Sudden water temperature increase

[gkachuk]

On my 2000 986 S the water temperature gauge, after warming up started, creeping towards overheating. I shut her down waited till the temp had cooled down and wanted to add coolant, but the level was correct. (Does this indicate a stuck thermostat?)This happened again after, and before I had the chance to shut her down there was a loud pouf and a lot of smoke. I pulled over and found that the oil filler cap had come off and a lot of water and some oil had spilled into the trunk. Very messy. The next day I went to pick up the car. I started the car and there was an awful lot of smoke from the tail pipes. This however subsided until there was no more smoke and the engine ran fine. I got the car home and tried starting it the following day. Again initially a lot of smoke only to subside and once again I drove the car which seemed to run well. Is this a an oil separator problem? Should I replace it and the thermostat? Please advise.

[pochejp]

Check the coolant for hydrocarbons with a test kit bought at the auto parts store. You may have a cracked head pressurizing the coolant system and the crankcase. I would start there. Hope its not.