Dude: which part? Will the HOAT leave the typical crusty residue?

 

It did on mine when my water pump started leaking.

 

if you checked it hot and the overflow bottle was low, then when it cools it'll suck the rest into the system.

What year JK? You need to use the G-05 HOAT coolant unless you have a 2013. Use the right stuff, don't use the "universal" coolant.

https://www.jk-forum.com/forums/jk-w...cement-124942/

 

Thank you and its an 08 with 51,000 miles so if there is white crusty stuff around it, it is leaking? And if there isn't then its not leaking correct? Or is there a way to test it

 

It's a over flow bottle. It's suppose to keep what ever water/air bubbles from the raid from dropping all over the ground. Your cap does not in any way shape or form suck water back in to the raid. It's not made to do that. Leave the jeep cold and pop the cap off and crank it up. Let it warm up and see what happens. Then top it off and cap it again. Run it and don't mess with it anymore. If its not over heating then there is no problem. I have never seen mine over heat and that offroading in 120+ climbing rocks in Vegas for 5+ hours. Still ran at normal temps.

 

Not to hijack, but this cooling system also has no motor (clutch) fan (presumably to lower fuel consumption ever so incrementally to serve the Manufacturer's Fleet Rating - not sure what that is precisely called).

Wouldn't the 3.8 be better served with a proper motor fan as well as the electric (radiator) fan?

 

Good question. But I have never had mine ogre heat and I live in Vegas. Even offroading and stop and go driving its still normal. I asked a friend who has had one longer than me and he said his did it once. But he was drifting in a field at high rpm. Stopped and let the motor run for a few and it cooled down fast. If your worried about it get the hood louver cut out and keep the motor bay cool.

 

It is important to note that these gauges are "steady state" gauges. This has been pretty common on passenger vehicles and motorcycles (water cooled) for the last ten+ years. Notice how quickly your gauge comes to "normal" and stays there. It will not show the temp change when the thermostat opens (perhaps a 30˚change). It will not show the temp difference between 215˚ and 235˚ when the radiator fan is programmed to change speed (low to high). It's all "normal operating temperature." Pretty likely (no hard data here), the needle will point straight up from about 135˚ to 235˚. Maybe someone here can tell us the point at which the gauge will actually read *hot* - over 250˚ ? IDK

Eliminating the (motor) fan isn't about making the motor last longer, the coolant system function better, or reduce the (infamous) oil consumption.

Be well aware what the gauge is really telling us: "normal operating temperature."

 

Modern caps are designed with two-way valve system.

for example:
Hidden genius behind an engine cooling system -- the radiator cap - YouTube

 

Had to say. Post some photos and someone will chime in.