Date: Tue, 19 Jul 2011 08:48:53 -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: <20110719112235.EXPB5.1119619.imail@eastrmwml46>
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Great questions.
On Tue, 2011-07-19 at 10:22 -0500, mcneely4@cox.net wrote:
> Mr. Squirrel, I believe that you have a tencentlife oil cooler
> installed as well. Is that correct?
Yep.
> I would expect oil temperature
> to run closer to coolant temperature with the external cooler than
> without, under load or at high ambient temperatures. An engine oil
> temperature of 200 F seems reasonable to me. I would expect that
> without the cooler, it might be climbing to more like 220 or even
> higher. I assume you have the stock thermostat, rather than a
> slightly cooler one.
The cooler one. It will be swapped out as we near winter to the hotter
one. (Others: this is a red herring, don't get sidetracked into cool v
hot thermostat discussion, it's been discussed here before.)
>
> How does your oil pressure respond to the conditions you describe
> below? That is, does the oil pressure drop when you put the extra
> load on and the oil temperature increases above coolant temperature?
Yep, just now looking to see and understand the correlation between oil
temp and oil pressure.
> If it drops, does it drop to a level that would be undesirable?
> When you are at load, and drop back to idle, what happens to oil pressure
> -- how low does it go?
Um, not exactly sure yet. New to this setup. After pushing along the
highway and seeing oil temp go up while coolant stay constant, I exited
the highway and drove about a mile before having to stop while a flagger
held back traffic through a construction site. Oil temp went down to
"normal" (i.e., not elevated) while waiting, oil pressure, which might
have been around 20 psi? 25? rose up a bit as the oil thickened. At no
time have I seen pressure go very low. Whatever that is -- what is a
minimum that one should watch out for?
Thanks!
-- RJS
>
> Thanks, mcneely
>
> ---- Rocket J Squirrel <camping.elliott@GMAIL.COM> wrote:
> > I just completed the wiring to my swell new gauge cluster: oil pressure,
> > oil temp, ATF temp (okay, not yet hooked up), engine/cabin battery volts
> > (they are on separate charging systems so being an electrical geek I
> > like to be able to monitor them both), and tach).
> >
> > This will be the first time I've ever had a vehicle with an oil temp
> > gauge!
> >
> > So I'm watching the gauge to learn how oil temp responds to driving
> > conditions. Once the little thermostat thingy in the oil filter banjo
> > adapter's bypass opens up and oil starts being sent to the heat
> > exchanger, the gauge rises up to about 180-185F and pretty much stays
> > there under light town driving. The coolant temp gauge in the van's
> > instrument panel shows a steady temp, too.
> >
> > So last week I'm heading out of town on the highway, up a grade, into a
> > headwind, and pushing pretty hard. Excited to be going on a camping trip
> > to a new site.
> >
> > What I saw was that while coolant temp continued to stay constant, oil
> > temp went up -- 195, 200F. The engine's working harder, okay. But here
> > the coolant temp gauge says that the cooling system is keeping up with
> > the demand while the oil temp says otherwise.
> >
> > Obviously, then, the senders for the two temp gauges are seeing things
> > differently.
> >
> > So here's what I'm thinking, correct me if I'm wrong:
> >
> > Oil temp and coolant temp decouple under high engine demand, and that
> > while the cooling system is capable of keeping the portions of the
> > engine that the coolant is in intimate contact with cooled, the oil is
> > in contact with portions of the engine that the coolant doesn't reach
> > and which are close to the combustion action.
> >
> > So where is this? My first guess is the heads. The coolant surrounds the
> > jugs, but not the heads, which are part of the combustion chamber and
> > where oil flows over the hot valve stems.
> >
> > The oil temp gauge reports the temperature of hot oil returning from the
> > heads mixed with general overall engine oil temp, so therefore it's not
> > an accurate indication of peak oil temp. And that's why people install
> > CHT gauges, to get a better picture of what's going on in the heads.
> >
> > This is my initial interpretation of what I'm seeing.
> >
> > --
> > Rocky J Squirrel (Jack Elliott)
> > '84 Westfalia: Mellow Yellow ("The Electrical Banana")
> > '74 Westrailia: (Ladybug Trailer company, San Juan Capistrano, Calif.)
> > Bend, OR
> > KG6RCR
>
> --
> David McNeely
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