first thing you need to ask about over heating is, how much amount of coolant lost in the radiator? Kung halos naubos agad ang laman in a short span of time, chances are there's a leak in the line, from radiator out to radiator in, mostly will be in the hoses. madaming hoses yan, particularly those small by-pass hoses. pag matagal mag overheat or gradual ang increase in temp, small leak in the radiator system.

now kung hindi naman nabawasan yung coolant & ur temp is shooting up, the fans are not working so either fuse, the fan itself or thermoswitch. chekc also radiator condtion baka clogged na ang loob sa dami ng dumi.

now if all of the above is not the problem, then get the timing & tune-up done. still if not, then you can focus at the engine itself.