80q coolant flush/refill worry

[Fred Munro]

Hi Megan;

A coolant mix low in antifreeze wouldn't cause the car to overheat. You may
have an airlock in the coolant system.

>From your post, you had about 1.5 litres of water left in your engine. That
means you now have a 29% antifreeze mix for coolant. To get to 50%, drain
2.1 litres out and add 2.1 litres of pure coolant. The calculation is as
follows:

You want 3.5 litres of water in the engine coolant mix.

You now have 5 litres of water and 2 litres of antifreeze (29% mix).

To have 3.5 litres of water, you need 3.5/(1 - 0.29) = 4.9 litres of the 29%
mix.

Drain out 2.1 litres to leave 4.9 litres of mix in the engine, top up with
2.1 litres of pure antifreeze, and you now have 3.5 litres of water and 3.5
litres of antifreeze in the engine - 50/50 mix.

It is good practise to use distilled water rather than tap water to reduce
the potential for scaling - tap water contains calcium and magnesium (as
well as chlorine, chlorinated organics, PCB, antibiotics, various female
hormone mimics, etc., etc.)

Fred Munro
'94 S4



-----Original Message-----
From: quattro-bounces at audifans.com
[mailto:quattro-bounces at audifans.com]On Behalf Of Megan Bigelow
Sent: September 1, 2004 8:08 PM
To: quattro at audifans.com
Subject: 80q coolant flush/refill worry


So I decided to flush and fill the coolant tonight on the ole 80q. I
drained/flushed it without incident, and then here's where I went
wrong. The bentley and the Audi coolant bottle called for a 50/50 mix,
and bentley said the cooling system's capacity for that was 3.5L of
each water and coolant. Not realizing that there is still water from
the flush stuck in parts of the system, I measured out 3.5L of water,
added it, and then tried to (unsucccessfully) add the approx. 3.5L of
unmixed coolant that was in the new bottle of Audi coolant.

Oops. There was 1.5L of straight coolant still left in the bottle.
D'oh! And, upon letting the car idle until the fan kicks on, the
coolant light flashes, and it's definitely not low. So I think it is
overheating.

I guess this is more of an "I'm stupid" post than a question, but I
just wanted to run it by the list's collective knowledge that what I
need to do is drain and refill properly before draining and flushing
the whole system again and buying more coolant at the dealership
tomorrow.

Curses,

Megan

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