Only one thing blows up filters and that is excessive pressure. Not having enough information to find the schematic for your system you will either have an inline pressure bypass valve or an internal bypass in the pump. One or the other is allowing the pressure to grow until the filter blows. It could be that someone has mickey moused the system to increase pressures because of a faulty fan drive or other issue with this portion of the cooling system. The stacked filters in the reservoir may be partially clogged restricting the intake to the pump and this was "corrected" by playing with the bypass, if it is external. Pull the pump, have it checked but be sure to tell them it occurs after an extended run. Otherwise they will run it for a few minutes and possibly pronounce it good to go. If it checks out ok start looking for wires disconnected, spliced together or other obvious signs that someone did not want to spend the money to fix a previous issue in a proper manner because of cost. This could easily be something as simple as a return line restrictor, normally installed near the reservoir for noise reduction or splash control, that has become partially blocked with age. Good luck with the repair. I hope you can do this yourself because it will get very expensive to have someone else do it.
Randy
