I failed to heed the rule "if it aint broke, dont fix it". After reading posts about how the old gray cap needs to be replaced with a new green one, I did that when I did my 90K service. Within the next day or so the coolant warning light came one. So I topped it up and tightened the new cap harder. Now the light occasionally comes on, usually accelerating uphill. Should I put the old cap back on? The new one seems to be harder to thread and I was initially afraid to crank down hard since it felt like it might be different thread pitch. I now have it cranked down to the max.