My 2c. :)
>From literature I have read, the purpose of the Recovery cap is to prevent
the possibility of the cap sucking air from atmosphere from around the top
of the cap when the cap 'recovers'. It is simply an additional, thick (grey
rubber in Aussie cases) air tight seal that _ensures that all air is sucked
via the exit tube when the cap closes. I have a recovery cap and a stock
cap. On my A the recovery cap works all the time. In my experience on my
car, the stock cap does not recover completely and the system ends up with
lowering volumes of water in the rad. and increasing volumes in the recovery
tank. The stock cap does recover to a certain extent but not completely in
my experience with my radiator and the radiator cap I tested with. I have
measured this by marking the tank levels & substituting caps.
The caps are exactly the same price whether or not they are fitted with this
extra seal so FWIW I chose the recovery cap.
Either way a recovery system is a great thing to have IMO. It has made life
a lot easier for me here in hot Australia. I don't have to worry so much on
a very hot day / long trip. That extra piece of mind is worth the $20-$30 or
so it costs to fit one up. Try it with the stock cap, if it works great - no
need to change out your existing one. I guess it largely depends on the
quality of the seal, rad surface-cap surface.
Cheers,
Neil
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