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Date:         Tue, 23 Jul 2013 12:23:03 -0400
Reply-To:     Stuart Fedak <ve3smf@YAHOO.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Stuart Fedak <ve3smf@YAHOO.COM>
Subject:      Re: Coolant Reservoir Boiling
Comments: To: Steve <loudmouth_70@YAHOO.COM>
In-Reply-To:  <1374551096.72767.YahooMailNeo@web142603.mail.bf1.yahoo.com>
Content-Type: text/plain; charset=us-ascii

The cooling system on a vehicle uses increased pressure in the system to get boiling point elevation. What this means is water at standard conditions of pressure will boil at 100 degrees Centigrade. When you gain elevation, you get boiling point depression, which is why water will boil at a lower temperature at higher elevation. By having the system operate at increased pressure, the engine coolant is able to absorb more heat, before it will reach boil point and turn into vapour.

When you have a faulty reservoir cap that will open up at a lower pressure (or a leak), you will get boiling at a lower temperature. It does not mean that the temperature of the coolant fluid is higher, it just means at that temperature and pressure, it will turn into vapour = boil . You start to loose engine coolant. There will be less coolant to cool the engine, and eventually the coolant will all escape, and the engine temperature will increase.

Just because the coolant temperature had not gone up, just means you saw the coolant leak and boiling before significant coolant fluid was lost.

The temperature gauge is engineered to assume (and is calibrated to show) when the system is operating under increased pressure. I hope this explanation helps, and does not just add to the confusion.

The physics behind pressure and temperature elevation before boiling is why people use pressure cookers for cooking, autoclaves for heat sterilization and cooling of engines.

Cheers! Stuart

Sent from my electronic umbilicus

On 2013-07-22, at 11:44 PM, Steve <loudmouth_70@YAHOO.COM> wrote:

> Dear List, > > It's odd that my temperature gauge wasn't showing signs of overheating. First saw the leak in the back after I pulled in the driveway; the coolant reservoir of my 82 1.9l diesel was boiling over. Checked the fuse for the fan, although i can't remember hearing it lately, the fuse looked good. Not sure what the next step is. > > I may be looking for a silver lining--the weather in Seattle is amazing this time of year, usually don't get to work on this baby without the rain. Feeling fortunate. > > > Seattle > 82 Diesel > > Weekender Package > > Seattle, WA


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