Mishimoto High-Temp Thermostat

1999–2007 Dodge Ram 2500 & 3500 5.9L Diesel

Part #: MMTS-RAM-99H

Overview

The Mishimoto High-Temperature Thermostat is a premium direct-fit replacement designed specifically for Dodge Ram 2500 and 3500 trucks equipped with the 5.9L Cummins diesel engine from 1999 to 2007. This thermostat is engineered to activate at a higher temperature of 205°F, compared to the factory units, allowing your engine to reach optimal operating temperature more quickly. Faster warm-up times improve engine efficiency and reduce wear, especially in colder climates where prolonged engine warm-up is critical.

Replacing a failing or aging thermostat with this Mishimoto unit helps prevent engine overheating and costly internal damage, ensuring your truck maintains reliable cooling system performance. Backed by Mishimoto’s lifetime warranty, this thermostat is an ideal upgrade for Dodge Ram owners seeking enhanced cooling system durability and consistent temperature regulation.

Key Features

Engineered for durability and precision, the Mishimoto High-Temperature Thermostat offers several advantages over stock units:

• Higher activation temperature of 205°F for improved engine warm-up and efficiency
• Promotes quicker engine warm-up by restricting coolant flow longer during cold starts
• Direct-fit replacement requiring no modifications or special tools
• Constructed from premium-grade materials for long-lasting performance and corrosion resistance
• Ensures consistent temperature regulation to protect engine components and extend engine life
• Compatible with Dodge Ram 2500 and 3500 trucks equipped with 5.9L Cummins diesel engines (1999–2007)
• Includes Mishimoto Lifetime Warranty for superior product assurance

Construction & Design

The Mishimoto thermostat is crafted from high-quality metals designed to withstand the demanding thermal environment of diesel engines. Its robust construction ensures reliable valve operation and precise temperature control under heavy-duty conditions. Corrosion-resistant housing and internal components provide durability and consistent performance throughout the life of your vehicle. This meticulous engineering helps maintain optimal engine temperatures, preventing overheating and reducing the risk of expensive engine damage.

Installation & Fitment

This thermostat is a direct-fit replacement for the factory unit on 1999–2007 Dodge Ram 2500 and 3500 trucks equipped with the 5.9L Cummins diesel engine. Installation is straightforward and requires no special tools or modifications, making it suitable for both professional mechanics and DIY enthusiasts. Simply remove the old thermostat and install the Mishimoto unit to restore proper cooling system function and improve engine warm-up times.

What's Included

• Mishimoto High-Temperature Thermostat (Part # MMTS-RAM-99H)
• Gasket or O-ring for proper sealing
• Installation instructions

Ideal For

This thermostat is perfect for Dodge Ram 2500 and 3500 owners who want to enhance their engine’s cooling system reliability and efficiency, especially in colder climates where faster engine warm-up is beneficial. It is also an excellent choice for those replacing a faulty or aging factory thermostat to prevent overheating and maintain optimal engine performance. Whether your Ram is used for heavy-duty work, towing, or daily driving, the Mishimoto High-Temperature Thermostat provides dependable temperature control and peace of mind.

Mishimoto is a performance cooling brand offering aluminum radiators, intercoolers, oil coolers, hoses, and supporting hardware built to manage heat on hard-driven street and track vehicles. For boosted setups and towing/off-road rigs alike, Mishimoto upgrades are designed to increase cooling capacity and reliability where factory systems can become a limitation.