I have 98 F150 4.2L with 90,000 mi. I have had problems with water/coolant disapearing. Pressurized system couldn't find a leak. Motor locked up on me. I called around about getting a new/ rebuilt motor or having this one rebuilt. Someone told me these motors have a lot of problems with water getting into the intake and with the heater core going bad (which I also just replaced). Does anyone have information regarding any of this?