Does A Bad Thermostat HAVE To Be Fixed To Drive

I have a 1996 Ford Escort LX Wagon. It is an automatic and it has 120k miles. The temp gauge reads cold and the check engine light stays on. When I turn on the heat, I hear a rattling sound. Is this the thermostat? Could I just be low on coolant?

Main question – Would a bad thermostat absolutely HAVE to be fixed to drive?

Answers for The Question

  1. Vipassana
  2. Hyway