Or just get the uv light kit. $20 or so. you put the die in the coolent and use the uv light to find out where it is leaking.

 

I was having a similar issue. But I found where mine was leaking. Turns out that the hose that I bought at autozone had one of those plastic loops through it so that they could hang it up. I asked if that hole was too close to the middle. And parts guy said no but obviously it is. And you can see where it hasbeen leaking out of the upper hose, onto the radiator neck and onto the little lip on the top part of the tank. I willcurt an inch or so off of the radiator end and reconnectit to see if that doesnt take that hole out of the pressure part of the hose.

 

Yeah I have been having the same problem with my 94. I put a new rad into the truck in sept. 07 and after that have been losing my resovior in about week and a half 2 weeks. Had it pressure tested at my buddies performance shop had them look at it and no leaks????? Cant figure out where it goin but my head is good and intake is fine as well. No problems with anything just dissapearing coolent???