[bmboll]

I recently got a Jeep and it is beginning to see it's first AZ summer with me. Usually the temp gauge stays right around 210. It has been in the upper 90's and the temp is rising. With the a/c on in city traffic the gauge went up to in-between 210 and 235 marking. I would guess the temp was around 225. The upper 90's is mild for summer temps. We will see 110+ from time to time. I am concerned about how hot my Jeep is running and what it will be running at when it is 110. I know a new thermostat would be a possible fix but I have read people advising against it. Does anyone else have similar problems?

[billy boy]

Mine stays at 210 always. I live in Phoenix, Bill

[Jerry Bransford]

Stay with the factory 195 degree thermostat as simply installing a lower temperature thermostat cannot force the engine to lower its normal operating temperature. If your engine starts to overheat, look for problems like the radiator starting to clog from hard water deposits, a stuck thermostat, or perhaps the fan clutch going bad.

[mdm]

Look for mud or other foreign material blocking the airflow through the radiator.

[bmboll]

The coolant was flushed with the 30k mi service at the dealer prior to me purchasing it. That was 6k mi ago. The radiator is very clean. How about the coolant mixture. I have one of those coolant mixture testers. It said to do test it when it was cold but I tried it when it was warm. It seems like it is "ritch" in anti-freeze. I will have to check it when it cold to be sure I am getting a good reading. Could this be the problem?

[de6w6it]

If you have a lower temp thermostat, it will open sooner, allowing circulation through the radiator at a lower temperature. This will cause the engine to run at a lower temperature, because it is being cooled more when then thermostat is open than when it is closed. The motor is going to generate the same amount of heat no matter what you do, it's just how much it is able to dissipate that is key. When the temperature is higher outside, it is harder for the motor to give off heat to the atmosphere. So by flushing out crap in the radiator, making sure the fins are clean, making sure the thermostat is not stuck closed, you are enabling the system to dissipate more heat, which is what having a thermostat that opens at a lower temperature does, it enables the system to dissipate more heat, because it is open more. So aside from say extra friction in the motor from there being no oil or something, the motor itself is always going to generate the same amount of heat. Anything you do externaly is going to change the dissipation proerties. You temp gauge is gauging the temperature of the coolant flowing through the water pump. If the water/coolant is allowed to flow through the radiator, the temperature will be lower because it is giving off heat through the radiator.

[Border Dave]

Originally Posted by bmboll

The coolant was flushed with the 30k mi service at the dealer prior to me purchasing it. That was 6k mi ago. The radiator is very clean. How about the coolant mixture. I have one of those coolant mixture testers. It said to do test it when it was cold but I tried it when it was warm. It seems like it is "ritch" in anti-freeze. I will have to check it when it cold to be sure I am getting a good reading. Could this be the problem?

If your coolant mixture is more than 50%, yes, it can cause overheating problems in extreme environments since coolant doesn't transfer heat as well as water. I run about 20% coolant/80% water and my jeep now runs about 210 or so all the time. You could also try Redline Water Wetter to this mixture. Watter Wetter promotes heat absorption and transfer.

As far as the thermostat goes, like Jerry said, there is no point in changing it to a lower temp. if the cooling system doesn't have the ability to keep it at that temp. A more efficient aluminum radiator and a more efficient fan are good upgrades if your jeep is running too hot and you've determined that you don't have any of the underlying problems that Jerry mentioned.

[Jerry Bransford]

Originally Posted by de6w6it

If you have a lower temp thermostat, it will open sooner, allowing circulation through the radiator at a lower temperature. This will cause the engine to run at a lower temperature, because it is being cooled more when then thermostat is open than when it is closed. The motor is going to generate the same amount of heat no matter what you do, it's just how much it is able to dissipate that is key. When the temperature is higher outside, it is harder for the motor to give off heat to the atmosphere. So by flushing out crap in the radiator, making sure the fins are clean, making sure the thermostat is not stuck closed, you are enabling the system to dissipate more heat, which is what having a thermostat that opens at a lower temperature does, it enables the system to dissipate more heat, because it is open more. So aside from say extra friction in the motor from there being no oil or something, the motor itself is always going to generate the same amount of heat. Anything you do externaly is going to change the dissipation proerties. You temp gauge is gauging the temperature of the coolant flowing through the water pump. If the water/coolant is allowed to flow through the radiator, the temperature will be lower because it is giving off heat through the radiator.

Don't forget that a 195 degree thermostat is already fully open when the engine is running at its normal design 210-220 degree temperature. The 195 degree thermostat is already fully open and allowing maximum flow but the engine is still running at 210-220 degrees. So what does that do to your argument?

[de6w6it]

I was going on the thought that it did not stay fully open all the time. From what I could see with mine, the temp goes up to that, then would drop, then slowyl creap up, then drop, so based on that experience I figured that the thermostat was not always open. If it is fully open all that time, than I definitely agree, a lower temp thermostat will do nothing but take longer to warm up in the cold.

[Border Dave]

In Arizona in the summertime, let me assure you, once the thermostat opens, it stays open.

[de6w6it]

Well, then I would agree, a lower temp thermostat is not going to help.

[de6w6it]

Maybe a high flow water pump could help?

[Border Dave]

Originally Posted by de6w6it

Maybe a high flow water pump could help?

That all depends on the motor and cooling system. If a water pump flows coolant too fast, the coolant won't have enough time in the block to absorb the heat, nor enough time in the radiator to cool down. I can't say if a high flow water pump would benefit a TJ or not, as I'm still using the factory unit.

[Jerry Bransford]

Originally Posted by de6w6it

Maybe a high flow water pump could help?

Engines are cooled more efficiently when the coolant does not flow too quickly. And if an engine is overheating, fix the problem. Just having as a goal a cooler running engine isn't always the good thing some always seem to think it is. The engineers have designed it to run at 210 or so degrees as it runs cleaner, pollutes less, and can more easily pass the smog tests. I've had more than one smog test fail when my engine wasn't yet fully warmed up. In fact before I learned how thermostats worked, I had a cooler thermostat installed and it wouldn't pass the smog test the next time it was required. The quick-thinking smog technician asked if it was running a cooler thermostat and when I confirmed it, he installed the correct thermostat and it then immediately passed the smog test.

[bmboll]

Originally Posted by Border Dave

If your coolant mixture is more than 50%, yes, it can cause overheating problems in extreme environments since coolant doesn't transfer heat as well as water. I run about 20% coolant/80% water and my jeep now runs about 210 or so all the time. You could also try Redline Water Wetter to this mixture. Watter Wetter promotes heat absorption and transfer.

As far as the thermostat goes, like Jerry said, there is no point in changing it to a lower temp. if the cooling system doesn't have the ability to keep it at that temp. A more efficient aluminum radiator and a more efficient fan are good upgrades if your jeep is running too hot and you've determined that you don't have any of the underlying problems that Jerry mentioned.

Maybe I will try letting out a gal. of what I have and add a gal of dist. water