Water Pump Pulley Explosion – 2021 BMW M340i

Project Name: Water Pump Pulley Explosion – 2021 BMW M340i

Project Type: Residential

Location: La Mesa, CA

Duration: 2 Days

Project Cost: $2,400

Primary Service(s) Provided:

• Replacement of BMW water pump & pulley
• New radiator & fan installation
• New thermostat housing
• New tensioner, idler pulley & serpentine belt
• Full system flush and bleed
• Engine bay cleaning and testing

Project Details:

A 2021 BMW M340i was brought in after the water pump pulley completely shattered, causing the serpentine belt to come off at high speed. The broken belt then cracked the radiator and damaged the radiator fan. The thermostat housing, belt tensioner, and idler pulley were all hit and needed replacement. Coolant and rubber debris coated the engine bay, creating additional challenges.

Our team replaced all damaged components using OEM BMW parts—including the water pump, radiator, radiator fan, thermostat housing, belt tensioner, idler pulley, and serpentine belt. The cooling system was thoroughly flushed, refilled with BMW-spec coolant, and fully bled to ensure optimal operation. After a careful cleanup, we performed system tests to confirm all issues were resolved and the engine bay was spotless.