On my 1989 E-350 460ci with the accompanying access limitations I understand there are two separate coolant temperature sensors. I think one is top front near the thermostat and the other is in the rear near the distributor. I could be wrong about these locations and would appreciate a more precise description.

Anyway, my problem is the dash gauge reads very low, hardly moving off cold when operating normally. The thermostat has been replaced so I would like to replace the sensor. My question is where specifically is the gauge sensor located?

 

Locations sound about right, Your looking for a Coolant Temp (Sender) for the Gauge it's small one wire connector. The Coolant Temp (Sensor) will have a larger sealed/locked two prong connector for the computer........

 

The temp sensor with the single wire is the one in the front, just behind the radiator hose gooseneck. That's a good thing being it's far easier to reach that one compared to the one in the middle of the engine that is buried in plumbing.