How to Tell if Your Thermostat is Failing?
Monitor your engine temperature gauge in the morning for telltale signs.
Just how long is it taking for the engine to get up to operating temperature. If it is taking more than 5 minutes the problem could be a weak or failing thermostat. Easy DIY to replace yourself.
Problem & Solution
Common among these chassis:
W110 W111 W112 Sedan
W111 W112 Coupe