1. Introduction
This manual provides essential information for the proper installation, operation, and maintenance of your AISIN THT-025 Engine Coolant Thermostat and Housing Assembly. Designed for efficient and consistent performance, this component is manufactured using high-quality materials to ensure optimal engine cooling system function. Please read this manual thoroughly before installation to ensure correct procedures and to maximize the lifespan of the product.
2. Product Features
- OE Matched Design: Engineered to provide perfect OE form, fit, and function.
- Consistent Performance: Designed for efficient and consistent engine coolant temperature regulation.
- High-Quality Materials: Manufactured using only the highest quality materials for long life and dependable cooling system performance.
- Correct Operating Temperature: Features the correct OE specified operating temperature for optimal engine efficiency.
- Integrated Housing: Includes the thermostat housing for a complete assembly.
- Vehicle Compatibility: Compatible with select Toyota Tacoma vehicles (2016-2019 models). Verify specific fitment details for your engine.
3. What's In The Box
Upon opening the package, please verify that all components are present and undamaged.
- 1 x AISIN THT-025 Engine Coolant Thermostat & Housing Assembly
Image: The AISIN THT-025 Engine Coolant Thermostat and Housing Assembly. This image shows the complete black plastic assembly with various hose connections and a brown electrical connector on top. The mounting flange with two bolt holes is visible at the bottom.
4. Setup and Installation
Disclaimer: Installation of automotive components should be performed by a qualified technician. Improper installation can lead to vehicle damage or personal injury. Always refer to your vehicle's specific service manual for detailed instructions and safety precautions.
4.1. Required Tools and Materials
- Socket Wrench Set
- Pliers
- Drain Pan
- New Engine Coolant (compatible with your vehicle)
- Gasket Scraper (if needed)
- Clean Rags
- Safety Glasses and Gloves
4.2. Installation Steps
- Safety First: Ensure the engine is completely cool before beginning work. Disconnect the negative terminal of the vehicle's battery.
- Drain Coolant: Place a drain pan under the radiator and open the drain cock to drain the engine coolant. Some coolant may also drain when hoses are disconnected from the thermostat housing.
- Locate Thermostat Housing: Identify the existing thermostat housing, typically located at the end of the upper radiator hose where it connects to the engine.
- Disconnect Hoses and Electrical Connectors: Carefully disconnect all hoses attached to the thermostat housing. If present, disconnect any electrical connectors (e.g., for temperature sensors).
- Remove Old Thermostat Housing: Unbolt the old thermostat housing from the engine. Note the orientation for reinstallation.
- Clean Mounting Surface: Thoroughly clean the engine's mounting surface, removing any old gasket material or debris. A clean surface is crucial for a proper seal.
- Install New Thermostat Housing: Position the new AISIN THT-025 assembly with its gasket (if separate) onto the engine's mounting surface. Ensure correct orientation.
- Secure Bolts: Install and tighten the mounting bolts to the manufacturer's specified torque. Do not overtighten.
- Reconnect Hoses and Electrical Connectors: Reattach all hoses securely, ensuring clamps are properly positioned. Reconnect any electrical connectors.
- Refill Coolant: Close the radiator drain cock. Refill the cooling system with the appropriate type and amount of new engine coolant.
- Bleed Air: Start the engine and allow it to reach operating temperature with the heater on full blast. Monitor the coolant level and add more as needed. Bleed any trapped air from the system according to your vehicle's service manual. This may involve opening bleed valves or repeatedly squeezing radiator hoses.
- Check for Leaks: After the engine has cooled, recheck the coolant level and inspect all connections for leaks.
- Reconnect Battery: Reconnect the negative battery terminal.
5. Operating Principles
The AISIN THT-025 thermostat is a crucial component of your vehicle's engine cooling system. Its primary function is to regulate the engine's operating temperature by controlling the flow of coolant to the radiator. When the engine is cold, the thermostat remains closed, allowing the engine to warm up quickly. Once the engine reaches its optimal operating temperature (specified by the OE manufacturer), the thermostat opens, allowing coolant to flow through the radiator to dissipate heat. This continuous regulation ensures the engine operates within its ideal temperature range, promoting efficiency and preventing overheating or undercooling.
6. Maintenance
While the AISIN THT-025 thermostat is designed for long-term reliability, proper cooling system maintenance is essential for its optimal function and longevity.
- Coolant Checks: Regularly check your engine coolant level and condition. Ensure it is at the proper level and free from contaminants.
- Coolant Flush: Follow your vehicle manufacturer's recommendations for coolant flush and replacement intervals. Old or contaminated coolant can degrade cooling system components, including the thermostat.
- Hose Inspection: Periodically inspect all cooling system hoses for cracks, leaks, or signs of deterioration. Replace any damaged hoses promptly.
- System Leaks: Address any cooling system leaks immediately. Low coolant levels can cause the engine to overheat and damage the thermostat.
7. Troubleshooting
If you experience issues with your vehicle's cooling system after installing the AISIN THT-025, consider the following common problems and solutions:
| Symptom | Possible Cause | Solution |
|---|---|---|
| Engine Overheating | Low coolant level, air in system, faulty thermostat (stuck closed), clogged radiator. | Check coolant level and top up. Bleed air from system. Inspect thermostat for proper operation (may require professional diagnosis). Check radiator for obstructions. |
| Engine Running Cold (slow to warm up) | Faulty thermostat (stuck open). | Replace thermostat. |
| Coolant Leaks around Housing | Improperly seated gasket, loose bolts, damaged housing, damaged hose or clamp. | Ensure mounting surface is clean and gasket is properly seated. Tighten bolts to specification. Inspect housing for cracks. Check hose connections and clamps. |
| Temperature Gauge Fluctuates Erratically | Air in cooling system, faulty temperature sensor, intermittent thermostat operation. | Bleed air from system. Check temperature sensor and its wiring. Professional diagnosis may be required to confirm thermostat operation. |
If troubleshooting steps do not resolve the issue, it is recommended to consult a certified automotive technician.
8. Specifications
| Attribute | Detail |
|---|---|
| Manufacturer | AISIN |
| Brand | AISIN |
| Model Number | THT-025 |
| Item Weight | 9.5 ounces |
| Package Dimensions | 6.57 x 6.3 x 3.66 inches |
| Country of Origin | Japan |
| Exterior Finish | Machined |
9. Warranty and Support
AISIN products are manufactured to high-quality standards. For specific warranty information regarding your THT-025 Engine Coolant Thermostat and Housing Assembly, please refer to the warranty documentation included with your purchase or visit the official AISIN website. For technical support or inquiries, please contact AISIN customer service through their official channels.
AISIN Official Website: www.aisin.com
