Genuine Mazda Long Thermostat & Housing Assembly • LF70-15-170

Genuine Mazda LF70-15-170 Long Thermostat & Housing Assembly

Replacement Genuine Mazda long-type engine coolant thermostat and housing assembly for Mazda MX-5 Mk3, Mk3.5 and Mk3.75 / NC models within the chassis-number ranges listed in the compatibility table.

The thermostat regulates coolant circulation between the engine and radiator. It remains closed while the engine warms up, then opens at the specified temperature to allow coolant to flow through the radiator and maintain the correct operating temperature.

The thermostat assembly is fitted within the engine cooling circuit where the coolant hose connects to the engine. There is one thermostat assembly fitted per vehicle. This listing supplies one Genuine Mazda thermostat, housing and sealing gasket assembly.

A thermostat that sticks open can cause slow warm-up, weak cabin heating, reduced fuel efficiency and an engine temperature gauge that remains unusually low. A thermostat that sticks closed can cause overheating, excessive cooling-system pressure and coolant loss. Cracks, distortion or leakage around the plastic housing are also common reasons for replacement.

• Part type: Long-type engine coolant thermostat and housing assembly
• Primary use: Regulates engine coolant circulation and operating temperature
• Location: Engine cooling system
• Position: Engine-side coolant outlet and hose connection
• Quantity per vehicle: 1
• Quantity supplied: 1 complete thermostat and housing assembly
• Includes: Thermostat, housing and sealing gasket
• Brand: Genuine Mazda
• Part No.: LF70-15-170
• Also referenced as: LF7015170
• Supersedes: LF50-15-170, LF50-15-170A, LF50-15-170B, LF50-15-170C, LF50-15-171, LF53-15-170, LF53-15-170A and LF53-15-170B
• Fitment note: Long-type thermostat; MX-5 fitment is restricted by chassis number as detailed in the compatibility table

Fitment advice: Mazda MX-5 NC models can use different-length thermostat assemblies. This long-type assembly is confirmed for applicable early vehicles up to chassis number 115784 and later vehicles from chassis number 124658 onwards. Vehicles between these chassis ranges require a different thermostat style. Match the vehicle chassis number and original thermostat length before installation. For imported, modified, engine-swapped or previously repaired cars, matching the original part number and component style is recommended.

Other items to consider: When changing this part, you may also want to consider purchasing fresh Mazda-compatible coolant, hose clips, associated coolant hoses, a radiator cap and replacement mounting bolts where the originals are corroded or damaged.

Useful tools / consumables: Socket set, hose-clip pliers, torque wrench, coolant drain container, funnel or cooling-system filling tool, cleaning materials and the correct Mazda-compatible coolant mixture.

Difficulty guide: DIY Difficulty: Moderate. The cooling system must be drained sufficiently, coolant hoses disconnected and the sealing surfaces cleaned carefully. The system must then be refilled and bled correctly to remove trapped air.

Why Genuine Mazda? Genuine Mazda cooling-system components are designed to match the original thermostat opening specification, housing dimensions, hose alignment, mounting points and sealing arrangement. Correct material quality and dimensional accuracy help maintain reliable coolant circulation, operating temperature control and compatibility with the surrounding cooling system.

What’s in the box: One Genuine Mazda long-type thermostat, housing and sealing gasket assembly.

Installation notes: Allow the engine to cool fully before opening the cooling system. Drain the coolant to below thermostat level, clean the mating surface and install the assembly with its supplied seal correctly seated. Tighten the mounting fasteners evenly to Mazda’s specified torque. Refill with the correct coolant mixture, bleed all trapped air and inspect the housing, hose connections and surrounding joints for leakage as the engine reaches operating temperature.