After some search, I was able to do it. For future reference, here is how I did it :
-Use a "Transmit CAN" block.
-Set the "EXT" at true.
-Set the "RTR" at false.
-Set the length at 8.
-Create an array of 8 U8 bytes.
-Fill the byte0 with the hydraulic temp (from 0-250, 1°C = 1 step, -40°C offset)
-Fill all the other bytes with 255.
-use the following ID : 0x0CFE6803 (FE68 is the PGN 65128, 03 is the address of my MC050 ECU, 0C is the priority)
Voila!
Done!
I hope this will help people in the future!
Sam