3831425 Thermostat Replacement for Volvo Penta AQAD30A AQAD41A AQAD41B AQD40A AQD70 MD100 MD120 MD30A MD40A MD70 TAMD30A TAMD40A TAMD40B TAMD60 TAMD70 THAMD70 TMD100A TMD100C TMD30A TMD40A TMD40B TMD40C TMD70 | JLM Marine

Thermostat Replacement for Volvo Penta AQAD30A AQAD41A AQAD41B AQD40A AQD70 MD100 MD120 MD30A MD40A MD70 TAMD30A TAMD40A TAMD40B TAMD60 TAMD70 THAMD70 TMD100A TMD100C TMD30A TMD40A TMD40B TMD40C TMD70

This thermostat replacement kit is engineered for a wide range of Volvo Penta diesel marine engines, including the AQAD, AQD, MD, TAMD, THAMD, and TMD series. Designed to maintain optimal operating temperature, this service kit ensures reliable performance across multiple engine models from small to large displacement units.

This aftermarket thermostat directly replaces OEM part number 3831425, providing a cost-effective solution for routine maintenance and engine cooling system repairs on Volvo Penta marine diesel engines.

• Complete thermostat service kit for diesel marine engines
• Ensures proper engine temperature regulation
• Direct replacement for OEM 3831425

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

This kit includes the following components:

• Thermostat Service Kit

Installation Guide

1. Allow the engine to cool completely before beginning work. Disconnect the battery to prevent accidental starting.
2. Drain the coolant from the cooling system into a suitable container following the manufacturer's recommended procedure. Locate the thermostat housing on your engine.
3. Remove the bolts securing the thermostat housing cover and carefully lift off the cover. Note the orientation of the old thermostat before removal.
4. Remove the old thermostat and clean all gasket material from both the housing and cover mating surfaces. Ensure surfaces are smooth and free of debris.
5. Install the new thermostat in the same orientation as the original, ensuring the temperature-sensing element faces the correct direction (typically toward the engine block).
6. Install the new gasket or seal included in the service kit. Apply a thin bead of gasket sealant if recommended by the manufacturer.
7. Reinstall the thermostat housing cover and torque the bolts to the manufacturer's specifications in a cross-pattern. Avoid over-tightening.
8. Refill the cooling system with the correct type and mixture of coolant as specified in your engine manual. Check for the proper coolant-to-water ratio.
9. Reconnect the battery and start the engine. Allow it to reach normal operating temperature while monitoring for leaks around the thermostat housing.
10. Check the coolant level once the engine has warmed up and top off if necessary. Verify that the thermostat is opening properly by monitoring engine temperature.
11. Inspect all connections and hoses for leaks or seepage. Retighten housing bolts if needed, but do not exceed specified torque.
12. Dispose of old coolant properly according to local environmental regulations. Record the replacement date and engine hours for future maintenance scheduling.

Troubleshooting & FAQ

Q: How do I confirm this thermostat fits my Volvo Penta engine?
A: Cross-reference your engine model with the compatibility table above. Verify that your engine's current thermostat matches OEM part number 3831425 by checking your parts manual or the existing component.

Q: How often should I replace the thermostat on my diesel marine engine?
A: Thermostats should typically be replaced every 2-3 years or according to your engine manufacturer's maintenance schedule. Replace immediately if you experience overheating, erratic temperature readings, or poor cabin heat.

Q: What are the signs that my thermostat is failing?
A: Common symptoms include engine overheating, fluctuating temperature gauge readings, slow warm-up times, poor cabin heating, or coolant leaks around the thermostat housing. If you notice any of these issues, inspect and test the thermostat.

Q: Can I install this thermostat myself or do I need a professional?
A: While experienced boat owners with mechanical skills can perform this replacement, we recommend professional installation to ensure proper coolant system bleeding, correct torque specifications, and leak-free operation.

Q: Is this an OEM or aftermarket thermostat?
A: 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.

Q: How fast do you ship and how much does it cost?
A: 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.

Q: What is your warranty and return policy?
A: 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.