you're on the right track Jack.

for this time of year, the cooler t-stat is just perfect.

you stand to go through all kinds of mess and trouble for no real gain right
now if you change our your cooler t-stat.
Wait till fall..
then install the hotter one.
Have a cool one instead, or whatever your pleasure is.

and ..seriously............there really are times when it is WAY smarter to
leave 'well enough alone'.

Man , if I had  a dollar for every time something on a car or vanagon was
about 95 % perfect, and I thought..well, just this one little tweak or
operation and it'll be 100% ..
and then I lost ground ...or it didn't make it any better..
and I WISHED I had left it alone ...I'd be much richer , or much less poor,
than I am !!

I think you are just fine as is. Really.
Scott

----- Original Message -----
From: "Rocket J Squirrel" <camping.elliott@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Saturday, June 04, 2011 6:53 AM
Subject: Re: Thermostats [Was: Spooked!]

> Thanks for the deeper explanation of how the system works.
>
> I understood that the thermostat isn't a binary on-off thingy, but a
> device that gradually opens once we hit the bottom end of its range.
> Scott said he didn't like the low-temp ones in winter, and what I was
> questioning was whether that made any especial difference, since
> regardless of whether it's cold or hot outside, the engine will get
> hotter and hotter until it reaches the bottom end of the t-stat's range
> and the t-stat will then work to keep the engine within its control
> range.
>
> IOW, season does not make a difference?
>
> PS. Thing I've learned is to not disregard Scott's words, but I do like
> to look at them more deeply.
>
> PPS. I think the arguments here in favor of the stock t-stat are good
> ones, and if changing the t-stat was super easy I'd do it in a
> heartbeat. But I somehow sense that we're talking a lot of coolant loss
> in the process, and a messy driveway, and buckets of coolant to somehow
> dispose of. Not to mention the whole gosh-darn cooling system filling
> and bleeding rigamarole.
>
> On Sat, 2011-06-04 at 01:36 -0400, David Beierl wrote:
>
>> At 12:47 AM 6/4/2011, Rocket J Squirrel wrote:
>> >Winter or summer, the thermostat will pretty much bring the engine up to
>> >80C (or 87C, depending its setpoint), yes?
>> >
>> >Seems to me that regardless of whether there is snow on the ground or
>> >molten asphalt, the engine will just get hotter and hotter until the
>> >thermostat cracks open, and it's the thermostat's job to modulate the
>> >amount of water going to the rad to keep the coolant -- at the point
>> >where the thermostat senses it -- at the setpoint temperature.
>>
>> It isn't a setpoint so much as a balance - the 'stat opens over a
>> range of about 35F, so while you're in the control range of the
>> system the temperature at the thermostat will be between ~185F and
>> 220F.  The fan will be running at high speed ~ten degrees before the
>> thermostat is fully open.
>>
>> Once you hit 220F you're now dependent on the ability of the
>> radiator/fan to reject heat so you've got a new balance between 220F
>> and the system boiling point, which should be close to 260F if you're
>> running 50/50 ethylene-glycol coolant and your pressure cap is in
>> good shape (265F at 15 psi, I think our caps are 13 psi).  It's still
>> a balance because heat transfer goes up with the square of
>> temperature difference.*
>>
>> Somewhere at the top of that range you'll notice a little red light
>> blinking on your temp gauge, and VW specifically says (owners manual,
>> page 37 in the '89 book) that elevated gauge temps are "not serious"
>> until the light starts blinking.  According to "some antifreeze mfr"
>> 260F is a common setpoint for engine overheat alarms.
>>
>> *this margin between 220F and boiling point decreases at altitude,
>> since it's absolute pressure and not gauge pressure that really
>> matters...
>>
>> "Open-deck" engines like the Subaru (according to the Subaruvanagon
>> list folks) are not so tolerant of temperature excursions, so the
>> Subaru cooling system is regulated a good deal more tightly than the
>> WBX  in normal operation.  It still has the same margins at the
>> extremes, but the thermostat system works more crisply.
>>
>> Yrs,
>> d
>>