2001 A6 4.2 typical coolant and oil temp?
 

Just picked up a new A6 since my last one was totaled. This is a 2001 A6 4.2. My question is what the typical warm-up should be on this motor?

The coolant temp indicator seems to fluctuate a bit. It will warm up to a directly vertical position only at a stand still or in slow traffic. If I am on the highway it will cool a notch or two and then return to vertical a while after sitting.

The oil temp never seems to get very high either. A notch or two above the 150 mark.

My last car was a 2.8 and the coolant would warm to vertical and stay there.

Any thoughts on this? Bad coolant temp sensor?

The oil temp sensor is in the oil pan on the bottom of the engine. I've replaced mine when oil temp was at cold but engine was hot. Use only the Hella brand name sensor. Others won't work.

Your coolant temp issue may be a sticking or recalcitrant thermostat. Replace it when the TB and waterpump are replaced. Watch it for now.

This could also indicate a very low temp thermostat was installed, or no thermostat is installed, or it has been disabled.

Radiator fan is controlling temp while sitting, but when you drive at higher speeds, ambient air is cooling down coolant to a lower-than-normal operating temp.

Agree with doing a new thermostat (87 C) when you do the TB service.

Thanks guys. It' going in tomorrow to get the timing belt done and I'm going to have him swap out the thermostat at the same time.

Many people change the waterpump at the same time as the TB. As well as the tensioner and pulleys.
Shame to have them fail and take out the engine.