Christoph,
Thanks for your points.
I think it would be difficult to get an UV light here. (have to check)
As for the cap + valve I am not sure I can produce this small tools.
(BTW - Audi uses exactly the same technique)
Best Regards, Jorge

Christoph Bollig > wrote in message >. ..
> > A4 2.8 1996 - 46,000Km
> >
> > Coolant is slowly decreasing. About 1 month from max to min.
> > No leaks, smokes or smells.
> > Temperature - oil & coolant - Ok.
> >
> > Curiously, when I topped the coolant to Max I noticed a few hours
> > later some coolant in the floor. (engine cold - not turned on in any
> > moment)
> >
> > Can it be just a minimum fracture in the higher part of the reservoir
> > or should I be looking at somethng else?
> > I imagine that the coolant works under pressure - cannot understand
> > leaking with the engine cold and no pressure at all.
> > BTW: after the mentioned leak - no more than 12 hours later - no leaks
> > at all. (and reservoir at MAX level)
> > Thanks in advance for your help.
> > Jorge
>
> I think you could use a UV lamp to detect small traces of coolant. On
> alt.lasers, they had a discussion some time ago about using UV LEDs
> for that purpose. Apperently, it works quite well and the UV LED
> shouldn't be expensive. You might have to clean your engine first,
> since they said those thing detect extremely small quantities.
>
> I also saw somewhere mentioned that you could fit a tyre valve (e.g.
> from a bycicle tube) to the cap of the reservoir (best get a spare cap
> for this) and then pump it up to some pressure to detect leaks.
>
> Good luck,
>
> Christoph