400 radiator pressure cap

[innellan House]

https://liquidintelligence.com.au/pr...diator-coolant

Michael,
the Marston Excelsior unit has a spring loaded ball which passes steam and more importantly, prevents the ingestion of air as the radiator cools. In the absence of this valve the tip of your overflow pipe needs to be submerged to reduce coolant loss and to prevent air pocketing.
The original low/no pressure radiator does an adequate job of cooling in hot, humid Queensland.
The soluble oil coolant product is touted to boil at 115 degrees centigrade at one atmosphere.
sincerely,
vincent.