The myth: low temp thermostats, electric fan conversions & "performance" radiators
- Thread starter Chris
- Start date
There is a change in something on the later model 4.0's. Before, it is the basic fill it, run the engine, thermostat opens, coolant circulates, top it off, watch the coolant for level changes and keep it topped off, simple, works like it should.
On the later ones or maybe the later thermostats, all the same except right as the thermostat opens, it kicks a big air bubble that blows out a couple quarts of coolant, makes a mess, cold coolant being run through the engine closes the thermostat and it repeats with a real danger of an overheat condition because you can't keep coolant in it.
We have solved the problem by drilling a 1/8" hole beside the jiggler in the flange and putting that at the top. No issues with the coolant kick and they bleed the air out of the system easily.
OP
Any idea as to what the reason was for them changing the thermostat on the later models?
Wombat
TJ Enthusiast
After installing a Golen 4.6 with a Flow Kooler - High Flow Water Pump the temperature is reading well below 100c
The stock engine use to run at about 100 c and I never had an issue with overheating even when the ambient temperature was 40 c +
My oil pressure is reading a bit higher than the stock engine but it might need to replace the sender.
I'll ring Chad and ask him what he thinks this is happening but any other ideas as to why?
The stock engine use to run at about 100 c and I never had an issue with overheating even when the ambient temperature was 40 c +
My oil pressure is reading a bit higher than the stock engine but it might need to replace the sender.
I'll ring Chad and ask him what he thinks this is happening but any other ideas as to why?
I'm halfway done with the Thermostat.
The old one was MotoRad brand and probably a fail-safe model (it has these extra clips that the Stant does not have).
It was stuck in the open position (the Jeep has not been started for 2 days), when I pushed on the center it closed back up.
Most of the videos I watched must have drained the system because they didn't spill ANY coolant.
So I spilled radiator fluid all over the belt and the front of the engine is a good rinse with the hose sufficient or should I do something else? I'm glad I put a catch tray under the Jeep before I started...
The old one was MotoRad brand and probably a fail-safe model (it has these extra clips that the Stant does not have).
It was stuck in the open position (the Jeep has not been started for 2 days), when I pushed on the center it closed back up.
Most of the videos I watched must have drained the system because they didn't spill ANY coolant.
So I spilled radiator fluid all over the belt and the front of the engine is a good rinse with the hose sufficient or should I do something else? I'm glad I put a catch tray under the Jeep before I started...
Pour a bucket of hot water on it. That will rinse the coolant off faster than just the garden hose. Also the clips hold that old stat open which defeats the purpose of a thermostat.I'm halfway done with the Thermostat.
The old one was MotoRad brand and probably a fail-safe model (it has these extra clips that the Stant does not have).
It was stuck in the open position (the Jeep has not been started for 2 days), when I pushed on the center it closed back up.
Most of the videos I watched must have drained the system because they didn't spill ANY coolant.
So I spilled radiator fluid all over the belt and the front of the engine is a good rinse with the hose sufficient or should I do something else? I'm glad I put a catch tray under the Jeep before I started...
Last edited:
ejay
TJ Addict
I'm going to disagree here in part. I can tell a noticeable difference when I'm in stop and go L.A. traffic, or desert trails in 110 degree heat vs cooler temps or conditions in regard to my A/C. When I put my louvers in, it helped, some. I'm still on the fence as to if an electric fan would be a good investment. Do I think it would save me fuel as some kits claim? Not noticeably, of course. Less noisy, sure. Of course, there are other problems associated with electric fans. (Water crossings) But, they usually come with an in-cab kill switch. Plus, mechanical clutch fans also have their own water crossing issues. Not that I'm doing a lot of water crossing.
To put it simply, belt driven fans are parasitic to your engine. Electric fans are not. At least they aren't in the same way. Plus, if you cool your engine bay better, you're more likely to stay heat soak issues. So I don't think that it's a total waste of money. But, it's one more thing to break on the trail.
To put it simply, belt driven fans are parasitic to your engine. Electric fans are not. At least they aren't in the same way. Plus, if you cool your engine bay better, you're more likely to stay heat soak issues. So I don't think that it's a total waste of money. But, it's one more thing to break on the trail.
Both fans take energy from the engine to operate, they are both parasitic. Mechanical fans are much more powerful and much more efficient. Electric fans take power from the alternator, convert it to electrical with a large loss then the fan motor converts it back to mechanical with another large loss. It leaves you with a much larger draw on the engine overall and a much weaker fan.
ejay
TJ Addict
Not a horsepower draw. Like I said, it's parasitic in another way. I'd venture to say that mechanical fans, although probably less problematic, are more efficient and less of a strain on the engine. That's why nearly all newer vehicles have them in place of mechanical fans.
There is no free ride. Anything that induces drag on the engine is a horsepower draw. All newer vehicles have e-fans due to packaging and they couple that with a radiator with more efficiency due to the inefficiency of the fan.
To add to what Blaine says you can turn an electric fan off and you can't turn a mechanical fan off. That's another reason modern vehicles have them, they can run on the freeway for hours and hours with no power draw at all and that's a big deal as far as economy goes.
To be fair though, there is very little horsepower being used with a properly functioning fan clutch.
ejay
TJ Addict
While running the electric fan is less efficient. While not running the electric fan is more efficient so if the fan is off more of the time the electric wins. If the fan is always running the mechanical wins. Does that make sense?
I ran an electric fan in my ‘99. Hooking up the fan temp switch and mounting the fan was a big pain. I figured to get faster heat in the winter. When the brackets started to crack I changed back to the belt fan with a new clutch and I couldn’t tell the difference. Had heat the same distance from the house. I guess the engineers new what they were doing.
I think the elephant in the room is the fact that there aren't any electric fans made that flow enough air to equal the mechanical fan on a 4.0.
ejay
TJ Addict
The FF Dynamics electric fan kit I've been eyeballing for some time moves 3000 cfm. Considering it's on an electric thermostat (to your previous post) and claims it runs only as needed, I'd say it's a good bit of kit all things considered. Though they make some bold claims as to fuel savings. It clamps with a gap free aluminum housing to the radiator. That is air flow you're not going to get with a mechanical fan and its gaps in the shroud.
Wombat
TJ Enthusiast
I was let to believe they changed the thermostat on the 2000 and up to open at a higher temp to gain better performance, reason being the greater the difference between the ambient and operating temp the more efficient the combustion. Nevertheless I don't think it makes much difference.
Wombat
TJ Enthusiast
Agreed but on a hot day with the aircon running I could feel a noticeable loss of power taking off after stopped at traffic lights
I did the math on how much air the TJ fan flows once when I was having a discussion about grill inserts. You don't want to hear the numbers. Please report back if the electric fan works for you. I don't want to be negative so I won't, it would be cool if you found something that works.