My V6S has a coolant reservoir cap with pressure stated as 200kpa. This seems very high to me, compared to the 120 and 140 kph caps that Jaguar used to use on earlier engines. Is the higher pressure required by the supercharging? Would there be any detriment to using a lower pressure cap to relieve strain on the hoses and connections?
If a lower pressure cap could be used, can anyone suggest a part number?

 

First Law of Engineering: If it ain't broke, don't fix it.
Corollary: If it don't make it go faster, sound better or look better, don't do it.

 

I am merely speculating, I can't image this is because the engine is supercharged.
200kpa is 29psi, not sure if this means the system will necessarily operate at this pressure or that it will release if this pressure is reached.

I believe the primary effect of allowing the coolant to operate at above atmospheric pressure is to increase the boiling point

 

Well, yes, that is the reason for a pressurized system but does it need to be at 29 lbs per square inch? The common pressure for Jaguars used to be 16 lbs, and on earlier cars (such as my Mk 2) as low as 4, yes, 4 lbs.

And I do agree with the notion of leaving things alone if there no problem - but I am wondering about the long term effect of very high pressure on the plastic and rubber components in the cooling system.
It makes me a bit uncomfortable....
Thanks for these responses. Any other comments?

 

After reading further it seems there are a wide range of pressure ratings including 30psi 205Kpa.

Also relevant is the expansion tank cap pressure release performs a different purpose to previous generations of engines that had a radiator cap that released at a lower pressure to allow flow into the coolant expansion tank