mr72

This post is exactly right!

It's all about air pressure. Venting the hood or removing the front engine bay cover below the bumper etc. all will decrease air pressure differential at the radiator, which will [in theory] reduce cooling efficiency. Whether it reduces it to the point that it would make a difference in real-world performance is another question. But I would have to think, anyone who thinks they need hood vents is probably experiencing marginal cooling system performance in the first place, so the last thing they'd want to do is reduce the cooling system efficiency.

ibeatmyjk

So by adding an aftermarket front bumper, fenders, hood, ect this would cause the air pressure to drop in the engine bay and would also cause the temp to marginally increase?

jeepmojo

as far as the engine cover removed did not effect the engine temp at all . Thats the way i remember the thread conclusion . Its there for a reason . Not just its great looks if were talking the same cover ?

mr72

Not necessarily. It would cause the cooling system to be less efficient. By how much, who knows? And whether that makes a difference for your Jeep in the conditions where you drive it, who knows?

When the engine is adding heat to the coolant faster than the radiator and fans can take it out, eventually the coolant pressure will be too high and the radiator cap will open, allowing coolant to escape. When this happens basically your engine is in the beginning of thermal runaway and it will overheat very quickly, there's nothing in the world you can do to prevent it. You have no choice when this happens but to shut off the engine, wait for it to cool (hours), refill the radiator, and then stop doing whatever you did that caused it to overheat or fix the broken stuff. Hopefully no head gaskets were lost in the incident.

Reducing cooling capacity or efficiency won't make it run hotter, it will just make overheating more probable.

mr72

The cover I am talking about is #4 in this piture:

Grand Umpah

Keep in mind, water has 25 times the heat transfer capacity that air has (Cooling 101: The Basics of Heat Transfer ), so keeping the water circulating in you engine (especially since it's actively driven by the water pump) is always going to be a better way to cool your engine compared to air.

While modifications to install hood louvres are fine if that's the look you're going for, it just isn't justified if you goal is to lower engine heat (in most situations).

Obviously, the above doesn't apply if there are problems with your water circulation and radiator cooling systems

jeepmojo

on the reply of what cover you meant . I thought you meant ornamental cover sitting up top of engine , Some people remove it thinking it adds heat .
Im still not sure myself if it truly does not add heat to the engine compartment the cover that says 3.6
mines still on ive never had a over heat , but it does get pretty toasty
my orig thermostat failed they replaced it and 11 months later it failed again , no over heat it was winter and about 9 degrees out . threw a code to replace housing and tt . (wierd) they revised the thermostat recently different part number still made in china though . i guess they been having issues the dealer said . These engines would be good to cook while out on the trail or just warm up a meal . tv dinners yould think

Tuto

Well to play safe I'm looking into installing an Engine Oil Cooler. .
Already have the transmission cooler in it.
I'm running a 181F thermostat and lower the temp on the fan using the flashP programmer.
The jeep runs in the range of 185-195 F Only during the summer (100F) AC turn On. In the express way at 75- 80 mph it hits 205-210F
I belief because the Warner Power Plant blocks a large area of the radiator and the AC on also makes it run hotter.
We will find out if w/ the Engine cooler the running temp will Change this summer.

mr72

It already has one, right? The 3.6 anyway.

Why? I suppose you have a[n outdated and incorrect] perception of what temperature is the right temperature for the engine to run? Modern engines, including the JK's 3.6, are designed to run hotter and have the appropriate equipment to keep it in the correct temp from the factory. If you are having problems with overheating additional cooling capacity or efficiency is what you need, not lower starting temperature. If the thing is going to overheat, it's going to overheat no matter the thermostat or cooling fan temp. In other words, as I think was already said in this thread, lowering the thermostat or fan temperature will do absolutely nothing to prevent overheating.

Move that winch out of the way, restore the original factory bumper, etc. Those things will restore the factory's cooling efficiency. If you cannot or will not do that, then you have to deal with airflow through the radiator and air pressure on each side of the radiator some other way. If you cannot or will not fix the efficiency problem then you have little choice but to add capacity ... I mean, in my Miata I had an aluminum 5-core radiator with nearly 4x the capacity of the stock radiator, because that's what it took for that car to handle rush hour traffic in Central Texas summers while running the A/C. Maybe my Jeep will have the same problem. But the point is you can't just reduce the thermostat temp and magically give the system more ability to remove heat from the engine. You just force it to operate in a less efficient part of its range more of the time. It will still overheat the same way.

Changing the thermostat and fan thermostat temperature is just the wrong approach. It's adjusting the wrong thing.

Tuto

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I have the 3.8 Engine.
The Newer 3.6 come w/ a Factory Transmission cooler.

I already install a Transmission cooler. Now I'm looking into installing an Engine Oil Cooler.
I did not just change the Thermostat to a 181*F . I also RE-program at what temp the Electric fan comes On. It has 3 speeds Low, Med and High.