[Biturbos4] Strange loss of coolant

[Andrew Lundy]

Sounds like the car got hot to me and the coolant reservoir overflowed.

I don't know the details of your drive that day. But if you sat in traffic
for a while or got stuck at a bunch of stop lights with the high temps, the
temp could have went up in the car and started to overflow.

When this happens it is a sign that one (or both) of your electric cooling
fans is dying. At speed the car will stay cool...but stopped it will warm
up. If the fan is just starting to die it may only happen on hot
days....but it will slowly get worse and happen on cooler days too. This is
pretty common...BTDT.

Another possibility is a bad cap on the reservoir that couldn't hold the
excess pressure on the hot day. This is possible, but not as common on
these cars.

Good luck!
On Jun 30, 2016 3:22 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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