I have a peculiar overheating issue that is perplexing both myself and my mechanic. No amount of googling and scouring forums has given any answers.
Here’s the details:
2011 JK 3.8L A/T
320k km
Temp gauge and obd scan show overheating shortly after cold start — engine gets up to temp, then continues to heat past 216° (highest I’ve seen it was about 235).
Turning the engine off for a few moments then back on, the temp drops to normal. It will stay fine until it the engine is off long enough for it to cool completely, even after long days of driving.
When it’s overheating, the rad and upper hose are completely cold still. After turning off, you can feel the rad and upper hose heat up as thermostat opens and fluid flows.
Why I don’t think it’s the thermostat: Current thermostat was only a year old. We replaced it with Mopar OEM and issue has remained.
Why I don’t think it’s the water pump: Water pump is only 6mo old, and there would be other symptoms beyond the cold start.
Why I don’t think it’s the temp sensor: Replaced with Mopar oem; no change to issue.
Why I don't think it's the fan: Fan appears to be turning on at correct times.
Why I don’t think it’s air-lock: (my original suspicion, and the one that still makes the most sense): Mechanic vacuum filled with coolant when replacing the thermostat. I have also burped it since, and it has not solved the problem. No sign/smell of coolant leaking anywhere.
Why I don’t think it’s a head gasket: Mechanic has tested for this. Tests showed no problems.
Why I don’t think it’s intake manifolds: These gaskets were replaced 6mo ago.
Why I don’t think it’s the rad: Was replaced 2mo ago. Problem started shortly after this, so it could be related, but doesn’t really make sense that it would only be a problem at cold start, or why turning engine off would instantly resolve it. Rad cap is the newer Mopar replacement (with the plastic outer).
There are probably a few other things I have read but none of them make sense with the problem only occurring when it does, and how quickly it resolves after turning engine off.
I have had issues with the coolant system leaking since I bought this thing at 250k km — leaks, blocked heater cores, 3 new rads. But the big overhaul I did early this year doing the intake manifold gaskets, timing cover, water pump, etc etc seemed to have cleared all that up. Really just have no idea at this point.
Any thoughts?
Here’s the details:
2011 JK 3.8L A/T
320k km
Temp gauge and obd scan show overheating shortly after cold start — engine gets up to temp, then continues to heat past 216° (highest I’ve seen it was about 235).
Turning the engine off for a few moments then back on, the temp drops to normal. It will stay fine until it the engine is off long enough for it to cool completely, even after long days of driving.
When it’s overheating, the rad and upper hose are completely cold still. After turning off, you can feel the rad and upper hose heat up as thermostat opens and fluid flows.
Why I don’t think it’s the thermostat: Current thermostat was only a year old. We replaced it with Mopar OEM and issue has remained.
Why I don’t think it’s the water pump: Water pump is only 6mo old, and there would be other symptoms beyond the cold start.
Why I don’t think it’s the temp sensor: Replaced with Mopar oem; no change to issue.
Why I don't think it's the fan: Fan appears to be turning on at correct times.
Why I don’t think it’s air-lock: (my original suspicion, and the one that still makes the most sense): Mechanic vacuum filled with coolant when replacing the thermostat. I have also burped it since, and it has not solved the problem. No sign/smell of coolant leaking anywhere.
Why I don’t think it’s a head gasket: Mechanic has tested for this. Tests showed no problems.
Why I don’t think it’s intake manifolds: These gaskets were replaced 6mo ago.
Why I don’t think it’s the rad: Was replaced 2mo ago. Problem started shortly after this, so it could be related, but doesn’t really make sense that it would only be a problem at cold start, or why turning engine off would instantly resolve it. Rad cap is the newer Mopar replacement (with the plastic outer).
There are probably a few other things I have read but none of them make sense with the problem only occurring when it does, and how quickly it resolves after turning engine off.
I have had issues with the coolant system leaking since I bought this thing at 250k km — leaks, blocked heater cores, 3 new rads. But the big overhaul I did early this year doing the intake manifold gaskets, timing cover, water pump, etc etc seemed to have cleared all that up. Really just have no idea at this point.
Any thoughts?
