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Date:         Wed, 14 Apr 2010 18:53:29 -0500
Reply-To:     John Rodgers <inua@CHARTER.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         John Rodgers <inua@CHARTER.NET>
Subject:      Re: Expansion tank level; was RE: temp light blinking.
Comments: To: Robert Fisher <garciasghostvw@GMAIL.COM>
In-Reply-To:  <001b01cadc1d$a2fef2a0$e8fcd7e0$@com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

If I understand the operation of the cooling system correctly - on the later models with the 2.1L engines - there is a metal ring of tubing that goes around the engine compartment and coolant bleeds through the engine into this ring and back into the cooling system, removing air and providing some additional cooling by it's circulation. The air works through to the expansion tank with it's coolant level sensor and pressure cap, and any air is burped out through the cap to the overflow or coolant filler tank. Also, as the coolant heats it expands, forcing open the pressure cap, bleeding off excess coolant into the over flow tank. If there is too much coolant, the excess bleeds out through three bleeder holes in the top back side of the overflow tank and spills on the ground. These three little holes are the vents for the entire system. If you over fill either the expansion tank or the overflow tank, in either case the system will bleed to the ground through those three holes. If they are not plugged up, and the pressure cap works properly, there is no way to over fill either the expansion tank or the overflow tank.

A caution about thermostats. A thermostat can fail open - in which case the engine is difficult to get up to temperature: it can fail closed - in which case the engine can overheat even at idle: and the thermostat can fail partially open or become blocked so as to be only partially open - in which case, it will behave oddly like the temp gauge needle rising to just above the warning light, yet cooling back down when the heater is turned on. It may be worth the tame and expense to stick in another thermostat just to determine if that is the culprit or not.

John Rodgers Clayartist and Moldmaker 88'GL VW Bus Driver Chelsea, AL Http://www.moldhaus.com

Robert Fisher wrote: > --snip-- > Levels still full pressure tank , high as in up to filler cap in filling > reservoir > --snip-- > > This reminds me of a question I keep thinking of and forgetting to ask: > Where is full/normal on the expansion tank? I see a "min" mark just above > the mid-line seam, and I've always figured that the system was supposed to > be self-leveling to a point, but I have filled my expansion tank to the > bottom of the neck (with the overflow tank full to the bottom of its neck) > and the system always finds the same level, which is perhaps 1.5" above the > expansion tank seam. I have no leaks, no overheating issues or any of that, > so I'm just curious. My guess was that as it "self-bled" the air (how does > that air get out?)it made room for the coolant, but I dunno. Thoughts? > > Cya, > Robert > > >


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