Hi Colin,
The problem with overflow bottles is that most are just that...they
catch the overflow. However, there is a better solution, imho.
In the 1960's, same era as most of our cars, certain Volvo models (6
cyls and some 4's) carried a plastic bottle which appeared to be an
overflow bottle, but was actually a functioning part of the cooling
system (unlike 98% of similar looking bottles on other cars). The rad
was sealed except for the "overflow pipe" which went from the top of the
rad to the bottom of the bottle. The top of the bottle is flat and has a
screw top...the same screw top that most rads have, so the rad cap goes
there. As such, the water level in the system can be monitored by
observing the level in the bottle. Once the system is set up, normal
levels in the bottle are approx 1/4 full when cold, and 2/.3 or so full
at operating temp. You must remember to replace the normal rad cap with
one which seals tightly so that the pressure is controlled from the
bottle.
On first filling after installation, the system gets rid of all its air
out through the bottle, and sucks good coolant back on the next cooling.
You must consequently top up for a couple of cycles before stability is
reached. When working correctly, it virtually guarantees a completely
full cooling system.
I have got a couple of these bottles from wreckers yards, and have used
this system on a number of cars, and it worked every time. Latest was a
36 Packard, with the added benefit that I can now lightly pressurize the
system (4psi cap), and the car doesn't boil over any more on hot, slow
days.
Hope this is clear.
John Slade
Manotick, ON
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