Volvo Penta Thermostat 21437904

The Volvo Penta 21437904 Thermostat is a genuine OEM cooling system component engineered for precise temperature regulation in Volvo Penta marine engines.

This thermostat uses an advanced wax-element mechanism to control coolant flow based on engine temperature. As the engine warms, the internal element expands, opening the valve to allow coolant circulation and maintain optimal operating conditions. This ensures proper combustion efficiency, stable oil viscosity, and protection of critical internal engine components.

Designed with modern Volvo Penta cooling system architecture, this thermostat incorporates bleed notches and internal check features to help purge air from the system, improving cooling efficiency and preventing hot spots. Stainless steel internal components and a robust housing provide long service life in both freshwater and saltwater environments.

Built to Volvo Pentas exact specifications, this unit delivers consistent opening characteristics, reliable performance under load, and exact OEM fitment.

Key Features

• Genuine Volvo Penta OEM thermostat
• Precision wax-element temperature control
• Integrated bleed design to reduce air pockets
• Maintains optimal engine operating temperature
• Prevents overheating and cold-running conditions
• Durable stainless steel and brass construction
• Designed for modern Volvo Penta cooling systems
• Direct OEM replacement no modification required

Engine Compatibility

Volvo Penta Marine Engines

Used across a range of modern Volvo Penta platforms, including:

Diesel Engines

• Volvo Penta D3 series
• Volvo Penta D4 series
• Volvo Penta D6 series

Gasoline Engines (select late-model platforms)

• Volvo Penta V6 and V8 engines (application dependent)

Commonly found in modern sterndrive and inboard Volvo Penta cooling systems

Serial Number Fitment Notice

Fitment depends on:

• Engine model and variant
• Production year
• Cooling system design

Always confirm compatibility using your engine serial number before ordering.

Specifications

• Part Number: 21437904
• Type: Engine thermostat
• Function: Regulates coolant flow and engine temperature
• Operation: Wax-element, spring-loaded valve
• Construction:
  • Stainless steel internal components
  • Brass thermal element
• Design Features:
  • Integrated bleed / air purge features
  • High-efficiency coolant flow control

Whats Included

• Thermostat (seal/gasket sold separately unless specified)

When This Part Needs Replacement

Replace the thermostat if you experience:

• Engine overheating
• Engine running below proper temperature
• Fluctuating or unstable temperature readings
• Delayed warm-up
• Reduced fuel efficiency or performance

Installation Notes

• Replace sealing O-ring or gasket during installation
• Install with correct orientation (spring toward engine)
• Inspect housing and cooling passages for debris
• Bleed cooling system if applicable
• Verify operating temperature after installation

Alternate / Superseded Part Numbers

OEM Cross References

• Volvo Penta: 21437904

Shipping

Shipping: Ships same or next day for fast Canada wide shipping.

Parts Desk Insight

These newer Volvo thermostats are designed to manage air in the cooling systemif youve got temp spikes or inconsistent readings, this is often the root cause