[Healeys] BJ8 radiator cap issue

[Bob Spidell]

I don't believe the pressure will be higher with a 10lb cap. If the 7lb cap wasn't opening the 10lb cap won't either 
(except when you shut the engine off and 'latent' heat causes the coolant temp. to rise).

I don't believe the pressure cap is there to regulate pressure, only to provide a bit more margin from boiling, plus 
holding some pressure probably assists the pump and coolant circulation.

Bob


On 3/29/2013 7:33 AM, Oudesluys wrote:
> The higher pressure may perhaps affect the expanding of the bellows causing it to open at a higher temperature. This 
> may be why it is recommended that a 7lbs rad cap should be used.
> However I have known cars that did not have issues with a 10lbs cap.
> Kees Oudesluijs
>
>
> Op 29-3-2013 15:09, Bob Spidell schreef:
>> Doesn't make sense, at least according to the laws of physics I pretend to understand.
>>
>> If you didn't boil or lose coolant with a 7lb cap, it means you never reached 7lb. pressure in your cooling system.  
>> So the 10lb cap should never open, either.  The additional 3lbs pressure would only give a few more degrees before 
>> boiling, which doesn't appear to be an issue with your car (Law of Physics: the boiling point of a fluid is directly 
>> related to ambient pressure; that's why boiling cooks foods slower at higher altitude).
>>
>> IOW, the cap doesn't regulate pressure in the cooling system (like a voltage regulator)--it's there to keep your 
>> hoses, etc. from exploding if your engine overheats.
>>
>>
>> Bob
>>
>
>


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Bob Spidell           San Jose, CA            bspidell at comcast.net

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