G-Bodydude1983

Not-quite-so-new-guy
Aug 1, 2018
21
3
I have a 185 degree thermostat in my el camino at the moment, when the car is first cold it gets up to almost 200-210 degrees before the thermostat opens up and cools off the engine. Afterwards it acts completely normal. Is this typical behavior or should I replace it?
 

69hurstolds

Geezer
Supporting Member
Jan 2, 2006
6,395
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185 is when it first starts to open. It won't be fully open until the gage reads somewhere higher than that. Is the gage correct? Coolant still look clean and not cruddy/lumpy? Did it suddenly start happening or was this all along since changing the T-stat?

You may have a big air bubble in the system somewhere? It seems as if your overflow tank and rad cap are working properly and filled to the minimum levels, you should have worked the air out of the system, though.

I know on an LS engine, you got to work those air bubbles out of the system. PITA sometimes. Just went through that changing out the T-stat and coolant on the 2010 Camaro.

If it's cycling fine and not overheating otherwise, it may just be an anomaly of your cold start up. If it doesn't get over 210 before it starts cooling off then you're likely just looking at a slow reaction time of the gage.

Hard to determine if something's wrong without actually seeing it.
 
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airboatgreg

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Oct 2, 2016
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Sounds like it is working normal to me. That car should probably have a 192 in it. Remember, the thermostat does not dictate the operating temperature. The above post is right.
 
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69hurstolds

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Jan 2, 2006
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Just to add...If you have say, a quick sensing element for your gage, that could show you a higher delta T, or temperature difference between the radiator coolant and engine coolant when the T-stat starts to open as well. On a cold start up, even if the t-stat sees 185, the temperature will keep on rising slightly at the sensor as the hotter coolant moves through the engine passages (still picking up heat from the engine) to go on by the sensor. The colder coolant still has to enter the system and reach the gage sensor, which takes a few seconds. It's like when you go to Wal-Mart and know the bathrooms are in the back of the store instead of the front. You have to go by a lot of stuff until you start to get relief.

So the temperatures continue to rise until enough colder coolant mix reaches the sensor. This could cause your initial surge in temperature above 200 but as the t-stat opens further, a higher delta T exists, so you will see the most change in coolant temps after the T-stat opens. Once the t-stat is open, then the coolant temps stabilize as the system is now in full operating mode with the radiator in play. And if it's cold enough outside and your system is super-efficient, you may see the temperatures fluctuate some until the temperatures stabilize. Regardless, the engine will find its operating temperature on its own. If it's 205, ok, fine. If it's 250 or 260 or higher...start to worry. As airboatgreg pointed out, the T-stat has absolutely nothing to do with your coolant system's operating temperature. Design, materials, layout, and all of the entire cooling system is what determines your engine's operating temperature.

If you leave the thermostat out, it's not going to do anything bad, unless your system NEEDS a restriction at that point. Other than take forever to warm up. If the car companies could get away with it, they'd never put them in. But for most cars, it is a crucial point of helping in lowering emissions by getting the engine up to operating temperatures quickly and it also helps in getting the heater core warm on those 15 degree F days. Plus, kept the customers from whining about poor cold performance on initial startup. So 160 or 180, 185, 192, 195...pick your T-stat. On the street, that won't matter much. A 185 or 192 difference in T-stat setpoints likely won't even be noticed in your daily driver.
 

airboatgreg

Comic Book Super Hero
Oct 2, 2016
2,530
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Well put. Most engines need a restriction or the coolant circulates to fast. Not allowing for heat transfer from the engine to the coolant. In my opinion you want the engine to get to normal operating temperature as soon as safely possible. Get the condensation out of the crankcase, engine runs better, uses less fuel, gets the feet warm and fewer emissions.
 

Clone TIE Pilot

Comic Book Super Hero
Aug 14, 2011
3,054
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Galaxy far far away
M
Just to add...If you have say, a quick sensing element for your gage, that could show you a higher delta T, or temperature difference between the radiator coolant and engine coolant when the T-stat starts to open as well. On a cold start up, even if the t-stat sees 185, the temperature will keep on rising slightly at the sensor as the hotter coolant moves through the engine passages (still picking up heat from the engine) to go on by the sensor. The colder coolant still has to enter the system and reach the gage sensor, which takes a few seconds. It's like when you go to Wal-Mart and know the bathrooms are in the back of the store instead of the front. You have to go by a lot of stuff until you start to get relief.

