What would cause the radiator to fill up the overflow tank when it gets warm not hot.

When i put the fluid in i left the line to the thermoste off untill fluid was comming out then filled the radiator up. So you think i might still have air in it. I have sucked a lot of fluid out of the overfill tank twice it completly filled the tank up.

the fluid has to get past your radiator cap to get into the surge tank. if your cap is bad and doesn't hold pressure, fluid will go straight in the surge tank. maybe your cap isn't all the way on tight. there are usually two levels of "tightness" on radiator caps.

Well its not boiling has not run long enough for that. So i will look into the air tomorrow. Thanks Chuck.

make sure the line from radiator is on the nipple above the cap seal and not on the one below the seal. and cap off lower nipple.

It holds pressure.

are you referring to the rad. cap holding pressure?
so, when you start the buggy with the cap on tight how long before you start getting fluid pouring in the overflow tank?
before you start the buggy, pull the overflow hose off the tank. let me know how long it takes for the fluid to start running out of that hose. it should not come out at all unless the buggy is running hot. that cap should hold the pressure back. if it's coming out before it's even hot then your cap is shot.
can you take your fingers and push in on the spring inside the cap? does it spring back or is it depressed or loose?