The two hoses from the engine to the heater core plumbing at the firewall came off. The plastic piping the hoses attached to became brittle and weak from engine vibration. I tried threading 1/4" pipe threads then installing pipe nipple to which I attached heater hoses from engine-workked for a while then failed. There is very little room to work with between firewall and the engine. Did anybody else have similiar problem? I'm curious to see how plastic piping goes to heater core.