[Biturbos4] Strange loss of coolant

[Mark Rosenkrantz]

Also, look around the turbos, etc.  G12 leaks leave a white, almost
powdery residue behind as evidence.

On Thu, Jun 30, 2016 at 4:22 AM, Ti Kan <ti at amb.org> wrote:
> Hi folks,
>
> My 2001.5 S4 did something weird that I cannot explain, maybe
> someone out there would have an idea what happened.
>
> A few days ago I drove home as usual, the car ran fine without
> any signs of trouble.  It was a very hot day so I had my A/C
> running.  Upon arrival, I parked it outside, and noticed a small
> trail of water behind the car.  It didn't concern me at the
> time, thinking that it was just condensation from the A/C.
>
> About 3 hours later I leave to go run an errand.  As soon as
> I started the car, the auto-check system displayed the big
> "low coolant" warning symbol.  I shut off the car to check
> under the hood.  Sure enough, the coolant reservoir was dry.
> I had checked the level recently, so this is not due to a
> slow leak.  However, looking around underhood, I cannot see
> an obvious place where the leak might be.  The first thing
> that comes to mind was hoses, the expansion tank, or the
> expansion tank cap.  There was no sign of coolant or wetness
> anywhere that I could see, except on a small hose that runs
> from the fuel pressure regulator to the intake manifold.  The
> hose looks like a vacuum hose to me, it has a woven cloth
> exterior, but it was wet.  I don't think the hose itself was
> the culprit, but perhaps the coolant leaked from something
> and got this hose wet.
>
> I also examined the radiator area, the heater hoses, the
> plenum area where the heater hoses go to the heater core.
> I also checked the interior floor carpet... all dry.  There
> was no musty smell in the cabin.
>
> Hmm.  OK, so I refilled the expansion tank back to the proper
> level with distilled water and G12 coolant mix.  The total
> amount I had to pour in was a little over 1/3 gallon water
> and the same amount of G12, making it 2/3 gallons total.
> The cooling system capacity was not listed in the owners manual,
> so I searched for it on the net, and found it to be 1.58 gallon.
> This means that the system lost 2/3 gallons, but still had about
> 0.9 gallons in it.
>
> That's enough coolant loss, more than what would only get a
> small hose wet.  I dried that hsoe with a paper towel just to
> see if it gets wet again.
>
> I drove the car for 2 days now, and the coolant level
> is staying pretty much where I filled it.  I don't see any
> signs of leak, no puddle under the car, no trail of water behind
> the car.  It seems as if the problem cured itself.  That small
> hose feels a little damp.  I'm not sure if it's new leak
> or it's still coolant from before.  The cloth texture of
> the hose seem to retain some water even after I wiped it.
>
> I am still baffled about this, and carry distilled water and
> G12 in the trunk just in case, but what could cause an apparent
> big loss of coolant and then act as if it never happened?
>
> Sorry about the long post.
>
> -Ti
> --
> 2003 A4 1.8T
> 2001.5 S4 2.7T
> 1984 5000S turbo
> 1980 4000 2.0
>
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