On Fri, Aug 27, 2010 at 8:36 PM, Michael Snow <slowmachine82@gmail.com> wrote:
> 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/
>

Sorry, I may be overstating the pressure here.  The system should
reach and stabilize at whatever nominal pressure that the cap is
designed for.  I see another note that it may be only 7 PSI for the
waterboxer.  If so, replace the 15 in my previous post with 7.

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