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Date:         Thu, 27 Dec 2007 11:06:45 -0800
Reply-To:     Scott Daniel - Shazam <scottdaniel@TURBOVANS.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Scott Daniel - Shazam <scottdaniel@TURBOVANS.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="US-ASCII"

Your basic thinking sounds sound, lol. Or at least a good 'theory path' to pursue. What I would do is rig a switch such that you can trick the system from the cockpit, like take the idle switch out of the picture for long cold descents. Like if the idle switch is open, the ecu won't know it's a idle and above 1,500 rpm, and will continue operating the injectors a little. You could also try blocking off radiator air inlet, like all big trucks do in the winter. You should have your heater hoses insulated, and run the warmest thermostat you can find. Scott

-----Original Message----- From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Geza Polony Sent: Thursday, December 27, 2007 8:44 AM To: vanagon@GERRY.VANAGON.COM Subject: Overcooling Hypothesis--Long

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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