You can’t trust thermostat ratings

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hotrod swinger

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I bought a 185 thermostat, it was stamped 185, yet my engine consistently runs at 170, no matter the season. Verified with a laser thermometer.

Is it worth the time and energy to swap it out?
 
Where are you measuring?

Thermal temp guns don't work accuritely on reflective surfaces.
 
I bought a 185 thermostat, it was stamped 185, yet my engine consistently runs at 170, no matter the season. Verified with a laser thermometer.

Is it worth the time and energy to swap it out?
The thermostat hasn't a thing to do with how hot your engine runs. Nothing. The temperature stamped on the thermostat is simply when it begins to open.
 
I don't think I'd worry about 170*. But if it's going to be one of things that you think about every time you drive, make time to swap it out. I learned to bite the bullet on those nagging little things that take up my valuable gray matter, lol.

I wonder if the laser thermometer could be off also? Could be a combination of the thermostat opening a little early and the thermometer reading low.
 
I don't think I'd worry about 170*
Everybody seems to be worried about overheating. If it's running 170° I would drive nd enjoy.

I wonder if the laser thermometer could be off also? Could be a combination of the thermostat opening a little early and the thermometer reading low.
The lazer's are quite accurate. They measure surface temperature and not coolant temp.
 
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The lazer's ar quite accurate. They measure surface temperature and not coolant temp.
Correct. This is why any nurse will tell you to add "about" 3-5 degrees to an infra red gun if you use it to take a person's temperature. The temperature of your forehead's surface isn't quite representative of your overall body temp.
 
The thermostat hasn't a thing to do with how hot your engine runs. Nothing. The temperature stamped on the thermostat is simply when it begins to open.

I get that it has nothing to do with maximum temperature, but I had understood the thermostat dictates the minimum temperature, which is what I’m concerned about.
 
The thermostat rating is the temperature of which it is fully opened. The thermostat starts opening a lot sooner but it's not fully open until the rated temperature. Fact.
You can take a 180 thermostat n put it in a pot of water on a lit stove..and with a thermometer in it you'll see it starts opening about 150 degrees.
We learned that in HS auto shop class.
 
I bought a 185 thermostat, it was stamped 185, yet my engine consistently runs at 170, no matter the season. Verified with a laser thermometer.

Is it worth the time and energy to swap it out?
You can use less fan, or a higher rating stat...but... idk. It's your car. Idt it would hurt it. There is an expansion rate at a given temp for cast iron and I guess you would want to maintain a range in regards to the clearances vs temp spikes @wot ...its really overthinking it though. Lol
 
I bought a 185 thermostat, it was stamped 185, yet my engine consistently runs at 170, no matter the season. Verified with a laser thermometer.

Is it worth the time and energy to swap it out?
Ratings on anything anymore it seems have a wider tolerance band than it used too
 
Of course I ended up changing the thermostat. What else would I do on a rainy day?

I bought a 195, the one that was installed was a 180.

Tested both last night, both close properly, the 180 opens at 160 and the 195 opens at 185. I installed the 195.
 
The thermostat rating is the temperature of which it is fully opened. The thermostat starts opening a lot sooner but it's not fully open until the rated temperature. Fact.
You can take a 180 thermostat n put it in a pot of water on a lit stove..and with a thermometer in it you'll see it starts opening about 150 degrees.
We learned that in HS auto shop class.
Gotta disagree with that. Everything I have ever seen or read stated that the temp on a thermostat was when it started opening. @RustyRatRod was an Oriellys manager for years, and I agree with him.
 
These were the temps they started to open.
Thank you for actually doing the footwork most people either just believe or deny it and never tested themselves.

They start opening before the temp rating at which they are fully open at.

People think they just POP open..lol.. yeah.. a big pressure spike is what you want...not.
 
Also my engine now runs at 180-200 instead of 160-180, so the thermostat definitely has an effect on operating temperature.
 
The thermostat rating is the temperature of which it is fully opened. The thermostat starts opening a lot sooner but it's not fully open until the rated temperature. Fact.
You can take a 180 thermostat n put it in a pot of water on a lit stove..and with a thermometer in it you'll see it starts opening about 150 degrees.
We learned that in HS auto shop class.
2 types of thermostats. Graduated and reverse poppet. Graduated are fully opened at 180, and poppet style start to open at 180. Quick open quick close. Poppet style typically cycle open and closed.
 
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