OM 617 – Checking thermostat in oil filter

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 1978 and starting August 1978 on vehicles with air conditioning system only.
Engine 617 in model 115.1 and 123.1 generally.


1. Exchange oil dipstick for flexible heat sensor
2. Run engine at increased speed and watch telethermometer.
3. At 95 +- 4c, a clear rise of oil temperature on oil cooler should be noticed (manually).
If not, replace thermostat.


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