Changing the fan belt
on a Mercedes MBE 900 diesel engine is pretty basic stuff considering all the other possible repairs. The fan belt however is very important considering what it does for the engine and what could happen if it failed. The alternator would quit charging, causing an electrical system shutdown and the engine would eventually overheat causing an even bigger problem! So when you think about how important the fan belt really is it's essential to check it closely during maintenance checks.
The Multi-ribbed belt [8 ribs] has a tensioner that keeps the belt tight. This is a normal design for most modern diesel engines. The only disadvantage is getting at the tensioner with a wrench or socket to relieve tension on the belt enough to remove it. In this case with the Mercedes diesel, I found getting at the tensioner from underneath to the be the easiest method.
Looking down on the fan assembly you'll see a electrical connection and wiring along with a fibre strap that's bolted to the fan hub and engine block. The wiring harness feeds the power supply to the fan clutch which comes on fully when the engine reaches peak engine temperature. The fan becomes' locked on' and rotates at engine RPM , a 1:1 Ratio. This maximizes the engine fan cooling capacity. The exact opposite occurs with a cold engine, less fan rotation helps to speed up the diesel engine warm-up.
In order to slide the fan belt out from around the fan hub this strap must be removed temporarily. Remove the single bolt on the block securing the strap and disconnect harness. Pull assembly out of the way so fan belt may be removed.Install new belt with reverse procedure. This is not a hard job, but I've seen what a broken fan belt will do to a diesel engine if not detected immediately! It's much easier in the long run to check fan belts carefully and.... If in doubt change it out!!
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