<VV> DIsappearing Water Question - No Corvair, obiouvsly

[RoboMan91324 at aol.com]

Grant,
 
It may be that the overflow from the radiator to the overflow  tank may be 
greater than the capacity of the tank.  It overflows and loses  fluid to the 
street and then sucks the tank almost dry when everything  cools.  Here are 
a couple of points.
 
Lack of overflow staining may not be enough evidence that it  isn't 
happening while driving. I assume that there is a tube that leads from the  tank to 
the bottom of the engine compartment to the street. Place a tin can some  
place in the engine compartment and run the overflow tube to it. If it has 
fluid  in it after a long drive, the radiator is overflowing more fluid than 
the tank  can hold. 
 
Check the tank immediately after a drive that is long  enough to heat 
everything to the max.  If the tank is over-full, then you  are losing fluid for 
that reason.  Your radiator cap  may be the wrong pressure or may have lost 
its pressure capability over the  years.  If it is weak, it will allow more 
fluid to escape  to the  tank.  Lower pressure will allow water to turn to 
steam at a lower temp and  force more fluid into the overflow tank.  Check 
the cap gasket for cracks  and the seat for crap.  Even if there is no visible 
problem, the cap could  still be bad.  A new cap (a good one) is a lot 
cheaper than  constantly replacing antifreeze/coolant or destroying  an aluminum 
head due to undetected overheating.  If the new cap doesn't  solve the 
problem, you can sell it on eBay as a Corvair radiator cap.   lol  You need 
proper pressure and a good seal.
 
Don't refill the overflow tank each time you drive.  See  if the radiator 
fluid level goes down after several driving sessions.  If  it remains full, 
the fluid isn't leaking directly into the engine or out of the  engine other 
than the overflow system.
 
Your thermostat may be getting wonky.  The water temp may  be getting 
higher than when the car was new but maybe not high enough for your  temp light 
to flash on.  Temp sensors/gages and snap switches can be  fairly inaccurate. 
 Higher temp means higher pressure  and more overflow.
 
If your engine is running well, it is unlikely that you have a  head gasket 
permitting combustion gasses into the water jacket but it is worth  
mentioning.
 
Good luck,
 
Doc
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
In a message dated 8/8/2015 7:14:44 P.M. Pacific Daylight Time,  
virtualvairs-request at corvair.org writes:

Message:  3
Date: Sat, 8 Aug 2015 18:12:03 -0400 (GMT-04:00)
From: Grant Young  <gyoungwolf at earthlink.net>
To: "virtualvairs at corvair.org"  <virtualvairs at corvair.org>
Subject: <VV> DIsappearing Water  Question - No Corvair, obiouvsly
Message-ID:
<32646490.1439071923549.JavaMail.root at wamui-mosaic.atl.sa.earthlink.net>

Content-Type: text/plain; charset=UTF-8

Having had no luck  with the PT Cruiser Forum, I am hoping to find some 
experience or knowledge on  a water cooled mystery I have with my wife's '05 PT 
Cruiser GT. I noticed that  every time I checked it out that the coolant 
overflow tank was below the low  level line. I would top it up to the full 
when cold line, but would find the  same problem the next time I checked, often 
the very next day. I have not ever  had to add water to the radiator as it 
is always visible when the radiator cap  is removed. I had the radiator out 
a few years ago to replace the A/C system,  but bled it properly and there 
has never been an overheating problem. I  removed the overflow tank today to 
confirm it did not have a leak. It is a  simple system with a single hose 
from the radiator fill neck to the overflow  tank. The tank has a vent near 
the top. There is no staining anywhere that  gives a clue about the water 
leaving the overflow tank. I quit adding  antifreeze and simply top it up with 
water now due to 
the cost. While it  has not caused a problem, I am not one to simply leave 
well enough alone when  it doesn't do like it should. It has not always been 
this way, just during the  last year. Any ideas? No I can't get rid of it 
because it only has 84K and the  wife likes it too much and wouldn't know 
about the issue otherwise and doesn't  like to drive my Jag. Thanks for any  
thoughts.
Grant