Yesterday after driving on the highway for about 1h and stopping to get some gas I noticed a little bit of steam from the engine compartment. I checked it out and found that the steam was coming from one of the small cooling hoses. The hose is not cracked and looks good. Actually this hose like all others were replaced 18months ago as well as the radiator and water pump. The leak came from the connection between the hose and the pipe. It looked to me that the entire cooling system was under too much pressure. I very carefully opened the expansion tank cap to release the pressure and resumed my trip for another 30mns. There was no more steam nor obvious leak. The car never overheated and the oil looks very good so I ruled out a head gasket or thermostat issue. I am thinking of a problem with the expansion cap not releasing the pressure properly and I am planning to replace the cap.
For the techies of this board, what do you guys think?