[Vwdiesel] '81 Rabbit overheating
Terry Briggs
vbriggs at stny.rr.com
Fri Dec 21 13:48:19 PST 2007
32psi pressure cap ! now that's a hot system lol , at 32psi, that means
276.76 degrees F that's what the temp of the steam it would produce
should it blow off {saturated steam temp}
On Dec 21, 2007, at 3:19 AM, James Hansen wrote:
> So THAT'S what those guys are doing chasing me around the racetrack- I
> have a 32 pound cap on my rad, and they are trying to certify my car
> as a pressure vessel...
> Good thing they can't catch me...
> -james
>
> Terry Briggs wrote:
>> The main reason for a 14psi cap is it stays below the 15psi limit of
>> a low pressure system, get over 15 psi and the whole system needs to
>> be certified as a pressure vessel . Our car cooling system is for a
>> lack of a better term, a low pressure boiler. if it weren't that way,
>> we could get some really good heat from our little diesels, then
>> again, if the system overheated, the resulting steam explosion would
>> most likely total the car I should think.
>> On Dec 20, 2007, at 5:36 AM, William J Toensing wrote:
>>> I thought I would wait to see if someone else would comment, but
>>> water boils at 212 F (100 C) at sea level. It boils at a lower
>>> temperature as altitude increases & air pressure decreases. As
>>> pressure increases, the boiling temperature increases. This is why
>>> modern cars use pressure radiator caps to increase normal operating
>>> temperature. This is why modern cars often use 14 pound pressure
>>> caps. Then the operating temperature can run much higher. This is
>>> why some temperature gages go up to 265 degrees F. There is a
>>> formula to figure how much the boiling point rises or lowers with a
>>> change in pressure, but I forget what it is.
>>> I would suggest adding a remote temperature sensing unit with a
>>> laser beam you can point at the part of the cooling system, engine,
>>> or other part you might want to measure the temperature of. I bought
>>> one at Costco a few years for around $50 as I recall. Auto parts
>>> houses should have them too. Radio Shack has a cheaper one without a
>>> laser pointer for less & they might have one with a laser pointer
>>> too.
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>>>
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>
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