Volvo Penta Thermostat – 21437904
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You have 30 days to request a return. All sale items are final sale.
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 Penta’s 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
What’s 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 system—if you’ve got temp spikes or inconsistent readings, this is often the root cause 👍
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.