recommend putting a thin film of the blue RTV on the O-ring.  This acts
as
cement to hold the O-ring in place while you are installing the pump
(they
fall out of that groove pretty easy otherwise) and also seals any
irregularities that might be in the sealing surfaces.
................................................................
Hello,
For sealing old surface mating the O�ring�
I used  Loctite  Ultra Grey imported car   silicone its made for
aluminum not sure of the number
And you have  another brand made by  permatex Ultra Grey sensor safe
its a gray tube of 99 grams both are non corrosive for aluminum
Both tube are the same color(gray) different brand made by the same
company Loctite
the  product differ a bit but do the same job
I think loctite is the first one to introduce that stuff

When you try ultra grey silicone you gone forget all the other stuff
bleu red black ect....
http://www.loctite.com/
just my opinion

sorry for my english  should have inserted 50% french language ? <:-)))

Denis Belisle

Quebec canada