Thermostat Kit – Fits Volvo Penta AQD40A, TMD40A, TAMD40B Diesel Engines (Replaces 3831425)

Thermostat Kit – Fits Volvo Penta AQD40A, TMD40A, TAMD40B Diesel Engines (Replaces 3831425)

This thermostat kit is designed for a wide range of Volvo Penta diesel marine engines, including the AQD, TMD, and TAMD series. Operating at a precise 76°C (169°F), it ensures your engine maintains its optimal temperature for performance and longevity in both saltwater and freshwater cooling systems.

This kit is a direct replacement for Volvo Penta part numbers 3831425, 467014, and 875787, as well as Sierra 18-3660.

• Fuel Type Compatibility: Diesel
• Included Components: 1 x Thermostat with Gasket/Seal
• Installation Method: Direct OEM-style fit

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below.

Technical Specifications

Package Contents

1 x Thermostat (Replaces 3831425/467014/875787)

Installation Guide

1. Safety First: Ensure the engine is completely cool and disconnect the battery terminals.
2. Drain Coolant: Place a container under the engine's drain petcock and drain the cooling system to a level below the thermostat housing.
3. Locate Housing: Identify the thermostat housing, typically located where the main coolant hose from the heat exchanger connects to the engine block.
4. Remove Housing: Loosen and remove the bolts securing the housing cover. Gently tap it if stuck, but do not pry on the mating surfaces.
5. Extract Old Thermostat: Note the orientation of the old thermostat before removing it and its gasket or seal.
6. Clean Surfaces: Thoroughly clean both the housing and engine block mating surfaces. Remove all traces of old gasket material.
7. Install New Thermostat: Place the new thermostat into the housing in the correct orientation. Ensure the new gasket or seal is properly seated.
8. Reassemble: Re-attach the housing cover and tighten the bolts to the manufacturer's recommended torque specification.
9. Refill System: Close the drain and refill the cooling system with the appropriate coolant mixture.
10. Check for Leaks: Reconnect the battery, start the engine, and let it warm up. Carefully inspect for any leaks around the thermostat housing.

Troubleshooting & FAQ

How do I confirm this thermostat fits my Volvo Penta engine?
Verify your engine model is listed in the "Compatible Engine Models" table. Additionally, cross-reference your existing part number with those in the "Part Number Cross-Reference" section to ensure a match.

What are the common signs of a failing thermostat?
Symptoms include the engine overheating, running colder than normal, erratic temperature gauge readings, or coolant leaks from the housing area. A stuck-open thermostat will prevent the engine from reaching operating temperature, while a stuck-closed one will cause overheating.

What temperature does this thermostat operate at?
This thermostat is calibrated to begin opening at 76°C (169°F) to regulate the engine's operating temperature.

OEM vs. Aftermarket?
This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

How fast do you ship and how much does it cost?
We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

What is your warranty and return policy?
This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.