Thermostat Kit – Fits Volvo Penta AQD40A, TMD40A, TAMD40B Diesel Engines (Replaces 3831425)
Thermostat Kit – Fits Volvo Penta AQD40A, TMD40A, TAMD40B Diesel Engines (Replaces 3831425) is backordered and will ship as soon as it is back in stock.
Couldn't load pickup availability
Worry-free returns
Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).
If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.
Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Thermostat Kit – Fits Volvo Penta AQD40A, TMD40A, TAMD40B Diesel En...
Product Details
This Thermostat Kit – Fits Volvo Penta AQD40A, TMD40A, TAMD40B Diesel Engines (Replaces 3831425) is designed for a wide range of Volvo Penta diesel marine engines, including AQD, TMD, and TAMD series models. It operates at a 76°C (169°F) opening temperature to maintain optimal engine performance in both saltwater and freshwater cooling systems.
This kit serves as a direct replacement for Volvo Penta part numbers 3831425, 467014, and 875787, as well as Sierra 18-3660.
- Engineered for direct OEM replacement installation.
- Suitable for specified Volvo Penta diesel engines.
- Includes one thermostat rated for a 76°C (169°F) opening temperature.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Volvo Penta | 3831425 |
| Volvo Penta | 467014 |
| Volvo Penta | 875787 |
| Sierra | 18-3660 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This thermostat is compatible with the following Volvo Penta diesel engines. Please verify your specific model against the list to ensure proper fitment.
| Brand | Model | Stroke | OEM Part No. | Notes |
|---|---|---|---|---|
| Volvo Penta | AQD40A | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | TMD40A | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | TAMD40B | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | AQAD30A | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | AQAD41A | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | AQAD41B | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | AQD70 | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | MD100 | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | MD120 | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | MD30A | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | MD40A | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | MD70 | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | TAMD30A | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | TAMD40A | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | TAMD60 | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | TAMD70 | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | THAMD70 | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | TMD100A | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | TMD100C | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | TMD30A | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | TMD40B | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | TMD40C | 4-Stroke | 3831425 | Diesel engine |
| Volvo Penta | TMD70 | 4-Stroke | 3831425 | Diesel engine |
Technical Specs
- Product Type
- Marine Engine Thermostat Kit
- Installation
- Direct OEM replacement
- Fuel Type
- Diesel
- Opening Temperature
- 76°C (169°F)
- Operating Temperature
- 76°C (169°F) opening temperature
What’s in the Box
- 1 x Thermostat (3831425/467014/875787)
Installation Notes
- Ensure the engine is completely cool and disconnect the battery terminals.
- Drain the engine coolant into a suitable container.
- Locate the thermostat housing on the engine and carefully remove the bolts or screws.
- Remove the old thermostat and gasket. Note the thermostat's orientation.
- Thoroughly clean the mating surfaces of the housing and engine block, removing all old gasket material.
- Install the new thermostat in the correct orientation. A new gasket (sold separately) is required.
- Re-install the thermostat housing and tighten the bolts to the manufacturer's specified torque.
- Refill the cooling system with the appropriate type and amount of coolant.
- Reconnect the battery, start the engine, and check for leaks as it warms up to operating temperature.
Troubleshooting & FAQ
How do I know if my thermostat is failing?
Common signs of a faulty thermostat include engine overheating (temperature gauge reads high), the engine not reaching normal operating temperature (running too cool), or sudden fluctuations in engine temperature. You may also notice coolant leaks around the thermostat housing.
Why is maintaining the correct engine temperature important?
Operating at the correct temperature—in this case, 76°C (169°F)—ensures optimal fuel efficiency, reduces engine wear, and minimizes emissions. A thermostat that is stuck open will cause the engine to run too cool, while one that is stuck closed will lead to overheating.
Does this kit include a gasket?
This kit includes the thermostat as pictured. Gaskets are typically required for installation but are sold separately unless explicitly stated in the "What's in the Box" section. Always use a new gasket when replacing a thermostat to ensure a proper seal.
Is this the correct thermostat for my engine if my model isn't listed?
If your exact engine model is not listed in the compatibility table, do not assume fitment. We advise checking your engine's service manual for the correct OEM part number and cross-referencing it with the numbers in our Part Number Matrix.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost?
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns?
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
Payment & Security
Payment methods
Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.
