my engine has been rebiult a month ago. when the car gets hot the expantion tank overfills and leaks from the bottom.my mechanic said it was the a.s.tanks cap so he changed it he said it was letting coolant go to the expantion tank too soon.my problem is that the cap he put is a 1.1 bar but the original pressure cap was a 0.9bar. some people told me that the extra preasure will damage my radiator or even the o-rings.please does anyone of you guys now anything about this?

 

i could be wrong, but i thought originally, mazda used a 1.1 cap, but later changed to a .9 cap for reasons similar to what you said