So the temperatures continue to rise until enough colder coolant mix reaches the sensor. This could cause your initial surge in temperature above 200 but as the t-stat opens further, a higher delta T exists, so you will see the most change in coolant temps after the T-stat opens. Once the t-stat is open, then the coolant temps stabilize as the system is now in full operating mode with the radiator in play. And if it's cold enough outside and your system is super-efficient, you may see the temperatures fluctuate some until the temperatures stabilize. Regardless, the engine will find its operating temperature on its own. If it's 205, ok, fine. If it's 250 or 260 or higher...start to worry. As airboatgreg pointed out, the T-stat has absolutely nothing to do with your coolant system's operating temperature. Design, materials, layout, and all of the entire cooling system is what determines your engine's operating temperature.

If you leave the thermostat out, it's not going to do anything bad, unless your system NEEDS a restriction at that point. Other than take forever to warm up. If the car companies could get away with it, they'd never put them in. But for most cars, it is a crucial point of helping in lowering emissions by getting the engine up to operating temperatures quickly and it also helps in getting the heater core warm on those 15 degree F days. Plus, kept the customers from whining about poor cold performance on initial startup. So 160 or 180, 185, 192, 195...pick your T-stat. On the street, that won't matter much. A 185 or 192 difference in T-stat setpoints likely won't even be noticed in your daily driver.

Quick warm up also extends engine life and oil life. Engines wear much faster when cold and very slowly once fully warmed up. These days a 160 T stant is way too cold, better off staying with a stock 195 T stant.
 
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Clone TIE Pilot

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Aug 14, 2011
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Well put. Most engines need a restriction or the coolant circulates to fast. Not allowing for heat transfer from the engine to the coolant. In my opinion you want the engine to get to normal operating temperature as soon as safely possible. Get the condensation out of the crankcase, engine runs better, uses less fuel, gets the feet warm and fewer emissions.

That is false, you can't circulate coolant too fast. In fact heat transfers faster when there is a greater temp difference. The restriction causes more turbulance in the coolant flow inside the black to help reduce airpockets and low flow hot spots.
 

airboatgreg

Comic Book Super Hero
Oct 2, 2016
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That is false, you can't circulate coolant too fast. In fact heat transfers faster when there is a greater temp difference. The restriction causes more turbulance in the coolant flow inside the black to help reduce airpockets and low flow hot spots.
Disagree.
 

Clone TIE Pilot

Comic Book Super Hero
Aug 14, 2011
3,054
113
Galaxy far far away
Q = M x C x Delta T.

Q = heat transfer rate
M = mass flow rate
C = Constant ( the specific heat of water, which is a measure of how much heat energy a material such as water can store or absorb heat without changing its temperature).
Delta T = fluid temp out - fluid temp in or final temp - beginning temp.

Looking at the formula above, increase flow rate will increase heat transfer rate.

For those curious, the specific heat of water is 4182J/kg C. Iron is 449, steel is 490, air is 1,005.
 
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69hurstolds

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Jan 2, 2006
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I was going to toss out that formula yesterday, but figured it was a bit of a discussion for a different time. Increasing mass flow rate is a huge key in helping reduce overheating issues in traffic. On some cars in the late 60s, GM used to have ported vacuum for their distributors, they used a feature with a TVS to switch to manifold vacuum when temperatures rose too high. This advanced the distributor which increased rpm, which in turn rotated the water pump and fan faster. This increased mass flow rate of the air and the coolant through the system, and the hope was to reduced temps. Once the temps were reduced, the TVS switched back to ported vacuum for the distributor. And now, there's computer controls to turn on fan(s) as needed and such.

The potential problem with too much mass flow rate is that at some point, you'll have higher risks for EROSION. The water in the system has to turn at some point (a design thing) and will eat away areas of the metal over time (a materials thing). Although I don't think you could reach those sort of flows in a G-body's coolant system practically, regardless of what you do, especially with the small impeller water pumps that cars normally come with.

When in the Navy and at commercial power plant, periodic steam generator tube inspections were done in part to check erosion effect issues, and either tubes were plugged or sections replaced as needed.

The major takeaway here should be that many people TEND to forget about their coolant systems until something goes wrong that gets their attention. Which by then it's too late. You need to change your coolant periodically, and make sure you take care of any leaks. This goes for daily drivers as well. I know most of us with our G-bodies may not drive them every day. That's why it's important to stay on top of things even more with a car that's only driven periodically. Brown sludge in your coolant overflow tank? If so, it's in your engine and radiator too, clogging cooling passages and hurting cooling performance. Don't let that go. If you need to flush the system, then flush it. With proper maintenance ALL over the car, you should maximize the life of your coolant system and your car. Cracks, crunchy, hard, or mushy hoses when you grab and squeeze them? Cracked drive belt surfaces? Replace them! Use your best judgement on that. It's your car. Don't have it strand your azz on the side of the road when you need it most.
 
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