1994 Toyota 4Runner over heating and white smoke

You've probably already figured this out but if not it sounds like a head gasket problem. This particular model had a bad head design.

I'm not a professional mechanic but I have done my own head gasket repair and this sounds just like what I went through a couple years ago.

One thing you can do it pull each spark plug out and inspect the tip. If it is shiny or wet looking you've probably got a head gasket failure. There are other things you can do like a compression check as well. Does the white smoke have a sweet smell?

Try these checks and avoid starting it if you can.