Answers can be found in TM 9-803, page 70 and 71.

You should know what your jeep’s safe operating temperature is.

Engine Warm-up.
Temperature Gage. Engine temperature should rise gradually during warm-up period to normal operating range, 160F to 185F.

Run-in Test.
Dash Instruments and Gages. Do not move vehicle until engine temperature reaches 135F. Maximum safe operating temperature is 200F.

You can also see info under the “Road Test” and “During Operation” section.

Basically, if your are not losing coolant either from the block or the radiator then don’t be overly concerned about the engine’s temperature.  Some of it has to do with whether or not you are running a 165F or 180F thermostat.  Ambient temperature and engine load (how hard the engine is working) all have impact on the temperature.  Later models of MB/GPW were equipped with the 180F thermostat as the higher temperature helps to cook off contaminants in the oil supply.

You can find this out and more in TM 9-803 Willys Overland Model MB and Ford Model GPW ¼ Ton 4×4 Technical Manual.  If you don’t have one and own a WW2 jeep then click the link and order your copy today.

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