Coolant Temp
 

Coolant temp is not moving from 40* on the dash. If i ground out the sender wire, the dash gauges pegs to "full hot." I assume this is expected behavior and i simply have a bad sending unit?

Thanks!
Alex

What are you working on? It is always at 40 when the wire is connected or it never goes above 40?

300TD. Needle hovers around 40* while driving (outside temp around 10c.

Although, I did a bit more investigation with an infrared thermometer and head temperatures are staying around 45-50c, so I am thinking I may actually have a stuck open thermostat. Plan to remove the temp sender and stick it in a cup of hot water to isolate the issue.

If it reads colder temps and only goes up to 40 the thermostat is bad...been there several times. The sending units have a rather low failure rate and thermostats have a higher failure rate.

I replaced my sender unit and it did the trick. The old one was rusted up pretty badly. I guess it’s only brass plated, not solid brass, perhaps it’s some kind of bi-metal.

Mine also pegged full hot when I did the ground test.