[s-cars] Mystery coolant leak...

CyberPoet thecyberpoet at cyberpoet.net
Tue Jul 1 06:59:59 EDT 2003

If there is no leakage at the expansion tank, the connection to it, or
the hose, the only coolant-leak culprit left in that area is the
ventilation cap on the expansion tank itself. For most people, the
pressure release mechanism in the cap goes bad over time, not releasing
at the proper pressure (24 - 27 psi ??), but it sounds like your is
releasing early (or you are over-filling the coolant tank). Check it...
it's the cheapest piece in the system :)

Based on your explanation, it sounds as if the system is cooking off
somewhere else (like at the head), generating steam after you shut
down, and the excess pressure is forcing the coolant in the expansion
tank to blow out of the safety valve at in the expansion tank cap. Easy
way to diagnoise: drive till hot, grab a beer, pop the hot and kill the
engine, then wait and watch -- if it's the cause, it should spurt
within a few minutes (definitely within 10 minutes in all cases). If
your system is designed to use a fan that can run after the engine
shuts down (depends on the model -- it's not universal to all audi's),
then it may not be kicking on when it should and would explain

=-= Marc Glasgow
Serving Macintosh Users in Florida since 1990


Has anyone experienced a leak somewhere under the expansion tank (It's
the tank or adjoined hoses)?  It seems to be coming from near the
little black
ABS box.  It doesn't really leak when the car is running, but when I
get out of
the car and return there is about a 1/2 pint of coolant next to the
driver-side wheel.  I lifted the car and tried to recreate, but of
course to no
avail.  Go figure.  Any input/suggestions appreciated.

More information about the S-car-list mailing list