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Re: aluminiun corrosion

henri baccouche <[email protected]> wrote:

>My experience with 10 year old vw/ audi/bmw cars has been that 
>the aluminium heads show much more corrosion  than the aluminiun 
>radiators . I figure that the electrolysis sets up between the
>nearest electrodes (alum head to iron block) and this is why the
>radiator does not corrode as severely as the heads.
>
What also adds to this phenomena is the fact that heads are made
of Cast aluminium and radiators are made from Extruded aluminium.

Extruded aluminium is more dense, has a smoother surface and useually
comes with some sort of protective finish (anodizing, etc.).

Note that this "electrolysis" does take place between the the engine
and the radiator and causes your radiator hoses to brake down from
the inside out. So even though your hoses 'look' good they may actually
be in poor condition. To check this, with the engine cold and the radiator
cap off. Squeeze each hose in different places and feel for soft or
hard spots and/or the sound of the reinforcing coards cracking.
The next time you have the cooling system drained, clean out the hoses
and look inside for cracks and/or erosion of the inside surface.


Hope this helps,

Shawn...
[email protected]

'83 BMW 320is (E21)
BMW CCA Member - Boston Chapter