[Vwdiesel] '81 Rabbit overheating

[Stephen Kraus]

What if you have slight pressure in the system?

On Dec 20, 2007 4:23 PM, Roger Brown <r.c.brown at ieee.org> wrote:

> Rolf Pechukas 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.
> >
> > yeah, but my system for whatever reason is not pressurizing
> > hence my concern about approaching 200+°f
> >
> > Rolf in MA
>
> No pressure in the system is a good thing, as far a negative sign of a
> leaking head
> gasket.  Coolant must exceed the boiling point to cause a pressure rise
> (due to the vapor
> pressure).  With a mix of glycol and water, the BP is probably up in the
> 230-240F range,
> depending on the mix you are running (plain water is 212F at sea level,
> but add antifreeze
> and that rises a fair amount).
>
> --
>
>   Roger
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