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
I
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?
1973 L-82 4 spd
Right at 160
If your temp gun proves to be accurate, then I'd try another t-stat.
1973 L-82 4 spd
Maybe a 195
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?
Joel Adams
C3VR Lifetime Member #56
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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.
1973 L-82 4 spd
The outside temp was about 50 in New York however was running cool in warmer temps as well
Driving also 160-165
Ok possibly a defective stat I’ll try a new one and keep you updated thank you 73 shark
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? 🙂
Joel Adams
C3VR Lifetime Member #56
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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.
1973 L-82 4 spd
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?
On a hot day, on the highway with the A/C on, they definitely help, especially with a big block. YMMV
1973 L-82 4 spd