Failing expansion tank cap?

[alpac]

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?

[alpac]

Bump!

[fast4d]

the expansion tank is known for cracking. mine had a very small hairline crack. right under the hose connector. I replaced the hose but soon figured out it was the tank.

[alpac]

I replaced the expansion tank cap yesterday. I drove the car on the highway for 1h30 yesterday night. Drove in town today, rev the engine from time to time. No more leak and no more problem. I may have found the issue here. The funny thing is that 18months ago I had a similar problem. First the small hose connected to the top of expansion tank broke. The garage replaced the hose without looking at any possible underlying cause. The following day a bigger hose got disconnected from the pipe due to too much pressure. I had to get the car towed to the garage. They checked for possible head gasket problem. Compression tests were done with negative results. The garage then decided to replace most components of the cooling system (Radiator, Water pump, Thermostat, etc...) all under the extended warranty (Pfeeew!). Did not have anymore problem until 3 days ago. Now I am wondering if my problem from last year was not just due to a bad cap. Last year they did not change the expansion tank so they probably did not change the cap either.