Autozone rents pressure testers for you to test your rad yourself. I really think the problem I have is in the rad. It's winter here now so even though I now have a working datalogger I can't test to see if it was really overheating. I am loosing coolant somewhere though. I can't see any leakes in the hard or soft lines, so I think the rad is the only cause. Does anyone know how to do a pressure test on the rad to see if it has a crack somewhere. It's not losing liquid fast enough to be a real leak. nor does it leave any puddles or stains anywhere.

anybody know how to do this?

well only way I can think of is ..
take the radiator off and have it completely emty.
make some sort of cap for the ends, but leave and opening for a hose off a compressor.
make a solution of soapy water and sparay it on the radiator.
Now pressurise the the radiator and loook for leaks...
hope I explained it somewhat.