21437904 Thermostat | Genuine Volvo Penta Part

🔧 Product Description

A coolant thermostat used in selected Volvo Penta 5.0-litre and 5.7-litre marine petrol engines equipped with full closed cooling. It regulates coolant flow through heat exchanger 21444263.

🚤 Compatibility

• Engine Family: V
• HP Range: 225-320 HP

Full model list at the end of this description.

⚙️ Key Features

• Genuine Volvo Penta closed-cooling thermostat
• Designed for freshwater-cooled V8 petrol engines
• Controls engine warm-up and operating temperature
• Used with sealing ring 416033
• Compatible with the original heat-exchanger housing
• Engine type: V8 EFI marine petrol with closed cooling

🔌 Function

Controls coolant circulation through the engine and heat exchanger to maintain the intended operating temperature.

⚠️ Common Signs of Failure

• Engine runs too hot or too cold
• Temperature fluctuates
• Slow engine warm-up
• Thermostat stuck open or closed
• Reduced cabin-heater output
• Overheating under load

🛠️ Service Notes

• Let the engine cool fully and drain coolant to below the housing before opening it, catching what comes out
• Clean both faces of the housing without scoring them, and fit a new gasket or sealing ring with the thermostat — the old seal should never be reused
• Fit the thermostat the right way round, with the sensing element towards the engine and any vent or bleed hole positioned as the original was, and check it is properly seated before the cover goes on
• Pull the housing fasteners down evenly and to the figure in the workshop manual for your engine; an unevenly tightened cover distorts and weeps
• Refill with the specified coolant, vent the system, then run up to temperature and check both for leaks and that the engine reaches and holds its normal running temperature

🔄 Supersession & Cross Reference

OEM / Related Numbers

• 416033 - thermostat sealing ring
• 21444263 - heat exchanger
• 3858995 - heat-exchanger anode

📦 Condition

• Genuine Volvo Penta part
• Brand new
• Supplied in original or equivalent packaging

🔎 Full Model Compatibility

Typically suits:

• Volvo Penta V8-270-C-B, V8-270-CE-B, V8-300-C-A, V8-300-CE-A, V8-300-C-B, V8-320-C-B, V8-320-CE-B, V8-300-CE-B, V8-320-C-A, V8-320-CE-A, V8-225-C-A, V8-225-CE-A, V8-225-C-B, V8-225-CE-B, V8-270-C-A, V8-270-CE-A
• Volvo Penta 5.7GXiC-320-R, 5.7GXiCE-320-R, 5.7GXiC-P, 5.7GXiCE-P, 5.7GiC-300-P, 5.7GiCE-300-P, 5.7GiC-300-R, 5.7GiCE-300-R, 5.0GiC-225-S, 5.0GiCE-225-S, 5.0GXiC-P, 5.0GXiCE-P, 5.0GXiC-270-R, 5.0GXiCE-270-R