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Date:         Thu, 27 Dec 2007 14:12:06 -0800
Reply-To:     Michael Elliott <camping.elliott@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Michael Elliott <camping.elliott@GMAIL.COM>
Subject:      Re: Overcooling Hypothesis--Long
Comments: To: Geza Polony <gezapolony@SBCGLOBAL.NET>
In-Reply-To:  <vanagon%2007122711451825@GERRY.VANAGON.COM>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Darn you Geza! I just returned from my monthly mountain trip and experienced the overcooling which I had inquired about last month (see "Thar I was...") and suddenly the overhead cartoon light bulb lit and I knew exactly what was going on! I was going to post it this afternoon, and then saw your post. You beat me! You scum.

It's obvious: Thar I was this morning, at 7,000 feet, heading down in 22F weather in my 1.9L auto. A long downhill, initially dropping 3,000 feet in 8 miles. Foot's off the gas, transmission's engaged, engine speed above the 1,500 rpm point. Under these conditions, the ECU shuts off fuel. No fuel, no combustion; no combustion, no heat. Like, duh.

Obviously one can't put the van in neutral, not on these grades, unless one wants to bake the brakes. And blocking the radiator is pointless since the thermostat has presumably taken note of the coolness and has blocked radiator flow, as designed. No, the problem is a dead-cold engine with no means to keep itself warm.* No amount of radiator hose rerouting or thermostat trickery can make an engine which isn't burning any fuel stay warm.

============= * I noted the lack of warm water wasn't doing much to keep ME warm in the driver's seat, either!

-- Mike "Rocket J Squirrel" Elliott 71 Type 2: the Wonderbus 84 Westfalia: Mellow Yellow ("The Electrical Banana") 74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano KG6RCR

On 12/27/2007 8:43 AM Geza Polony wrote:

> I've been wondering about Vanagon Overcooling Syndrome for a long time now, > and just came up with an idea as I was going downhill in Northern California. > > Here's the syndrome: it's cold out, you're going downhill for a long ways, > and there is just nothing you can do to get the coolant warm. It's not a > gauge problem; the coolant really isn't warm, and your heaters don't work, > and the van runs bad. > > Must be a thermostat stuck open! you say; but no, at home doing the pot o' > water test, the tstat works perfectly. You put it back in; the van still > overcools. This cannot be; yet it is. > > Here's my idea. When you're coasting downhill, you're using the engine as a > brake. This means that above 1500 RPM, with the idle switch closed, the > engine isn't getting any gas, as the ECU has shut the injectors down. If it > isn't getting any gas, it also isn't producing any heat. The engine is > functioning as a brake, but there isn't any combustion, and so, after a > period of 10 minutes or so in freezing temperatures, the coolant loses > temperature, and your gauge is way off the edge of the scale. > > I tested this by going downhill, engine warm, and taking my foot off the gas > to coast. I could see the gauge move colder before my eyes. Give it a little > gas, and the engine warms up. This is kind of tricky from a driving > standpoint, but it works. > > I'm talking about an '84 1.9 with the twin switches on the throttle > body--maybe in later years VW corrected this with new switch type, maybe a > remap of the ECU? > > Anyway, such is my thinking. Anyone who has experienced this knows it is a > real problem in the winter months. Hope this helps.


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