i have a 1990, 300m with a very slight leak somewhere from the cooling system evidenced by a slow dripping of antifreeze from the botton of the radiator. i have pressure tested it and found no drop in pressure. when i run the motor with the pressure guage attatched the pressure rises very steadily - no spurts or jumps, and gets up to the "danger" mark on my pressure guage. it has a 16 psi cap. what is the operating pressure for the cooling system supposed to be? any ideas. ps. it was 90 degrees when i tested it. thanks. brian