It goes back WAY longer than 1990 - something the old timers usually recommend. You just dump black pepper in the radiator/coolant reservoir and let it circulate. It apparently finds its way to any holes and clogs them up. It sounds safer than the products on the parts store shelf, since it should be easy to flush out. I scoffed, but I honestly believe it would have solved my problem (temporarily) when my heater core had a pinhole leak.