Genuine Mazda Engine Coolant Thermostat & Short Housing • L336-15-170

Genuine Mazda L336-15-170 Engine Coolant Thermostat & Short Housing

Replacement Genuine Mazda short-type thermostat and housing assembly for selected Mazda MX-5 Mk3 NC models within chassis-number range 115785 to 124657 inclusive.

The thermostat regulates coolant circulation between the engine and radiator. It remains closed while the engine warms up, then opens as coolant temperature rises to maintain the correct operating temperature.

This component incorporates the thermostat, plastic water-inlet housing and sealing gasket as one replacement assembly. One assembly is fitted per vehicle.

A thermostat that sticks open can cause the engine to warm up slowly or fail to reach normal operating temperature. A thermostat that remains closed can restrict coolant circulation and cause rapid overheating.

Important fitment restriction: Mazda used different thermostat-housing lengths within the MX-5 NC range. L336-15-170 is the short-type assembly confirmed for chassis numbers 115785 to 124657 inclusive. Other NC vehicles may require the longer housing, so compare the original assembly and confirm the chassis number before ordering.

• Part type: Engine coolant thermostat and housing assembly
• Common names: Coolant thermostat / thermostat unit / water-inlet housing
• Mazda catalogue description: Thermostat & Cover
• Housing type: Short version
• Location: Engine cooling-system water inlet
• Function: Controls coolant flow and engine operating temperature
• Thermostat included: Yes
• Plastic housing included: Yes
• Sealing gasket included: Yes
• Temperature sensor included: No, unless physically supplied
• Quantity fitted per vehicle: 1
• Quantity supplied: 1 complete assembly
• Confirmed MX-5 chassis range: 115785 to 124657 inclusive
• Brand: Genuine Mazda
• Part No.: L336-15-170

Possible signs of thermostat failure:

• Engine takes unusually long to reach operating temperature
• Temperature gauge remains below its normal position
• Cabin heater output remains weak
• Fuel consumption increases because the engine remains cold
• Engine temperature rises rapidly or overheats
• Coolant circulation appears restricted
• Coolant leaking from the thermostat housing or seal
• Plastic housing cracked or distorted

Fitment advice: Do not select this thermostat solely by model year. Confirm that the vehicle falls within chassis-number range 115785 to 124657 and that the original component uses the short housing. Some early and later NC vehicles use a different-length assembly.

Replacement advice: The cooling system must be drained sufficiently before removing the housing. Inspect the mating surface, adjoining coolant hoses and hose clamps before installation. Contaminated or aged coolant should be replaced rather than reused.

Other items to consider: Inspect the radiator hoses, heater hoses, expansion tank, pressure cap, water pump, radiator and cooling fans. Consider purchasing fresh Mazda-compatible coolant and replacement hose clamps where the originals are corroded or weakened.

Useful tools / consumables: Drain container, socket set, hose-clamp pliers, gasket-surface cleaning tools, calibrated torque wrench, fresh Mazda-compatible coolant and suitable equipment for bleeding the cooling system.

Difficulty guide: DIY Difficulty: Moderate. Access is generally manageable, but the cooling system must be drained, refilled and bled correctly. Incorrect bleeding can leave trapped air and cause overheating.

Why Genuine Mazda? Genuine Mazda thermostat assemblies match the original opening characteristics, housing dimensions, hose connections and sealing profile. Correct temperature regulation is essential for engine efficiency, heater performance and protection against overheating.

What’s in the box: One Genuine Mazda short-type engine coolant thermostat and housing assembly with sealing gasket, part number L336-15-170.

Installation notes: Allow the engine to cool completely before opening the cooling system. Drain the coolant to below the thermostat level and remove the connected hose and housing fasteners. Clean the mating surface without damaging it and compare the new housing length and connections with the original component. Install the assembly with its supplied seal and tighten the fasteners evenly to the applicable Mazda specification. Reconnect the hose securely, refill with the correct coolant mixture and bleed the cooling system thoroughly. Confirm stable operating temperature, heater output and the absence of leaks before returning the vehicle to service.