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Whats up ETCG’ers – I am pretty new here so bare with me :whistle:
Firt off a little back ground:
I have a 1985 Jeep CJ7 with a 4.2L inline six (258). Long story short – I was overseas for a very long time and it sat up for many years. I somewhat recently returned permanently to the US and have since set out on the process of getting it back to daily driver status. My jeep, while being a daily driver is also setup for mild to moderate offload capability. Its lifted 4″, 4.56 gears, has 35″ tires and a stock T5 Trans / Dana 300 trans/transfer case set up.
On to my situation – My jeep has always ran on the high side of the temp gauge and in traffic in La. heat it would be further up the scale than I cared for. In attempt to improve my jeeps ability to run cooler I installed a electric fan set up from a 99 Mercury Cougar. This is a popular mod among jeep enthusiast as the fan is pretty much a direct fit on the radiator with very little modification.
Once I got the fan installed I had to devise a way to control it. There are lots of after market variable speed controllers out there but with my current economic status I could not afford one. I wanted the fan to run as it was designed to run in its stock configuration – both fans running in both high and low speed. In order to achieve this I decided to run a 2 stage BMW temp switch (176/190*F dual temp switch Part # 61318361787) , mounted in the thermostat housing. I went to the local U-pullit and scavenged a 2 relay base and utilized an exterior electrical box and crafted my own fan control. Pretty simple and effective.
Here is my concern – it works. My jeep is running much cooler now. The needle on the gauge maintains around the center of the scale and further down on cool mornings or days in lite or no traffic. On hotter days in heavier traffic it will run up about 3/4 up the scale and pull down to half and control in that range. I have NO performance issues so far but I’ve been told that running the motor too cool can hurt my motor. Should I be concerned? I have been told not to trust the accuracy of the stock electrical gauge and the mechanical gauges are the way to go. What would be the best way to know for sure that my new found cooling success is not going to hurt my motor? What are the effects of under heating/over cooling?
If you made it through all of this thanks and any advice is greatly appreciated.
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This is about where my CJ ran during normal driving conditions – lite to moderate traffic. (before I did the electric fan mod)
Now it will reach almost to that point in heavy traffic but the high speed of the fan will pull it back down to about the mid point of the scale. On cool days though it runs close to the bottom of the scale and up to the middle. No performance issues at all…I just need to insure I get the most miles out of this engine that I can. To my pea brain cooler = better for the motor…but I’m not a pro.
It never hurts to monitor your Temp with a mechanical gauge, if you take it off road and do a lot of low speed high rev crawling it would at least give you piece of mind.
In my honest opinion cooler is better so i wouldn’t worry about it overly much, unless your running some sort of sensor based EFI and the computer never goes into closed loop because your running it under 160 F. Enjoy your Jeep.Pat
If it is in the middle your fine. If it never reaches operating temperature you will start getting moisture in your oil. Which means you would have to change your oil more often. But what you described is good. I would be more worried about it going 3/4 of the way up.
Temperature is a lot more critical on fuel injected engines. I’m guessing that your’s isn’t. That said, if you’re in the middle of the range I would say you nailed it and it’s not running tool cool. As for some of the dangers, I think on the top of the list is the cylinders getting washed out from incomplete combustion. Combustion needs a certain amount of heat to burn all the fuel. If you don’t burn it all it collects on the cylinder walls and can wash the oil away. Based on your description, I don’t think you have to worry about that. In fact, it sounds like you’ve done some pretty intelligent mods so far.
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