Engine Oil Cooler Thermostat: Testing and Inspection

Thermostat - oil filter

NOTE: The following engines are provided with a thermostat in oil filter:
- Engine 615 in model 123.1 on vehicles with air conditioning system.
- Engine 616 in model 123.1 generally up to August 1976 and starting August 1978 on vehicles with air conditioning system only.
- Engine 617 in model 115.1 and 123.1 generally.


Checking
1 Exchange oil dipstick for flexible heat sensor.
2 Run engine at increased speed and watch telethermometer.
3 At 95 or 110 ± 4 °C, a marked increase of oil temperature should be felt (by hand) at oil cooler.

If not, replace thermostat.