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Another cooling question (1/14)
 1/24/23 5:30pm
Corvette33
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Hi all , my stock 75 L48 is running cool and when I bring it to operating temperature it’s  (165) ..all of my insulation around radiator is correct, and I installed a new thermostat (180) and still running cool . I also put thermal gun on and this is what I got . I did plug up vacuum hose to heat riser would that effect it ? Any help would be appreciated thanks

upper rad hose -165                          

Thermostat housing-165

lower rad hose-120

upper neck on rad -180 



|UPDATED|1/24/2023 4:30:43 PM (AZT)|/UPDATED|
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Re: Another cooling question (2/14)
 1/24/23 5:35pm
73shark
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Overland Park, KS - USA

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1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


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I once read where the thermostat tolerance was +/- 20%.

You can check the tolerance of your temperature gun by pointing it at the side of a saucepan that contains boiling water.

Out of curiosity, what is your instrument panel temperature gauge say?



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Re: Another cooling question (3/14)
 1/24/23 5:38pm
Corvette33
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Right at 160

Re: Another cooling question (4/14)
 1/24/23 6:11pm
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


Joined: 7/9/2003
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If your temp gun proves to be accurate, then I'd try another t-stat.



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Re: Another cooling question (5/14)
 1/24/23 6:42pm
Corvette33
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Maybe a 195

Re: Another cooling question (6/14)
 1/24/23 8:48pm
Adams' AppleLifetime Member
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#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


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Is that the temps you see while driving it, or just sitting? Can't say I've ever heard of a '68-'82 car running too cool....😮 Changing the t-stat opening temp will only change the temp that the stat opens to allow full coolant flow. Once open, the t-stat no longer has any real control over engine temp. Engine temp(after stat opening) is mostly controlled by coolant flow thru the radiator(water pump), and air flow thru the radiator(fan). Another often overlooked contributor to engine temp is ignition timing. Severely retarded timing will cause high cylinder temps, as will extreme advanced timing. If it is actually running 160 deg while driving, I would add a few degrees of timing.....it'll prolly run a little better too.

What are the ambient temps when you are checking the coolant temps?



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Re: Another cooling question (7/14)
 1/24/23 10:50pm
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


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A car thermostat does control the engine coolant temperature. It opens and closes to regulate the temperature within a tolerance band of the temperature on the thermostat. It's just like the thermostat in your house where it controls the temperature set on it.

The radiator's function is to remove heat from the coolant. And the water pump then circulates the coolant to the degree that the thermostat allows it to. In the winter time the thermostat will just barely open to maintain the required temperature of the coolant in the engine block.

I had a thermostat that I found to be stuck open about 1/16" and the car would never get warm in the winter time.

 



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Re: Another cooling question (8/14)
 1/25/23 7:44am
Corvette33
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The outside temp was about 50 in New York however was running cool in warmer temps as well 

Re: Another cooling question (9/14)
 1/25/23 7:49am
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Driving also 160-165 

Re: Another cooling question (10/14)
 1/25/23 7:52am
Corvette33
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Ok possibly a defective stat I’ll try a new one and keep you updated  thank you 73 shark 

Re: Another cooling question (11/14)
 1/25/23 9:25pm
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73shark said:

A car thermostat does control the engine coolant temperature.

Agree to disagree on that. 🙂

 In the real world, once the t-stat opens, it stays open as long as the engine is running. In my experience, if the cooling system is full(no air), has the proper coolant, air flow thru a clean(ish) rad, and an operating t-stat, the engine temp will pretty much stay the same once it gets to operating temp. The t-stat cannot open any more than full once the engine temp gets to the rated opening temp of the t-stat. In the time that it takes the t-stat to open, engine temps have already passed the rated opening of the stat, and therefore the stat will remain open.
A 165 deg stat will open at a lower temp than a 185 deg stat. If the engine remains running, the running temp will keep rising...the t-stat will not make it run any cooler....it's fully opened. The only thing that keeps temps in check at that point is air flow thru, and coolant flow in, the radiator. Idling in traffic will cause engine temp to rise, but the fan keeps air flowing enough to keep from overheating. Once moving again, air flow thru the rad will cool it back down. I can't see any scenario where the engine temp, once running, will cool itself back down enough to close the t-stat, even in extremely cold ambient temps.

In this particular case, I would be suspicious of  faulty temp sending unit, or gauge(or both), since measured temp at the upper radiator NECK was 180deg. The rad metal can't be at 180 if the coolant is only 165...right? 🙂



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Re: Another cooling question (12/14)
 1/25/23 11:10pm
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


Joined: 7/9/2003
Posts: 794

If you have a 165° thermostat and it opens at 165⁰ then what happens to keep the engine temperature from reaching 150° on a 30° day? Are you saying that the thermostat is either fully open or fully closed around the stated temperature?

Also in my example of a thermostat that was barely cracked open and the car would never reach operating temperature.

The way I understood it was that the wax in the pellet of the thermostat would expand and contract thereby controlling the temperature by modulating the flow through the radiator but it wouldn't be one or the other as the temperature changed.



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1973 L-82 4 spd

Re: Another cooling question (13/14)
 1/27/23 7:11pm
manchestersharkLifetime Member
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Hi, As long as we are on "Cooling" subject, Are the foam rubber radiator gaskets on the support really needed? For a mild drive and mild mannered engine, do they really aid in cooling enough to merit them being installed? 



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Re: Another cooling question (14/14)
 1/28/23 1:21am
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


Joined: 7/9/2003
Posts: 794

On a hot day, on the highway with the A/C on, they definitely help, especially with a big block.  YMMV

 



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1973 L-82 4 spd

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