4355 mf tractor?

i have a 4355 mf tractor that had a bird nest in it and caught on fire i had to replace thermostat and temp sender and a few other things after i had it fixed tractor started running poorly so i took it to one of my neighbors took injector pump off sent it to diesel injection for repairs pump had metal shavings in it put pump back on and water pump started leaking i have since put on three new water pumps and all of them leak after about 5 hrs,could this problem be caused by an idler gear failure or the fire or could it be something else i need to be looking for any help would be greatly appreciated