On Wed, 17 Sep 1997 09:37:19 -0700 Lane Rollins <laner@teleport.com>
writes:
>>..... 59 MGA...... convert it to a sealed system. ..... Does anyone
know the correct cap to use? .....
>
>How about something like this ..... expansion tank from a rubber bumper
car and run the over flow into it, then put at least say 7lb cap on it,
maybe 13lbs. It needs to be the cap for a B not the A, the lengths are
different Then replace the cap on top of your radiator with a blanking
cap like the one found on the top of a MGC.
BAD NEWS !!! Do not put a cap with pressure rating higher than 7psi on a
stock MGA radiator. The original radiator design will not accommodate
higher pressures. With a 13 psi cap it's pretty much guaranteed to split
the seams.
GOOD NEWS !!! A 50/50 solution of water and antifreeze and a 7 psi
pressure cap will keep it from boiling until it pegs the temperature
gauge, way past the 230 mark (speaking from experience). You don't need
pressure higher than 7 psi.
The MGA radiator filler neck is 1" deep, and the cap needs to have a
1-1/8" long reach on the plunger (1" when installed with the spring
compressed). MGBs and other later models have a 3/4" deep filler neck
and a cap with a 7/8" reach. If you install a short reach cap on a long
neck radiator you will have zero pressure.
The primary difference of a recovery type cap is the second seal at the
top rim of the filler neck. This allows the cap to hold a vacuum in the
neck to draw the coolant back into the radiator as the system cools down
and the fluid contracts. The original style cap has a large brass disk
just inside the top. The recovery cap will have a rubber seal around the
edge of that disk.
When you use a recovery cap on the radiator, the external tank is not
presurized, so any bottle will do. I prefer a clear plastic external
tank so I can see the fluid level without removing the cap.
A few years ago I had a radiator shop install a 3/4" deep filler neck on
my MGA radiator in place of the 1" deep part, so that I had a better
selection of caps available. Since then I have run across a 7psi coolant
recovery cap with the long reach at the local Giant Auto Parts store, so
the short neck conversion was not necessary.
Love this tech stuff,
Barney Gaylord
1958 MGA with an attitude
|