403 olds running temp

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Old Mar 4, 2026 | 08:28 AM
  #41  
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Originally Posted by CANADIANOLDS
Directly from a thermostat manufacturer. it keeps the engine within a specific temp range .
it prevents overheating, that’s what’s called the upper range.
https://www.facebook.com/share/r/1Ac...ibextid=wwXlfr
Yes it does keep the minimum engine temp in a range,(read the last paragraph of your link) It cannot control the 2 question posed below.

How will it prevent engine temps that keep creeping up after the thermostat is fully open?

If a 180* thermostat maintains engine temp @195-200* fully open, how does a 160* lower that temp when it is fully open?

Last edited by oldcutlass; Mar 4, 2026 at 02:10 PM.
Old Mar 4, 2026 | 08:46 AM
  #42  
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Originally Posted by oldcutlass
Yes it does keep the minimum engine temp in a range, It cannot control the 2 question posed below.
How will it prevent engine temps that keep creeping up after the thermostat is fully open?

If a 180* thermostat maintains engine temp @195-200* fully open, how does a 160* lower that temp when it is fully open?
thanks for agreeing with me on the stat keeping the eng temp WITHIN a RANGE. but your RANGE of the 180 you stated , isn’t 195 to 200. In a properly operating cooling system it’ll keep the temp between 180 and 195 max

the 160 stat keeps the max temp lower , by passing water to the rad sooner than the 180 stat did because it’s open at a lower temp.

all of you keep forgetting the cars cooling system is over designed for a reason…that over design is what’s being used to keep an engine cooler when a lower temp stat is installed.

therefore a lower temp stat design allows for a lower max operating temp than a higher temp stat design.

again here’s the falsehoods that have been said here.
a hotter design thermostat allows for a quicker warm up…that’s not true .the engine will warm up at the same rate no matter what stat is in it.. a hotter stat allows for a higher temp before opening, then maintains a higher temp range

a stats job is not done once it opens. it prevents overheating by controlling the max operating temp, wether that’s a higher or lower max operating temp…the max temp is still controlled by the stat by controlling the water flow through the rad

Last edited by CANADIANOLDS; Mar 4, 2026 at 08:58 AM.
Old Mar 4, 2026 | 08:55 AM
  #43  
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Originally Posted by oldcutlass
Wall thermostats do not keep temps within a range, they are set to the minimum temperature that you want your space to be. Depending on what it is set to, for heat it turns the heater on if the temp drops below the set temp, and for cooling it turns the a/c on if the temp is above the set temp. It does not do both at the same time.

How does the thermostat in a car control the temperature if it slowly keeps creeping up once it's fully opened? How does your home thermostat cool the house back down when set to heat if the temperature keeps rising past it's set temp or when set to cool keeps dropping way below the set temp?
the thermostats function in a house controls the temp in the room…simple as that. that’s why it’s called a thermostat.

the thermostat in a car controls the temp of the engine, that’s why it’s called a thermostat.

if the temp of the engine continues to creep up, and the thermostat is known to be functioning properly, the cooling system itself is malfunctioning.. the engine temp should not continue to creep up.


Old Mar 4, 2026 | 09:00 AM
  #44  
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Everyone needs to read that Motorad explanation..then write it out 100 times on the blackboard.

maybe it will sink in.

Per Motorad…a stat is designed to keep an engine within a temp range and prevent overheating

Last edited by CANADIANOLDS; Mar 4, 2026 at 09:11 AM.
Old Mar 4, 2026 | 09:57 AM
  #45  
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Originally Posted by CANADIANOLDS
Everyone needs to read that Motorad explanation..then write it out 100 times on the blackboard.

maybe it will sink in.

Per Motorad…a stat is designed to keep an engine within a temp range and prevent overheating
I did read it, re-read the last paragraph it is designed to regulate the minimum operating temp. You didn't answer the 2 questions I asked above.
Old Mar 4, 2026 | 10:12 AM
  #46  
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Originally Posted by oldcutlass
I did read it, re-read the last paragraph it is designed to regulate the minimum operating temp. You didn't answer the 2 questions I asked above.
which two questions?

point out where Motorad says its only designed regulate the minimum temp? screen shot or circle where it says that

