[M.D. Holloway]

Chances are, the plastic is a thermo-set material which means once it has been processed and cured you can't melt it back. Plastics are catogorized into two families - Thermoplastics (which can be remelted and molded) and Thermosets (which can not be re-processed or remelted without draqstically changing the physical properties).

For high temp, automotive applications, thermosets are typically used. Not sure you will want to try a repair job to get you through.