coolant leak no visible signs
 

i have a 93 z28 that is losing coolant even with the engine not running
you can fill the radiator and come back about an hour later and it's empty
i know it can't be the heater core cause all hvac components have been stripped
there are no puddles on the gorund either

pressure test it

but, please clarify something

Engine off and cool
you fill the radiator completely
you do not run the engine
you walk away a few hours, come back and it's down a lot again?

it's important to be precise with descriptions

Is it coming put plastic overflow?

One thing we know for sure its going somewhere. Just keep filling it up :)

^ Right, something should show as full sooner or later....either the radiator or crankcase.
Just don't have the car parked on a hill, sure would hate for it to float away! ;)

engine off and cool
fill radiator
do not run engine
come back few hours later and it's empty
and i'm sure it's not the recovery tank

however i was told that it could be back flowing through the oil cooler and going straight into the oil pan

Check the dip stick for water. It should be showing over filled as the oil will float on the water. If there is any chance there has been coolant in your oil DO NOT start the car. You will wipe out every bearing in the motor.

if it is backflowing through oil cooler
what do i need to do to fix it

I'd just bypass the oil cooler. All you need is some caps from the auto parts store that'll go on the water pump and the drivers side bottom radiator.

Then next time you change your oil filter (which should be right now if you have coolant in your oil), you can remove the cooler piece and install a filter directly on the block. What I don't remember is if you need an adapter or a different oil filter. I haven't done that yet, but I did do the oil cooler bypass caps on my '94 LT1 earlier this year with no trouble, and I live in the desert.

what kind of caps are you talking about and where can i get them