loosing water

[Enrique Claure <spanlab@ceibo.entelnet.bo>]

Hi list, me again with water problems. After I changed the radiator cap my 
fans worked correctly when heat built up after normal driving. However, 
when I made it home I noticed the gauge go up and the fans did not operate. 
I looked under the hood and I was loosing water through the expansion tank 
vent tube.
The Haynes manual specifies 15lb cap. I found a 16lb cap but I doubt this 
is the problem. Any ideas? TIA, Enrique