[s-cars] Still losing Coolant (after a new headgasket)???????

[CyberPoet]

1. The fact that your head gasket failed indicates that your pressure
blow-off valve in your coolant recovery / reservoir tank is not working
correctly. Replace it ASAP for piece of mind. They tend to go bad with
time, and if you are poor, soaking them overnight in vinegar and then
brushing with a good toothbrush may help (but no promises). The same
cap is used for everything from a mid-80's VW Golf through current
Audi's, so don't let your Audi dealer fleece you on the price.

2. I am guessing that you have already replaced every hose in the
cooling system, including the hoses to the dash, the reservoir tank and
the various water pump/block/radiator hoses. If you have not, do so
now. While you are at it, replace every hose clamp in the system with
American-style threaded-nut hose clamps (rather than the snap-on and
clamp-down hose clamps used by Audi); the stock clamp designs can fail
sporadically and permit small amounts of coolant to escape. Make sure
you replace the ones for the overflow tank as well.

3. Loss of coolant can occur via any passage the coolant passes
through. Based on your symptoms, I'd hazard a guess that you are losing
minor amounts of coolant through the heater core (verses to the head
gasket, radiator) or at a hose/hose-clamp junction, and that when the
system dropped below a certain level, the steam pressure in the block
as a result because high enough to cause the head gasket failure.

4. Finally, insure that you never, ever, ever overfill your reservoir
tank even a minor amount. This is enough of a pressure difference in
the system at operating temperatures to force a leak somewhere under
normal conditions (unless that overflow valve in the reservoir cap is
working perfectly). If I ever find a suitable secondary overflow valve
that I can place into the hose system, I will let everyone know ASAP,
because the stock cap seemingly goes bad every 5 to 8 years... Until
then, head's up.

Best Wishes,
=-= Marc Glasgow

Dave wrote....

> I have a 95.5 S6 Avant which was slowly losing coolant without a
> trace( i.e.
> No puddles on the floor or dripping in the engine compartment).  This
> happened for a month or so and had my local quattro specialist
> stumped.  One
> morning I checked the Oil and it looked like chocolate milk.  Mechanic
> (#1)
> "must be the Head Gasket although, I have never seen one go bad!!"
> They
> were 3 weeks out and referred me to another Mechanic (which I hate
> doing)
> and they completed the job at twice the quoted price after 5 long days.
> Needless to say I got the car back and was still losing coolant after
> waiting for the "air pocket" to work its way out.
> I brought it back and they (mechanic #2) did a pressure test (found
> nothing)
> topped it off and sent me on my way.
> I AM STILL LOSING COOLANT????  I have a feeling it was miss diaganosed
> and I
> payed $1,700 + for a new Head Gasket I did not need.  Has anyone had
> this
> problem?  Could it be something internally with the Turbo they did not
> check.  I need some ideas as I need to have them make things right.