My 2010 A3 2.0tdi (140) sits at a coolant temp of 70 degrees and only gets up to 90 when stuck in traffic or parked up. Is this a side effect of the emissions fix or is something mechanical wrong?
Yeap if you're confident coolant sender's are working ok, diagnostics should help, them as Lee advises, thermostat would be a good thing to check, change.