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Date:         Tue, 10 May 2016 13:37:45 -1000
Reply-To:     Scott <SCOTTDANIEL@TURBOVANS.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Scott <SCOTTDANIEL@TURBOVANS.COM>
Subject:      Re: Filling the coolant reservoir...
Comments: To: John Rodgers <jrodgers113@gmail.com>
In-Reply-To:  <CA+az7_4QRMY=hivQnB0FC5+NdHnE=D44GVES40i3vb9LbFXthg@mail.gmail.com>
Content-Type: text/plain; charset=utf-8; format=flowed

Got yer Bentely Manual ? I'm sure in there it tells the release pressure of the Pressure Cap.In Bar and perhaps not psi.

I know it does for sure actually ...as the picture showing testing the pressure tester being used on the cap does not account for one or the other type of pressure caps used on Vanagons ..

the 82/83 Diesel Vanagon in North America uses a very ordinary looking 'traditional' cap .. common brand being Stant. Same basic design and type of cap used on almost all american cars for many decades .. like say 1956 Chevy ( my first car ) that cap would probably work.

the other type of cap is the blue cap .. I think Bentley shows testing one type but not the other.

naturally they have to mention the max pressure the cap is supposed to hold. I could look it up, it's around 13psi I think.

a 'long time' traditional automotive cooling system max pressure was 14 psi. Measured pressure on a cold engine is zero psi.

if you ever see a case where a van or car has been sitting a number of hours ..or overnight even, and you open the cap and there's still pressure .. that can only or most liikely be a head gasket issue in my mind .

Had a 1972 European model BMW 3.0 CS Coupe.. it did that for at least a year until I sold it. No other systems than that one. Normally .. a few hours of cooling down, there won't be any stored pressure . If there is, something is not really right.

ah yes..the old atmospheric pressure thing .. the diea that that's what really pushes air through an open intake valve and into the combustion chamber.. or coolant from the overflow bottle back to the pressure bottle through the Coolant Recovery Valve .

lol..as far as I'm concerned ...like in engine air intake ....the piston going down is SUCKing in air .. Sucking .. just like the cooling down coolant Sucks coolant back into the pressure bottle.

oh ...interesting idea. Read about a guy with a Subaru Engine Converstion ( would apply to stock vanagons just fine too ) that ran a Pressure Guage on his dash, connected to a coolant hose, so he could read in real time , in flight, his cooling system pressure.

once what normal is known.. this can be super useful. .if pressure goes down there is probably a leak ... if pressure starts getting abnormally high.. it's running extra hot pershaps ..or even combustion pressure getting into the cooling system .. which until one knows to recognize that situation..can appear as very mysterious overheating .. even intermittently.

Scott .

On 05/10/2016 12:56 PM, John Rodgers wrote: > > Anyone know the actual range of coolant system pressure our vanagons > run at. The coolant absolutely expands and contracts, as the engine > heats and cools, thus the need for the overflow tank. The overflow > tank is marked maximum and minimum when hot or cold, and the overflow > tank is vented on the top backside with three little holes to prevent > it from blowing out of something goes wrong in the system. But it > would be interesting to know what the actual system pressure range is, > especially since sea level atmospheric pressure is 14.7 psi. That > weight of air is enough to push the coolant back in to the system as > the coolant cools and shrinks. So what is actual system pressure at > both ends of the spectrum - hot and cold? > > John > > On May 10, 2016 17:30, "Scott" <SCOTTDANIEL@turbovans.com > <mailto:SCOTTDANIEL@turbovans.com>> wrote: > > perhaps have the guy google 'coolant recovery pressure cap for > automotive cooling systems, > > then maybe he'll believe coolant expands, such a cap accomodates > expansion by putting the 'extra' in overflow tank , then sucks it back > during cool-down. > > cars have used this basic system in one form or another since the > 70's , > even a little earlier. > > ( rather oddly, my 1985 Mercedes car still uses the old fashioned > system > ..the air space at the top of the rad is the expasnion zone for > coolant..no overflow / recovery tank. ) > > re last comment below .. > all cars have some form of a pressure relief cap. > Haven't heard of a totally closed one yet, > though modern car cooling system pressures can be quite high. > > here's a whole google search page the guy could read ...help him a > lot I > imagine. > > in one of those they mention 24psi for a more modern car. > Our vans run in the 13 or 14psi range max I believe. > > I have not found the blue caps to be extra reliable. I always carry a > spare. > for example... > saw one Subaru engine conversion with a head gasket issue .. > after problems with the first cap and pressure tank, > they put on a new blue cap and pressure bottle. > > pressure got so high...and the new blue cap did not release pressure, > that the pressure bottle puffed out like a football. > I still have it, it's only slightly warped where the level sensor > screws > in ... > so new I hate to just throw it in landfill. > > scott > > > On 04/26/2016 08:20 AM, Dan N wrote: > > Neil, > > he said that he gives room for the coolant to expand... I told > him when the > coolant expands the blue cap will open and the coolant goes to the > expansion tank behind the license plate... > > he didn't buy it... > > I am sure he's thinking as modern car with the radiator and a > filling tank > with no pressure cap and no expansion tank.. > > haha... > > :-) >


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