On Fri, Aug 27, 2010 at 12:31 PM, Marius Strom <marstrom@microsoft.com> wrote:
> I believe the cooling system is rated for a max of 15 PSI.
>
> I'm curious, though, under what general conditions are you likely to achieve max pressure in this sealed system? �I can think of a few variables:
>
> 1) as temperature increases, pressure should increase as well (however, the overflow pressure cap is what limits this to 15 PSI)
> 2) as water pump speed increases, there should be some increases in localized pressure (however, the overall system pressure should stay about the same - it's a sealed system, after all)
>
> What's the hive-mind say about this? �If my thermostat housing drips a little bit at 15 PSI, but holds fine at 13 PSI, when am I likely to experience those last few bits of pressure? �(Side note: I'm replacing my thermostat housing this weekend, but I assume the problem will just move to the next weakest link in the chain :)
>

A properly-sealed cooling system reaches approximately 15 PSI on every
drive that is sufficiently long to heat the engine and coolant to full
operating temperature.  If it were not so, the overflow tank (behind
license plate) would be unnecessary.  The worst-case scenario is when
the pressure-relief valve fails in the closed position and the cooling
system sees much more than 15 PSI.  You'll find out quickly which hose
or clamp is the weakest link if this goes on for very long.  I've
never see a clamp fail, but seen plenty of hose ruptures.

-- 
Michael Snow
1987 Syncro TiiCo
1982 Westfalia 1.9TD
http://slowmachine82.blogspot.com/