Well, I dug into both engines this weekend and came across something interesting. One engine had the pressure valve plunger installed backwards... actually jammed in the grommet. This generates a few questions for me:<br /> - What symptom would this cause? This engine ran "normal" for temp, ie .. no alarms.<br /> - How does the pressure valve operate? <br /> - Should I expect any engine damage from this?<br />At the same time I checked both thermostats for correct opening temp and gap. Both looked OK.