There is certainly no harm using distilled water and if you live in a hard water area (one in which the kettle element furs up) then it is a good idea, though I would rather add a 50/50 coolant / tap water mix than run low on coolant. If you live in a natural soft water area then it is less significant. You can get distilled / deionised water from any Halfords (they are not the same thing but no *practical* difference between the two for this purpose)
Are you changing the coolant altogether or just topping up? I have no idea what's in mine except that it's whatever Hartech put in when they changed the coolant and did the head rebuild, changed the water pump and did other good works. I can, however, reliable inform you that it's pink. Folklore says not to mix different colours, but I have no evidence on that one way or another.
The only "recommended" coolant brand is probably whatever your nearest Official Porsche Centre will sell you in a bottle with a Porsche logo on it. On my BMW I use the factory coolant, and that's a blue colour. I imagine I could have bought some similar product a few quid cheaper but given that I only ever have to put in tiny amounts, it's not worth shopping around for. For my Porsche, I've never had to put a drop in, but if I ever needed a top-up I would call either Hartech or Promax to ask what they buy themselves. I've never used EMC, but they also have a strong reputation for the front-engined liquid-cooled cars, so 'm sure they would advise you too.
As for the refilling and bleeding of the system: it is something that requires a bit of effort and technique to get rid of air pockets and bubbles. See here:
http://www.clarks-garage.com/shop-manual/cool-02.htm
]I know I should use phospate free anti-freeze but which brand is recommended and should it be mixed with distiled water. And any tips on re-charging the cooling system. Thanks.
