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Date:         Tue, 15 Aug 2000 22:31:33 -0500
Reply-To:     CHRIS STANN <cstann@home.com>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         CHRIS STANN <cstann@home.com>
Subject:      Re: idle before shut down [was wasserbox]
Comments: To: pokeswagon@blazenet.net
Content-Type: text/plain; charset="iso-8859-1"

I think the idle-down period is necessary after extended high-speed (75 MPH +) heats up the heads. Higher revs = more frequent combustion = higher amount of heat energy to dissipate. The coolant flows quickly and exchanges the heat efficiently, at the radiator end, keeping your water temps down. When you shut down the engine immediately the engine experiences what's referred to as 'heat soak' -- the coolant over the heads is no longer circulating and it begins to expand rapidly as it approaches boiling. This increases the pressure and pushes the coolant out into the overflow bottle which eventually overflows.

You would not necessarily experience this condition in city driving because you head temps stay lower. You water temps read higher because of lower engine revs, slower spinning water pump, and decreased air movement over the radiator. So, lower coolant temps at the sensor do not necessarily mean lower head temps or lower oil temps. In-town driving is harsher than highway driving, to a point, because of the constant rev changes and lower oil pressures while idling -- the engine cooling and oiling system do not operate at peak efficiency.

So, in highway-driving scenario the heat is not distributed very evenly. In town the heat is distributed more evenly because of a less-efficient cooling system, hence the higher water temp readings.

Does anyone have a head-temp sensor on their WBX motor?

----- Original Message ----- From: (Donna Cassano) <pokeswagon@blazenet.net> To: <vanagon@GERRY.VANAGON.COM> Sent: Tuesday, August 15, 2000 4:05 PM Subject: idle before shut down [was wasserbox]

> Mark Dorm wrote: > > > > > > > Isn't city driving the hardest with all its stop and go traffic??? ---- > > That's when my temp gauge starts to climb. > > > How many of you have been idleminuteing? > > Never have. Might have to try it. > > > >The manual specifies that after hard running you must let the engine idle > > >for a minute before shutting down. > > Boy, who'd a thunk it? What other little "tips" does VW offer in their manual? > > Peace - donna > '84 Westy (Pepe)


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