400 radiator pressure cap

[RALPH M]

My 400/400 has an aluminium radiator with a 7psi cap Is this right and should the system be pressurised or simply have an overflow pipe attached. I understand the reason for pressurising but my car has a mechanical and electric fan, also an oil cooler.

Any thoughts?


Michael Ralph

[Geoff Dowdle]

Michael ,
The original 400 - 403 radiators were pressurized to about 2psi .
There is a ball and spring incorporated in the outlet of the overflow pipe .
I have recently fitted a new stronger stainless steel spring as a trial to my two 400s. My radiator pressure tester shows that they now run at approx. 8 - 9 psi .
At that pressure I have not encountered any problems, like leaks in the system .

So if your water pump, radiator hoses and other features of the cooling system are in good condition, I would not expect you to have issues with a 7 psi cap.
The alloy radiators I have heard are more efficient than the original brass type but they are known not lasts as long as the original type.

GeoffD

[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.

[RALPH M]

Thank you both. I was not aware of the original system that my 401 had and as my 400 has the ali rad and more modern cap I was curious. Always better to understand these things. The cooling sustem is working fine so apart from checking that the overflow pipe sits in liquid I will leave well alone.

regards

Michael