I don't think 210 is that bad. If the system is properly pressurized, you shouldn't boil over until you go over the 220-230 range. It also depends on the ambient temperature. If the condition you are describing is on a hot day, then it is completely normal. If it is reaching 210 on a cool day (<70F), then you may have an issue. Rule of thumb is, no boilover, no problem.