
Joined: Jun 2021
Posts: 41
Likes: 5
Engine Temp
Almost have the new insulation and carpet down, but the 76' runs warm by the floor pans. 50mph plus stays under 200, but if I'm driving around for a while and sit for more than 5 minutes at idle the engine temp get closer to that 260. I have the shroud around the radiator and the fan is running at least it is when I start it up. Could the radiator have anything to do with that? ...wondering if I should take it over to the jiffy lube to have it flushed?
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
If you are going to own a Vette, you need to learn how do the basic jobs to maintain it. A coolant flush is very easy.
And after watching a couple YouTube vids on scam auto shops, J.L. would be the last place I would go. But its your money / car.
Just about all C3s did run hot at the floorboards. Why? Because the heater core refuses to shut off. Why? Because some engineer thought it would be ideal to have the heater core shut-off, vacuum operated.
So your first job after the flooring is to install a heater core shut-off valve (NAPA $25) Put it inline of the 3/4" hose going to the core. Open it in the fall. Close it in the spring.
Your overheating at idle is a air circulation issue. (Overheating at speed, is a coolant circulation issue)
Check foam seals around the Rad. Belts tight? Clutch Fan operation, etc.
Think "air" or lack of it. What's blocking or diverting the air?
And after watching a couple YouTube vids on scam auto shops, J.L. would be the last place I would go. But its your money / car.
Just about all C3s did run hot at the floorboards. Why? Because the heater core refuses to shut off. Why? Because some engineer thought it would be ideal to have the heater core shut-off, vacuum operated.
So your first job after the flooring is to install a heater core shut-off valve (NAPA $25) Put it inline of the 3/4" hose going to the core. Open it in the fall. Close it in the spring.
Your overheating at idle is a air circulation issue. (Overheating at speed, is a coolant circulation issue)
Check foam seals around the Rad. Belts tight? Clutch Fan operation, etc.
Think "air" or lack of it. What's blocking or diverting the air?
Last edited by HeadsU.P.; Sep 21, 2021 at 03:39 PM.
Safety Car
Joined: Jun 2017
Posts: 4,786
Likes: 425
From: North Georgia, USA
The thread title is "Engine temp", but the discussion seems to be about interior temp at the floor.
If engine temp is an issue, especially if it's cooler at highway speeds and warmer at idle, test your fan clutch.
Safety warning: When doing this test, be sure to keep your fingers, beard, hair and any other body parts you've grown attached to out of the moving belts and spinning pulleys.
Easy fan clutch test. Get the thin cardboard tube from a roll of paper towels. After driving for a while (engine up to operating temperature), park the thing, let it sit idling but not moving for a minute or two. Watch the temp gauge, don't let it overheat. Then open the hood. Very carefully, holding one end of the cardboard tube, press the other end of the tube against the back side of the spinning fan. If you can stop the fan with the cardboard tube, the fan clutch is shot.
Although the older fan clutches did last a long time, modern ones are pretty short lived. It's now strongly recommended that the fan clutch be replaced at the same time the water pump is replaced. Both have a similar service life now, and a failure in either one can take out the other one.
If engine temp is an issue, especially if it's cooler at highway speeds and warmer at idle, test your fan clutch.
Safety warning: When doing this test, be sure to keep your fingers, beard, hair and any other body parts you've grown attached to out of the moving belts and spinning pulleys.
Easy fan clutch test. Get the thin cardboard tube from a roll of paper towels. After driving for a while (engine up to operating temperature), park the thing, let it sit idling but not moving for a minute or two. Watch the temp gauge, don't let it overheat. Then open the hood. Very carefully, holding one end of the cardboard tube, press the other end of the tube against the back side of the spinning fan. If you can stop the fan with the cardboard tube, the fan clutch is shot.
Although the older fan clutches did last a long time, modern ones are pretty short lived. It's now strongly recommended that the fan clutch be replaced at the same time the water pump is replaced. Both have a similar service life now, and a failure in either one can take out the other one.
Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
First thing I would do is get an IR meter to verify the exact temp of the coolant to verify the dash gauge is accurate as well as check the into and out of temps of the coolant going through the radiator.If the temp gauge checks out then the temp differential of the coolant going into and out of the radiator will give you some clue as to whether it needs flushed. Next would be the fan clutch and the seals around the radiator as well as ignition timing(are you running the factory smog timing or the settings suggested on this forum including manifold vacuum for the distributor vacuum advance).
Shutting off the coolant circulation through the heater core will help with the interior heat ( I used a vacuum operated valve for this so I can open and close it using the centre console controls). Is the foam collar in place to reduce hot air from the motor getting blown along the transmission tunnel?
Shutting off the coolant circulation through the heater core will help with the interior heat ( I used a vacuum operated valve for this so I can open and close it using the centre console controls). Is the foam collar in place to reduce hot air from the motor getting blown along the transmission tunnel?
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Race Director
Joined: Mar 2017
Posts: 11,905
Likes: 4,478
From: Virginia
First thing I would do is get an IR meter to verify the exact temp of the coolant to verify the dash gauge is accurate as well as check the into and out of temps of the coolant going through the radiator.If the temp gauge checks out then the temp differential of the coolant going into and out of the radiator will give you some clue as to whether it needs flushed. Next would be the fan clutch and the seals around the radiator as well as ignition timing(are you running the factory smog timing or the settings suggested on this forum including manifold vacuum for the distributor vacuum advance).
Shutting off the coolant circulation through the heater core will help with the interior heat ( I used a vacuum operated valve for this so I can open and close it using the centre console controls). Is the foam collar in place to reduce hot air from the motor getting blown along the transmission tunnel?
