[Biturbos4] Strange loss of coolant

[Chris Semple]

My bet would be on the aux electric waterpump under the intake manifold. Common cause on hard to find leaks on the 2.7T cars.

 -Cheers
-Chris Semple
Concord NH
'04 S4 std
    '07 S6 v10
        '08 E350 Club

-----Original Message-----
From: quattro [mailto:quattro-bounces at audifans.com] On Behalf Of Mark Rosenkrantz
Sent: Thursday, June 30, 2016 1:36 PM
To: Ti Kan
Cc: Bi-Turbo Audi S4 Audi Fan Group; Audi List
Subject: Re: [Biturbos4] Strange loss of coolant

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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