Have a Mercedes E220 cdi 2001. Temperature will not rise to the required 80 or 90 degrees when driving (stays at just above 40). Hence the interior will not heat up. Replaced the thermo on engine and still the same problem. Can anyone help me?

 

is 104F ,something is wrong,big time.It should not even run.Codes should be present.Either the thermostat was bad and is stuck open,your coolant level is way down,or your coolant temp sensor is bad.Get it to a shop if you can't figure it out quickly.Because you will or are doing potential serious harm to the engine.Now
bleed the air from the coolant and check fluid level,first.