Most engines use a 195 degree thermostat. That gets the engine coolant up to that temperature at which point all internal parts have expanded and changed shape slightly to fit perfectly. To say that a different way, at other temperatures, especially when the engine is still cold, is when almost all engine wear takes place. That's why engines that routinely see long distance trips while warmed up reach really high mileages, like 440,000 on my '88 Grand Caravan, and why engines used almost only for real short trips don't get to a very high mileage before a lot of repairs are needed.
One thing you should be aware of is dash gauges are notoriously inaccurate, so don't get too concerned with exact readings. Their best purpose is for you to notice when something is out of the ordinary. In fact, most gauges don't even have numbers on them. Instead, they have "good" or "acceptable" ranges and "unacceptable" ranges.
Older vehicles had two coolant temperature sensors on the engine. One was a two-wire sensor for the Engine Computer. The other had a single wire. It was for the dash gauge. Both have extremely low failure rates because there's just one component inside them. Later models use just one sensor for the Engine Computer. Those are always very accurate. Coolant temperature as well as a lot of other engine data is shared with all the other computers, including the instrument cluster, so now the temperature information it receives is very accurate, but you still have the gauge itself that will vary between multiple vehicles.
If you really want to know the exact coolant temperature, use a scanner or now some of the more costly inexpensive fault code readers to see the temperature the Engine Computer is seeing. I found one of these data readers for my cousin for $35.00. They work fine, but the displays update painfully slowly for professional use.
To add another side to this story, on older Chrysler vehicles with electric radiator fans, those didn't get turned on until coolant temperature reached 210 degrees, then they turned off at 198 degrees. It is real common on a lot of GM vehicles for the fan to not get turned on until coolant is as high as 226 degrees. That is considered normal. Of bigger concern has to do with removing the radiator cap. Water, which makes up half of the coolant, boils at 212 degrees. That's why Chrysler picked 210 degrees to turn the fan on. Cooling systems, including a special valve in the radiator cap, allow the system to build up to 15 pounds of pressure. That pressure is not what is dangerous when you remove the cap. Doing so would give a little spurt of leaked coolant, then the excitement would be all over. The reason for that pressure is for every additional pound of pressure, the boiling point of the water increases by three degrees. 212 degrees plus 45 degrees means the coolant won't boil up to 257 degrees. If a hose springs a leak, that pressure is lost, the boiling point goes back to 212 degrees, and the water boils, expands, and escapes as really hot steam. The same thing happens when there's no leak, but the radiator cap is removed when the engine is overheating. The instant the additional pressure is lost, the water boils and is forced out of the radiator as steam or very hot liquid right next to your hand or face. This is why we're always told to let the engine cool before removing the radiator cap. Thanks to the extensive use of aluminum on today's engines, that can take as little as five or ten minutes.
Here's links to some dandy related articles that will offer more information:
https://www.2carpros.com/articles/engine-coolant-59420607
https://www.2carpros.com/articles/how-a-coolant-temperature-sensor-works
https://www.2carpros.com/articles/engine-cooling-system
https://www.2carpros.com/articles/radiator-pressure-test
https://www.2carpros.com/articles
Besides the water, coolant is also made up of alcohol. That won't change over time. However, all manufacturers provide recommended time intervals to replace the coolant. That used to be every two years. Today, three to ten years is common. There's two reasons for doing this. The first is acids build up in the liquid over time. That's from combustion gases working their way into the cooling system. That can't be avoided. We want to get those acids out. You'll find iron, aluminum, copper, brass, and tin in cooling systems. Any time you have two different metals and an acid, you get "galvanic action" which is a fancy name for corrosion. It is also the process by which batteries work. This corrosion leads to leaking radiators, heater cores, and if bad enough, leaking cylinder head gaskets.
The second reason for replacing coolant is the antifreeze part contains a number of additives, including corrosion inhibitors to prevent that corrosion I just mentioned, water pump lubricant, anti-foaming agents, and seal conditioners. It's those additives that wear out over time. They get replenished with the new antifreeze.
Be aware too, for a new problem to worry about, a lot of engines are developing leaking water pumps from the use of municipal tap water. This has something to do with the minerals in it that attack the water pump seal. We're supposed to use distilled water. When that is inconvenient, new coolant in a 50 / 50 mix is available. That is premixed with distilled water. That is its only advantage. Beyond that, you're paying for a half gallon of water. I prefer to buy straight antifreeze, then mix my own. The advantage is the ratio can be adjusted to reach the desired freeze point.
That is another point of confusion. Without continuing the long explanation, when testing the freeze point, colder is not better. The best combination of freeze point, heat dispersal, and system performance is reached when the freeze point is close to minus 35 degrees. Lower is not better and higher is not better.
Let me know if you have other questions.
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Friday, March 3rd, 2023 AT 4:01 PM
