Expansion Tank Cap Question

[sfdaytona]

I couldn't find anything related to my question in the search, so here goes:

I've been wrenching on my own stuff for decades, and assumed all cooling system caps had a 14-16psi max rating. I recently did a full on cooling system overhaul on my 2011 LR4, which included a new cap for the expansion tank, which is 200kpa, or 29psi. Anyone have some insight as to why 29psi is necessary? Just curious. That number seems pretty high to me.

Thanks,
Nick

 

[ktm525]

The 29 is to make sure the coolant crossovers rupture.

 

[sfdaytona]

The 29 is to make sure the coolant crossovers rupture.

That was my first thought, haha.

 

[Stuart Barnes]

Higher pressure raises the boiling point of the coolant. This enables the operating temperature of the engine to be higher and because of the dark arts of thermodynamics that results in a higher thermal efficiency.

Obviously that’s a very boiled down version. Ha.

Stu.

 

[Stuart Barnes]

And for those interested.

https://durathermfluids.com/pdf/techpapers/pressure-boiling-point.pdf