What the Cummins 6BT Fan Drive Belt does
The fan drive belt turns the radiator fan and, on most sets, the charging alternator. Cummins 6BT generator sets use either a ribbed poly-V belt with an automatic tensioner or a matched set of V-belts, depending on the fan drive.
A worn belt, or a tensioner at the end of its travel, lets the fan slow under load — one of the commonest causes of high-temperature shutdowns on otherwise healthy engines.
Signs it needs replacing
- Cracks across the ribs, missing chunks or glazing.
- Squeal on start-up, or the tensioner arm at its end stop.
- High coolant temperature under load.
- Charging fault on the controller.
Get the right part first time
Send us these on WhatsApp and our engineers will confirm the exact part before you pay:
- Belt markings, or a photo of the fan drive and belt route.
- Engine serial / CPL number.
Fitting notes
Note the belt routing before removing it. Check the tensioner and idler pulleys spin freely and quietly; a worn tensioner shortens the life of a new belt. V-belt sets are always replaced as a matched set.
Frequently asked questions
Poly-V or V-belt — which does my set use?+
It depends on the fan drive fitted. Send us a photo of the belt and pulleys and we will supply the right one.
Should the tensioner be replaced too?+
If it is noisy, rough or at the end of its travel, yes — otherwise the new belt will wear quickly.
Can a belt cause overheating?+
Yes. A slipping belt slows the fan just when the engine needs the most cooling.