[Healeys] BJ8 radiator cap issue

[Oudesluys]

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
>
>
> On 3/29/2013 6:42 AM, Dan Stromquist wrote:
>> Water pump issue?
>>
>>
>>
>> Hi all, about 2 months ago there was a thread indicated that the correct
>> radiator cap for a BJ8 was a long neck 10 lb. cap.
>>
>> News to me but since a couple agreed, I ordered one to see if there 
>> would be
>> a difference.
>>
>> I have been running a 7 lb. cap with 180 degree sleeved thermostat. With
>> this setup, I've had an idle temp right at 180 degrees when warmed up.
>>
>> When I changed to the 10 lb. cap (with same thermostat) the BJ8 
>> immediately
>> ran 200 - 205 degrees at warm idle. Switching back to the 7 lb. cap 
>> brought
>> the idle temp right back down to 180 degrees.
>>
>> Why would this be?
>>
>> Randy
>>
>


-- 
Kees Oudesluijs
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