I never understood the need for an overflow bottle. If you read the
owner/shop manual on any "pre-overflow-bottle" car, you will discover that
the radiator itself has a fill line or at least a spec about the fill level.
In other words the very top of the radiator is supposed to be empty. The top
of the radiator itself is the "overflow bottle".
Perhaps too many people were blindly filling their radiators to the very
top. The government decided to put the fill line "in your face" with the
overflow bottle. Of course you can still fill the overflow bottle to the
top. Then you need an overflow bottle for the overflow bottle ;-)
I bet the auto makers are just thrilled about the overflow bottle
requirement. They really needed something to fill the vast void under the
hood of the modern car ;-)
Bob Donahue (Still Stuck in the '50s)
Email - bobmgtd@comcast.net
Cars: 52 MGTD - #17639
71 MGB - #GHN5UB254361
Member: NEMGTR #11470
NAMGBR # 7-3336
Hoosier MGB Club
Olde Octagons of Indiana
----- Original Message -----
From: "Denise Thorpe" <xyzabcde@earthlink.net>
To: <mgs@autox.team.net>
Sent: Tuesday, March 10, 2009 9:12 PM
Subject: Re: [Mgs] Flushing the cooling system?
> Hi Paul,
>
> Since my last pontificating went over so well, I'll do it again. A
> radiator boils over when the coolant increases in volume to the point that
> the pressure overcomes the pressure limit of the radiator cap...something
> about PV=nRT. If a car has an overflow bottle, like a late model B, the
> air in the bottle is displaced and absorbs the extra volume so the coolant
> never boils over. That's why there's an upper limit on filling the
> bottle. Early Bs have an overflow tube so that extra volume is dumped on
> the ground before it has a chance to bypass the radiator cap. The problem
> with this is that the coolant is then gone for good and doesn't get sucked
> back in like it would if it went into a bottle. So to answer your
> question, Bs with the correct parts should never boil over.
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