400 cooling water temperature sensor location

Discussion in '365 GT4 2+2/400/412' started by Martin BB, Jun 21, 2021.

  1. Martin BB

    Martin BB Rookie

    Nov 25, 2020
    Full Name:
    Martin Houwing

    I noticed that the 2 cooling water fans switch off while the cooling water temperature gauge indicates around 95 °C.
    Or the switch at the bottom of the radiator isn't doing it's job correctly or the cooling water temperature gauge is indicating wrong values.
    Question: does a 400 has a separate cooling water temperature sensor and if yes, what is the location? Or is the switch also the sensor?
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  3. Martin BB

    Martin BB Rookie

    Nov 25, 2020
    Full Name:
    Martin Houwing
    Found it! At the back of the right cilinder head. Can these give wrong indications? What is your experience?
  4. raemin

    raemin Formula Junior

    Jan 16, 2007
    Lyon (FR)
    Full Name:
    R. Emin
    You do have a sensor on the radiator. This sensor is calibrated close to the calorstat (~5° appart from memory).

    Based on my experience if the car is standing still, once the engine is hot the fans do kick in and won't stop (unless there is some airflow).

    If the AC is on, one of the fans will be activated regardless of engine temperature. That's a good way to check that the fans fuse and relays are working...
  5. SouthJersey400i

    SouthJersey400i Formula 3

    Mar 14, 2007
    Romulus, NY (Finger Lakes)
    Full Name:
    Ken Battle
    The temp gauge sender is in the Vee of the motor that you found. The fans are controlled by a switch on the bottom / rear of the radiator. The motor outlet will always get up to thermostat temperature but the bottom of the radiator may still be cool if driving at normal speeds. That switch failed on my 400i. They are available from F-sources or generic ones. There is a significant gap between the "on" temp and the "off" temp (maybe on at 90 and off at 80?). I forget the original specs but I changed mine to one that comes on lower and stays on longer.

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