Operating the Mog

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2 Operating the Mog

This section is based on Chapter 4 Operating Instructions, of the UHB-Unimog-Cargo.pdf Technical Manual User Handbook published online by AFM Safety (UHB-Unimog-Cargo.pdf).

If you are new to Mogs, then I suggest you download the User Handbook to suit your model, and the various Servicing Instructions etc. that are supplied by AFM. The AFM web page also contains a range of support material. There is a formal U1700L Workshop Manual available, but I think it costs about $600. Mog Central Service Manual

2.1 Check engine oil

The Unimogs are famous for using oil, and for blowing smoke when they first start. You really need to check the engine oil every time you go out - and after a reasonably long period of driving (4+ hours). The oil is the classic heavy diesel 15W-40 oil.

2.2 Start procedure

Start the engine as follows :

Select neutral on the main transmission.
Select two-wheel drive on the drive selector switch.
Ensure the parking brake is applied.
Position the hand throttle in the engine idle detent.
Do not operate the starter motor for more than 15 seconds. If the engine does not start in this time, allow 30 seconds for the starter motor to cool and the battery to recover. If the engine fails to start at the third attempt, abandon the start procedure and report the fault.
Turn the key to the on position.
Ensure the alarm sounds and the low oil, low coolant and high temperature lights illuminate.
Turn the key to the start position.
NOTE Release the key as soon as the engine starts.
Ensure the alarm mutes and the low oil, low coolant and high temperature lights extinguish.
When the engine is running, allow the air pressure to build up to a minimum of 12 bar (7 bar in an emergency).
Check that only the parking brake, differential pressure and the brake pad wear warning lights are illuminated.

Note: the Unimog cant be moved until the two air pressure gauges have reached 8 bar. In mine, this takes about 20 seconds if the Unimog has not been running recently. Once the pressure has reached 8 bar, it continues to climb to 12 bar, where it releases pressure. The 'woosh' sound it makes when releasing pressure will make a first time driver think that they have broken something. No, it is normal.

2.3 Stopping the Engine

Stop the engine as follows :

Do not stop the engine when the coolant temperature is higher than 90^oC. Keep the engine running at 1200 – 1500 rpm for approximately two minutes to allow the coolant temperature to drop below 90^oC.

Move the hand throttle to the engine shut down position.
Turn the ignition key to the off position. Do not leave the truck in gear.
Select neutral on the main transmission.
Ensure the parking brake is applied.

Note: the Unimogs are classic diesel motors. They do not need ignition / electricity to run. If you switch the ignition key 'off' when the Unimog is running, nothing will happen to the engine. It will keep running. You need to remove the fuel to stop it.

2.4 Fording (river crossing)

Prior to fording, select four-wheel drive. This will ensure the truck transmission and axles are pressurised to prevent the ingress of water. Note, the Unimog is labeled as being limited to 1.2m depth. However, I am not clear on why this limit is imposed, or how easily it can be increased (safely). I have seen YouTube videos of Unimogs going deeper than 1.2m, but of course it is unclear if they were scrapped or repaired after, or prepared before. There are breathers between the cabin and the tray. I have not measured their height. They look higher than 1.2m. The snorkel, like most snorkels, is more meant to limit dust ingress than to breathe in deep water.