[Biturbos4] G12 antifreeze

Keman keman at interwolf.net
Wed Nov 16 18:30:24 EST 2005

G12 works good. I wouldn't try anything else. If you want it cheaper, you
can get it at www.ecstuning.com for $9.95/1.5 liters. Dilute 50/50.

If you do choose to drain/flush/fill, keep in mind that the biturbo engine
has no radiator drain. You're unfortunately only left with the block drain
that's accessed via the green 8mm hex bolt that's pointing down between
where the trans meets the engine, through one of the circular holes. It's
about 5" up there right where the clutch is, so you need a long 8mm hex
key, and it will REALLY put up a fight breaking free. It has a green
o-ring that you should replace if you remove that bolt which you can get
from the dealer for cheap.

Now for the hard part. (That wasn't hard enough?)

To refill, you need a vacuum coolant fill tool. This evacuates all air
from the system and holds a vacuum using shop air, and with a turn of a
valve the system sucks coolant from a bucket all in one shot and
completely fills the system. It connects at the coolant surge tank,
screwing in place of where the reservoir cap goes. Failure to do this will
result in tons of air in the system and you might not even be able to get
it all out. You'll have a lot of cooling issues with air pockets that
refuse to be purged. Said tool is $$$ .. rent/borrow one if you can.

I did this about every 50k miles, or when the coolant started darkening
up. I put a new coolant reservoir ($35) on at the same time, which really
freshened the engines appearance up since it's sparkling clearish white
when new and comes with a new cap.

It can be better to sucker an unknowledgable dealership into doing this
for you for cheap-- all other Audi's have a coolant drain in the radiator
and the tech will be expecting that if he's never drained coolant from an
S4 before. Oh will he be surprised.... ask me how I know. ;)

On a more serious note, coolant doesn't generally escape. If you're losing
it, it's probably going somewhere. Luckily wherever it goes, it will leave
a ton of pink crustys. Try to trace the trail from under the car, and
check out in the V of the engine under the intake by looking directly
under the throttle body with a flashlight. There's some O rings on the
black coolant hardline where it enters the engine block which can leak, as
well as the coolant afterrun pump (that wierd looking thing about the size
of a soup can). It can also come out the back where the coolant hardline
makes a T. Occasionally it comes out of the water pump or the oil cooler,
though rarely. Just follow the trail if you find one.

Good luck!

- Keman

On Wed, 16 Nov 2005, mike mcclurg wrote:

> Cooling system was low this morning so I went to my
> friendly, local dealer and bought a gallon of G12.
> $23!!!
> I know you are not supposed to mix regular antifreeze
> with the stuff, that's why I bought it to top up the
> system. But what is the collective wisdom concerning
> draining, flushing and replacing with some more
> reasonable stuff?
> Is there something else we can use that is "just as
> good"?
> Thanks,
> Mike

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