[cooling] low on water, but not thirsty

[amalventano at sc.rr.com (Allyn)]

i've noticed that when shutting down on hot days, the cap vents a little bit 
of coolant as the head transfers its residual heat into the (now) stagnant 
coolant. while this happens, steam voids are forming in the head. this 
causes coolant to be forced into the reservoir, building up pressure, 
ultimately lifting the 15 psi relief. when the reservoid is full, water must 
leave out of the relief. repeating this cycle a few times causes the coolant 
level in the reservoir to get lower until it hits a point where you end up 
with only air in the reservoir collapsing on each shutdown (not enough to 
spill coolant though). i've found the equalibrium to be about 1/4 to 1/2 
full on the bottle.
i've never pressure tested a cap on a reservoir that has done this. what 
color cap is on your rocco? anyone remember the cap-pressure correlation? 
(green/black/blue).
hth
Al

----- Original Message ----- 
From: "Foxx (in a box)" <foxxinabox@wideopenwest.com>
To: "Scirocco list" <Scirocco-l@scirocco.org>
Sent: Monday, September 13, 2004 6:50 PM
Subject: [cooling] low on water, but not thirsty


   noticed that my 8v seems to like to get rid of it's coolant. i can
fill the tank up all the way and it'll usually be down to about 1/4" in
less than two weeks. after that, though, it stays at about 1/4" and i
have no problems cooling, even on warmer days (usually stays below
half). don't suggest cracked bottle because i have swapped that out to
no effect. the car does not blow steam out the pipe (no smoking) nor
does it leave puddles. i cannot seem to locate the source of the missing
water (no, it's not mixing with the oil, either). could a bad reservoir
cap be to blame? i'm thinking also heater core (as steam) but it
defrosts perfectly and i cannot smell antifreeze. ideas? thanx.

-- 
  /\_/\   Foxx (in a box)
< o o >   http://foxx.tripod.com
   \ /
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