What is the best coolant to use in my T3. I went to the local vw agent and he said you can't buy G11 any more.

where are you located you probably carn't buy from VW dealer but after market shop will have it

G12 or G12+ are fine I'm led to believe so is what I use.

nulon make the blue euro coolant

Thanks for the replays
im in camden south west sydney
G12 and nylon blue both look like they will do the job

Phosphate free is what you want. most people say to go with the vw approved stuff though

OK G11 coolant is still available you can get it from Stoakers or justkampers are only 2 of the suppliers, I have been advised to avoid the 12 and use 12+ incase there is a mix up and are temped to use or accidently use the wrong one. The three coolants are not inter mixable and if you change from one to another coolant there may be some problems.

Now the big hype about coolant is to preserve head studs and avoid corrosion of the heads. Well the corrision of the heads was caused by a gasket sealant VW used on the heads it caused electrolysis of the heads and subsubquent leaking. This was changed after 1989 some time.

The Head studs 1989 and before didn't have a protective coating to protect them this came into play in 1990 and any engine rebuilt since then has been put together with the head studs with the protective black coating coolant is still wise.

I blew a hose in the 2001'2002 and it was Sunday I was on a trip I purchased a coolant that protected the alloy and other metals from corrosion it was green could have beem repco or supacheap I was desperate and i used it for about 10 years without changing it its now 2017 and my engine is still running strong without problems.

https://www.youtube.com/watch?v=_de0GRWRtuY 
https://www.youtube.com/watch?v=DgwcSOSW4JE 
https://mechanics.stackexchange.com/questions/33100/mixing-coolants 

Which ever coolant you choose , ensure the entire system is sound and maintained. If you change from one type to another, flush it a few times with distilled water first. Keep in mind there will be a few litres (~5L) left in the system after you drain it, this will affect your concentration when refilling.
The system holds ~16L, depending on how you drain it you will get ~11L out. It's good to keep an eye on the header tank, any debris in the system will collect there, so it a good indication on the systems health.
If you still have all the original plastic and steel pipes it's worth keeping an eye on them as they are getting old by now. The steel pipes will corrode under the hoses, the plastic will split under the hoses.