Shutting off the coolant circulation through the heater core will help with the interior heat ( I used a vacuum operated valve for this so I can open and close it using the centre console controls). Is the foam collar in place to reduce hot air from the motor getting blown along the transmission tunnel?
Please post some photos! DIY coolant flush isn't too hard, if you can get under the car. The block plugs are easy to reach with the exhaust removed.
Here's a link to the foam horse collar, with a diagram.
https://www.zip-corvette.com/68-79-s...on-collar.html
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,062
From: altered state
St. Jude Donor '05
I bet a flush will help; learned on bottom feeder cars to remove the fan once a yr and from the backside with a garden hose blow all the crap out of the fins makes a huge difference.
May want to look into an aftermarket alum. radiator, they are not as much as they once were and totally worth it.
May want to look into an aftermarket alum. radiator, they are not as much as they once were and totally worth it.
Pro
Joined: Jul 2021
Posts: 719
Likes: 156
don't futz around w/ just a flush ... CLEAN IT ... look for CF member noonie posts about GM CLEAN procedure.
https://www.corvetteforum.com/forums...car-yet-2.html
https://www.corvetteforum.com/forums...car-yet-2.html
Dr. Detroit
Joined: Mar 2012
Posts: 10,095
Likes: 4,022
From: New Braunfels Texas
Check your fan clutch......
I had my 98 Mustang GT flushed at Jiffy Lube once.....the **** was brown in the system. I watched them do it......they have a powerful vacuum that sucks every last bit of the old **** out of the system.....they used a treatment chemical....ran the car and did the suction thing again.....filled with green and distilled that I brought them. $100. It was worth it to me as I didn't want to do it......
Of course, YRMV......the flush at Jiffy Lube is exactly as good as the person running it......just know what you are getting before hand....
Jebby
I had my 98 Mustang GT flushed at Jiffy Lube once.....the **** was brown in the system. I watched them do it......they have a powerful vacuum that sucks every last bit of the old **** out of the system.....they used a treatment chemical....ran the car and did the suction thing again.....filled with green and distilled that I brought them. $100. It was worth it to me as I didn't want to do it......
Of course, YRMV......the flush at Jiffy Lube is exactly as good as the person running it......just know what you are getting before hand....
Jebby
Last edited by Jebbysan; Sep 24, 2021 at 07:13 AM.
Melting Slicks
Joined: Feb 2017
Posts: 3,232
Likes: 1,232
From: PHX AZ
Buy Service manual
AIM manual
Wiring diagram
Vacuum diagram.
Fundamental knowledge is key here.
Personally, I WISH to hear/see the following words...
I've read the service manual
I looked at all the cooling system diagrams.
And finally 'we're talking about ENGINE TEMPS not floor temps.'
Yes, in a way they ARE related; To whit
When the fan is barely operating most of the VERY hot air is going under the car...heating up the tranny tunnel and floors. When the fan is pulling the proper amount of CFM's the engine temp and floor temp will go down.
Fix the cooling issue and the floor temp will follow.
AIM manual
Wiring diagram
Vacuum diagram.
Fundamental knowledge is key here.
Personally, I WISH to hear/see the following words...
I've read the service manual
I looked at all the cooling system diagrams.
And finally 'we're talking about ENGINE TEMPS not floor temps.'
Yes, in a way they ARE related; To whit
When the fan is barely operating most of the VERY hot air is going under the car...heating up the tranny tunnel and floors. When the fan is pulling the proper amount of CFM's the engine temp and floor temp will go down.
Fix the cooling issue and the floor temp will follow.
Melting Slicks
Joined: Feb 2018
Posts: 2,319
Likes: 720
From: Marietta GA
I took my 2001 Camaro to a radiator shop and they used compressed air (with water) to really get the crud out of the OEM Radiator. That was the best $ 70 I ever spent, way better than a garden hose and bottle of radiator cleaner. They also fixed the leak and pressure tested the OEM radiator on my 73 SB, a lot cheaper than a replacement. A large part of their business centers around trucks/specialized equipment, where replacement radiators are not easy to find.
Dr. Detroit
Joined: Mar 2012
Posts: 10,095
Likes: 4,022
From: New Braunfels Texas
I just want to add that EGT's are the #1 cause of interior heat on a C2-C3 Corvette.......incorrect timing specs can send EGT's 300-400 degrees higher than normal and where is the exhaust? Where does that heat go....?
It also effects coolant temps.......
So to the OP......where is your timing set at?
Jebby
It also effects coolant temps.......
So to the OP......where is your timing set at?
Jebby
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,062
From: altered state
St. Jude Donor '05
Had Jiffy Lube flush a radiator on an 87 G20 van I figued it was worth a shot
There was so much crap that came out I could not believ eit...guy did a great job and yes it was worth it
ran the bejeezus out of that during hot Ca summer months as a work vehicle it never ran warm . Could they sprout a leak maybe this one didnt
edit: ditto on the garden hose/can of secret sauce you pour in its kind of a waste. Those machines they use are super effective.
There was so much crap that came out I could not believ eit...guy did a great job and yes it was worth it
ran the bejeezus out of that during hot Ca summer months as a work vehicle it never ran warm . Could they sprout a leak maybe this one didnt
edit: ditto on the garden hose/can of secret sauce you pour in its kind of a waste. Those machines they use are super effective.
Last edited by cv67; Sep 25, 2021 at 02:27 PM.
Thread Starter
Intermediate
Joined: Jun 2021
Posts: 41
Likes: 5
Great advice, I am turning the wrenches and learning quite a bit, I know enough to have moderate success. ...not setup to change out all the fluid, so in this case easier to pay extra to have it flushed. Thank you for the tip, putting the valve on the list. Appreciate the time you took to respond.
