XJ coolant overflow after engine is shut off

[JMA_2001XJ]

Have you assessed whether there is any correlation to the kinds of driving being done before parking? Or whether it correlates to parking over a cooler area (garage) or over hot asphalt? Have you check the boiling point of your coolant? I guess you still haven't tried a different cap?

No correlation. I drive pretty consistent. Not aggressive at all, this is not the vehicle for that. It has only happened over asphalt. Still no new cap because the system was showing a lack of being able to hold pressure when the test cap with gauge was on. The cap was replaced 6 months ago with an OEM one.

 

[JMA_2001XJ]

I had the same issue in NY in the summer a few years ago, I replaced the fan clutch and it solved the issue. Even though it spins it doesn't mean it's okay.

The mechanical fan works as it should.

 

[rtolboom]

The cooling liquid is not circulating after you turn off the engine. Could it be that the liquid starts to boiling because of the hot engine? The question is - why is it boiling? I have watched the one of the Youtube video's of Chris Fix. He shows that water starts boiling at a lower temperature than a mixture of ethylene glycol and water. Could it be that there is too much water in your mixture?

 

[rtolboom]

here is the video, see 01:25: https://www.youtube.com/watch?v=29z94xBdAjE

 

[maxbraketorque]

The cooling liquid is not circulating after you turn off the engine. Could it be that the liquid starts to boiling because of the hot engine? The question is - why is it boiling? I have watched the one of the Youtube video's of Chris Fix. He shows that water starts boiling at a lower temperature than a mixture of ethylene glycol and water. Could it be that there is too much water in your mixture?

I don't think there is any magic about still coolant boiling below its rated boiling point. Water can boil after shutdown if a large fraction of the engine block is sitting at a temperature significantly above the boiling temperature of the coolant. And the 4L block has a lot of iron that can be toasty, especially around the exhaust passages. I could imagine that heat could flow from the exhaust manifold into the head.

 

[XJI6191]

(1) a function of anti-freeze is to raise the boiling point of the coolant above 212*
(2) temperature of coolant increases when the engine is turned off, because there is no airflow thru' the rad. (which is why some electric fans are designed to continue running after the car stops, indeed some have been known to cut in after the car's parked & the driver is walking away)