[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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