Date: Wed, 20 Jul 2011 10:27:52 -0700
Reply-To: Rocket J Squirrel <camping.elliott@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Rocket J Squirrel <camping.elliott@GMAIL.COM>
Subject: Re: Watching Oil Temp (long, as usual)
In-Reply-To: <CACGkSd2uLGoW4X8A293YZjXPpy-OKqm4gdoL485=5U0pv51Mbw@mail.gmail.com>
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"Airstream," he said.
Like crawling up a desert grade in 1st gear (AT) at 20 mph in 100 degree
F weather.
On Wed, 2011-07-20 at 10:13 -0700, Jake de Villiers wrote:
> There's some almost information in your post Mike.
>
> The oil pump moves the oil at a fixed rate whether cold or hot. Just
> like your water pump, it increases the rate with RPMs.
>
> The sump, whether your finned aluminium VW one or my black painted
> steel Subaru one is hanging down in the airstream for a reason. The
> cooling air pulls heat from the metal surface, allowing the heat from
> the oil to take its place.
>
> And yeah, the volume of coolant vs the volume of oil makes the temp
> gauge cycles very different from one another.
>
> Happy motoring!
>
>
>
>
>
> On Wed, Jul 20, 2011 at 9:10 AM, Rocket J Squirrel
> <camping.elliott@gmail.com> wrote:
>
> On Wed, 2011-07-20 at 08:47 -0500, Dave Mcneely wrote:
>
> > Bottom line, I think the oil has a major heat source, and
> only if an
> > external cooler has been added does it have a real
> functional way to
> > dissipate heat other than to the coolant through metals
> that both
> > contact and through such things as the sump. The sump is
> like a
> > reservoir of liquid, it cools slowly compared to a
> radiator. The
> > coolant has a large heat sink, and thus has a temperature
> gradient.
> > That gradient includes the oil.
>
>
>
> So what we're saying is that the oil is in contact with some
> really hot
> bits, and because there is high thermal resistance between the
> oil and
> the coolant, the oil can climb to much higher temperatures
> than the
> coolant.
>
> It doesn't help matters that the hot oil drains down to the
> sump which
> isn't cooled by anything except the hot pavement under the
> engine!
>
> Others have also explained that while the water pump can move
> a lot of
> coolant up to the heat sink in the front, the little oil pump
> just chugs
> along pushing the oil more slowly and in lower volume so that
> even if
> there was an external oil cooler the size of the radiator, the
> stuff
> ain't moving fast enough or in enough volume to cool the
> really hot bits
> it's in contact with like the coolant can for the hot bits it
> is in
> contact with.
>
> I think I've arrived at point where I have a better
> understanding of why
> the oil temp gauge shows higher peak temps during high engine
> demand
> than the coolant gauge shows -- which is the answer to my
> original
> question! Many thanks to all who have taken the time to
> respond to my
> inquiry!
>
> -- RJS
>
>
>
>
> --
> Jake
>
> 1984 Vanagon GL 1.9 WBX - 'The Grey Van'
> 1986 Westy Weekender/2.5 SOHC Subie - 'Dixie'
>
> Crescent Beach, BC
>
> www.thebassspa.com
> www.crescentbeachguitar.com
> http://subyjake.googlepages.com/mydixiedarlin%27
>
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