Last edited by CANADIANOLDS; Mar 4, 2026 at 11:05 AM.
Old Mar 4, 2026 | 12:32 PM
  #47  
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The thermostat does regulate minimum and maximum temperature, IF everything is functioning as intended. I find they open around the rated temp and go within 10 degrees above the rated temp on a properly functioning system. Of course air and coolant flow along with a properly sized system is needed for that to happen. I had nearly every conceivable issue with the 403 in my 88 Cutlass. I made sure all the factory dams were in place. The one underneath the rad was damaged, patched, them replaced, no difference. Some things made small differences, overdrive vs underdrive pullies, multiple different radiators, 7 blade vs 5 blade clutch fan about the same as the Plymouth Breeze dual fans. A closed water pump made no noticeable difference. The thermostats only made minor differences except the Mr.Gasket which closed at higher speeds. Around town, it worked great. The GN rad surround ultimately fixed it, dropped temps 30 degrees. The 88 is the only vehicle that ran 30 degrees above thermostat temp, 60 degrees towing but it was obviously air flow related. I also found the temperature gauge read 10 degrees high, made it look even worse than reality. I learned more than I wanted about cooling system and parts quality and why I don't miss that car.

Last edited by olds 307 and 403; Mar 4, 2026 at 12:35 PM.
Old Mar 4, 2026 | 01:19 PM
  #48  
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I haven't seen one post in here that explains HOW, specifically, the thermostat controls maximum temperature. Just several that say that it somehow does.
Old Mar 4, 2026 | 02:10 PM
  #49  
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Originally Posted by CANADIANOLDS
which two questions?

point out where Motorad says its only designed regulate the minimum temp? screen shot or circle where it says that
They are in bold print in post 11 And read the last paragraph in the Motorad description you posted.
Old Mar 4, 2026 | 02:40 PM
  #50  
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Originally Posted by BangScreech4-4-2
I haven't seen one post in here that explains HOW, specifically, the thermostat controls maximum temperature. Just several that say that it somehow does.
It doesn't. The cooling system is able to dissipate more heat than the engine can generate - in my car, I found that with a stuck-open thermostat the coolant runs at 130ºF. So with everything operating properly, the thermostat regulates flow through the radiator to keep the coolant at a temperature that allows some amount of flow - if the coolant temp goes down, the thermostat closes more to restrict flow and the temperature goes up, and that warmer coolant then causes the thermostat to open a bit more, which then allows more coolant flow through the radiator causing the coolant temperature to decrease. So the amount the thermostat is open is dithering around its operating temperature point and the coolant is maintained at that temperature.

This is basically what the Motorad information says.
Old Mar 4, 2026 | 02:58 PM
  #51  
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Originally Posted by Fun71
It doesn't. The cooling system is able to dissipate more heat than the engine can generate - in my car, I found that with a stuck-open thermostat the coolant runs at 130ºF. So with everything operating properly, the thermostat regulates flow through the radiator to keep the coolant at a temperature that allows some amount of flow - if the coolant temp goes down, the thermostat closes more to restrict flow and the temperature goes up, and that warmer coolant then causes the thermostat to open a bit more, which then allows more coolant flow through the radiator causing the coolant temperature to decrease. So the amount the thermostat is open is dithering around its operating temperature point and the coolant is maintained at that temperature.

This is basically what the Motorad information says.
there ya go…except most cooling systems have a small bypass so the system doesn’t get temp spikes in any particular area ..some coolant does flow even when dead cold

the Olds bypass is the little hose at the front of the stat housing that connects to the top of the water pump. bypasses are always close to the stat

you nailed everything else

Last edited by CANADIANOLDS; Mar 4, 2026 at 03:37 PM.
Old Mar 4, 2026 | 03:11 PM
  #52  
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Originally Posted by olds 307 and 403
The thermostat does regulate minimum and maximum temperature, IF everything is functioning as intended. I find they open around the rated temp and go within 10 degrees above the rated temp on a properly functioning system. Of course air and coolant flow along with a properly sized system is needed for that to happen. I had nearly every conceivable issue with the 403 in my 88 Cutlass. I made sure all the factory dams were in place. The one underneath the rad was damaged, patched, them replaced, no difference. Some things made small differences, overdrive vs underdrive pullies, multiple different radiators, 7 blade vs 5 blade clutch fan about the same as the Plymouth Breeze dual fans. A closed water pump made no noticeable difference. The thermostats only made minor differences except the Mr.Gasket which closed at higher speeds. Around town, it worked great. The GN rad surround ultimately fixed it, dropped temps 30 degrees. The 88 is the only vehicle that ran 30 degrees above thermostat temp, 60 degrees towing but it was obviously air flow related. I also found the temperature gauge read 10 degrees high, made it look even worse than reality. I learned more than I wanted about cooling system and parts quality and why I don't miss that car.
you get it… that’s two guys so far.
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