Jk overheating

[Mark A Fernandez]

So I replaced the radiator and thermostat on my 07 jk. Burp the system & still overheating. The top radiator hose & the 2 coming from the heater core are all hot. Only the lower hose is cool to the touch after jeep has been running. I was thinking maybe my water pump but not sure how to tell. Any help would be greatly appreciated.

 

[JPNinPA]

What made you change the radiator?


When burping the system you should see the fluid moving.
Was it overheating before changing the radiator and thermo?
What temp thermo?
What lb radiator cap?
What temp does it read on the gage just before overheating?

How long before it overheats?
When idling?
After you shut it off?
Only when not driving?
Does it happen at speeds above 35 mph"
Do you have anything in front of or narrowing the grill openings?

Any water in the oil (milkshake)?
Any moisture in the exhaust?

 

[Mark A Fernandez]

Wasn't overheating before, radiator had a crack. Decided to change the thermostat since I was tearing it apart. I can't make it down the street without it overheating. Doesn't happen on idle.

 

[JPNinPA]

If you could idle long periods but overheat while driving.

Stock replacement?



What brand and part number thermo?

Did you reinstall the spring? Check that the lower hose does not collapse when revving the engine.


Did you install any high flow thermo, housings or water pump?
No offense but did you install the thermo in the correct direction?
Is there anything in front of your radiator?
Is your belt tight or slips at high rpm?
Your radiator cap should be 18 lbs.
Is your overflow connected and not leaking?
From cold start your jeep do you see a stream of bubbles? Tiny bubbles?

 

[Mark A Fernandez]

Haven't changed out the water pump yet.

Didn't pay attention to the bottom hose collapsing.

No offense taken, the thermostat is installed the correct way. I actually used the old one for a minute cause I thought the new one was defective. Same result.
Part # THM 546095
Product line : NAPA thermostat, 195°

Never touch the timing belt.

No blockage in front of radiator.

Overflow is connected & not leaking.

I did burp the system.

No clue about the radiator cap. Could this actually cause overheating?

 

[JPNinPA]

Not timing belt but the fan/serpentine belt.

Rad cap can cause boiling/overheating. For example a 18 lb cap allows the pressure to build to 18 lbs. this increases the boiling point of water from 212 to 235 deg. When water boils it expands and gas bubbles form. As you know gas or air in the system causes more flow issues and more.

If you take the old and new thermostat in a pot of hot water and take note if one opens more than the other or if the opening is smaller on one than the other.

 

[JPNinPA]

Other things that will heat the engine while running above idle.
Blocked exhaust. Or CAT
Exhaust leak near engine
Running lean


If your radiator. Is not stock it may have a different cooling capacity. Either fin density or air flow.

At 35 mph or greater there is enough force on the radiator to sufficiently cool that an thermo switched fan will not come on. Go below 35 and it will.