What the Perkins 1004 Fan Belt (V-Belt) does
On Perkins 1004 engines the V-belt drives the cooling fan and the charging alternator. A slipping belt slows the fan — the engine overheats under load — and undercharges the battery, so the next start fails.
Belts harden and crack with heat and age even on sets that run little. Checking condition and tension is part of every service visit.
Signs it needs replacing
- Cracks across the belt, glazed shiny sides, or frayed edges.
- Squealing on start-up or under load.
- High coolant temperature under load.
- Battery not charging; charge warning 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:
- The size markings printed on your old belt.
- A photo of the engine dataplate — the engine serial number decides the exact part.
Fitting notes
Fit over the pulleys without levering, then tension to specification — too loose and it slips, too tight and it wears the water pump and alternator bearings. Recheck tension after the first hours of running.
Frequently asked questions
How often should the fan belt be replaced?+
Whenever it shows cracks, glazing or fraying, or it cannot be tensioned correctly. Keep a spare on site for critical sets.
Can a loose belt cause a flat battery?+
Yes — it slips on the charging alternator pulley, so the battery is not recharged after starting.
How tight should it be?+
To the engine manufacturer's tension specification. As a rough check, there should be only slight deflection when pressed midway on the longest run.