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Date:         Thu, 18 May 2006 00:47:06 -0400
Reply-To:     Dennis Haynes <dhaynes@OPTONLINE.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Dennis Haynes <dhaynes@OPTONLINE.NET>
Subject:      Re: maybe too much information is worse...
In-Reply-To:  <000001c67a33$5b943c40$6400a8c0@masterpc>
Content-type: text/plain; charset=us-ascii

One more thing!

You need to correct that coolant boiling after shutdown problem. First guess is bad pressure cap. Replace it ASAP. The bubbling thing is not good. Also, after a high speed or under load run, allow the engine to idle down for few minutes before shutting it off. This may sound counter productive as the temp gauge may rise waiting for the fan to turn on but is beneficial. Under load, many parts will get much hotter than the bulk coolant temp. 600F pistons, 400F parts of heads, 250 oil, etc. shut off the engine, now the coolant stops flowing and these hot parts have no place to get rid of that heat. Oh, those poor rubber head gaskets and lets burn that oil onto the top rings and maybe leave a hot valve open so it can warp a little. Yea, I'm exaggerating but a cool down period really is a good thing, especially after pedal to the metal driving.

Dennis

-----Original Message----- From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Dennis Haynes Sent: Thursday, May 18, 2006 12:27 AM To: vanagon@GERRY.VANAGON.COM Subject: Re: maybe too much information is worse...

-----Original Message----- From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of John Bange Sent: Wednesday, May 17, 2006 8:40 PM To: vanagon@GERRY.VANAGON.COM Subject: Re: maybe too much information is worse...

On 5/15/06, Dennis Haynes <dhaynes@optonline.net> wrote: > > Where is the oil temp sensor located? Is it really seeing oil temp or case > and some other temps? I would be concerned about the oil pressure though. 28 > psi ( 2 Bar) at 4,000 rpm is a minimum. a a healthy engine should be able to > maintain almost 10 psi/1,000 rpm except under extreme conditions.

Oil temp sensor is just the simple drain plug replacement type. I reckon the bottom of the sump there ought to be seeing actual oil temps, no?

Engine oil is actually a lousy conductor of heat, in fact, oil is an insulator. The oil on the bottom will "skin" and a layer will not move. Air flow over the sump will also contribute to the case being cooler that the oil in it. The drain plug sensor will give a good indication but the actual oil temps may be 10-20F higher.

The 20+psi was at 3000rpm or so, and I'd say that grinding up the grade out of Baker, CA in 109F heat to be pretty extreme conditions.

As long as the radiator can keep up, the outside temp will have limited effect on oil temp. The oil to water heat exchanger does a good job until the thermal load on the oil exceeds its capacity. Then oil temp can sky rocket.

For the "10psi per1Krpm", what grade of oil is that?

10 psi/1,000 rpm is a general guide line for any engine. If that can't be maintained, oil viscosity is the first thing to consider. The Vanagon engine is a low tolerance, (sloppy) engine further compounded by an engine case that expands and lets the bearings get loose along with an oil pump design that is extremely viscosity dependant. The pump can actually stop pumping if the oil gets thin enough. The owners manual calls for 20w-50 for most climates and even recommends straight 40 for the tropics. With today's multi-weights, the 20w-50 or synthetic equivalent is better than the straight 40.

I reckon 10w30 would be like water at 220F. I put in a mix of 5w15 and 10w30 syntetic for the trip in anticipation of the heat. I watered down the straight 15w50 because I was seeing something like 75psi+ cold.

Again, modern oils are highly engineered products-that work. Mixing different viscosity multi weights can make a real mess. There is nothing wrong with 75 psi on a cold engine. A few minutes will take care of that anyway. Just drive gently and avoid high revs until the temp gauge clears the white bar. Before the inline engines had hydraulic lifters, those engine ran at 90 psi hot! I would not worry about excessive oil pressure until you 100-125 and still climbing which would also indicate a relief valve problem. The Mobil 15w-50 is rated to flow down to -35F. I have used it as low as -4F. In regular weather below the 20's I would use a 0w-40, (Mobil 1 European car formulae) or 10w-40, (Mobil 1 extended performance). BTW, oil analysis is indication that a 7,500 mile change interval is the reasonable limit for the Water boxer. Even the synthetic is suffering from oxidation and nitration, most likely due to high upper ring temperatures.

At any rate, I'm now at Bryce Canyon scabbing off their wireless internet at the gerneral store. Van made it up to 8000ft jst fine, though the coolant has a tendency to boil like crazy when I shut the engine down, and a big piece of the horsepower seems to have stayed behind in Zion where it's only 4000ft...

A normally aspirated engine will lose 3%/1,000 ft altitude.

Enjoy your trip!

Dennis -- John Bange '90 Vanagon - "Geldsauger"


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