[BirdDog]

Ok, not 100% sure I get what you are asking, but I'll try...

You need to check the coolant when the car is cold (don't open the cap when it's hot!)

If you fill it up to the Max line, it should not overflow when hot. It's normal for the coolant to rise in the overflow tank when hot, but again, it shouldn't overflow.

The pressure relief valve (are you talking about the valve on top of the tank under the plastic cover?) should only be open when you are purging air from the system. Once the air is out of the system, you should close the valve (by laying it down flat).

Air in the system could cause the coolant to explode out of the top of the coolant overflow tank (via the cap) and it will drain to the ground in front of the right rear tire.

If the coolant tank itself is leaking due to a crack it will leak coolant into your trunk (lift carpet to check the base of the tank). If it leaks through the relief valve, it should follow the same path as if it was coming out of the cap (ie, end up in front of right rear tire).

Have you checked that your radiator fans are working? If the car overheats (or even if it runs a bit hot) it could cause some coolant to be thrown out via the overflow cap. Keep in mind that the dashboard gauge is notoriously inaccurate on these cars. Do you hear the fans come on, and do both come on? You cleaned the radiators - did you do it by removing the front bumper cover and cleaning out between the radiators and the A/C evaporators? Just vacuuming through the front intakes usually won't get it all out.

Ok, that's all I've got!