Having lost 2 birds within 30 minutes of each other, I can attest that high heat exposure will release teflon vapors and kill birds. My husband had returned home after living in another state for work and brought back his kitchen pots, etc. Unbeknownst to me, one of the pans contained teflon. My son used that pan to cook bacon over very high heat, suddenly killing 2 of my babies. Luckily our other 11 birds survived the exposure.
My thoughts are that if his radiator reached high temperatures, it could have activated the teflon tape. It's quite unusual for such a young bird to quickly die like that, unless he had an undiagnosed medical condition.