RIDEX Long Thermostat & Housing – MX-5 Mk3 NC • 316T0250

RIDEX 316T0250 Long Thermostat & Housing – MX-5 Mk3 NC

Replacement RIDEX long-type engine coolant thermostat and housing assembly for applicable Mazda MX-5 Mk3/NC 1.8 and 2.0-litre petrol models.

Critical chassis-number restriction: This long thermostat/housing is confirmed for early NC vehicles up to chassis number 115784, and for vehicles from chassis number 124658 onward.

Vehicles with chassis numbers 115785–124657 inclusive use the shorter thermostat/housing instead, RIDEX 316T0273. Do not select this component solely from registration year.

The thermostat regulates coolant flow between the engine and radiator. While the engine is cold it restricts coolant circulation through the radiator to promote faster warm-up. Once coolant reaches the calibrated operating temperature, the thermostat opens to increase radiator flow and control engine temperature.

A thermostat stuck open may cause slow warm-up, low operating temperature and poor heater performance. A thermostat stuck closed can cause overheating and excessive cooling-system pressure and may lead to serious engine damage if ignored.

• Part type: Engine coolant thermostat with housing
• Design: Long-type MX-5 NC thermostat housing
• Opening temperature: 82°C
• Diameter 2: 32.5 mm
• Housing height: 40 mm
• Housing material: Synthetic material / plastic
• Seal: Included
• Number of connections: 2
• Approximate weight: 0.316 kg
• EAN: 4059191722136
• Quantity supplied: 1 thermostat and housing assembly with seal
• Brand: RIDEX
• Part No.: 316T0250

Fitment advice: MazSpec confirms this long housing for MX-5 NC vehicles up to chassis 115784 and from chassis 124658 onward. It applies to both 1.8 and 2.0-litre petrol applications within those chassis ranges. Always check the chassis number and compare the original thermostat housing length before ordering.

Common replacement reasons: Engine running too cold, slow warm-up, weak cabin-heater performance, overheating, unstable coolant temperature, coolant leakage around the housing or seal, or replacement during wider cooling-system servicing.

Other items to consider: Inspect coolant hoses, expansion tank, radiator, water pump, radiator cap and coolant condition. Persistent overheating should be diagnosed fully rather than assuming the thermostat is the sole cause.

Useful tools / consumables: Socket and ratchet set, torque wrench, coolant drain container, hose-clamp tools, fresh coolant of the correct specification and suitable equipment for correctly bleeding the cooling system.

Difficulty guide: DIY Difficulty: Moderate. The cooling system must be opened, refilled and bled correctly, and access around the thermostat housing can be restricted.

Why RIDEX? RIDEX cooling-system components provide a cost-effective aftermarket replacement manufactured to application-specific dimensions and temperature specifications. This assembly combines the thermostat, housing and seal in one replacement unit.

What’s in the box: One RIDEX long-type thermostat and housing assembly with seal. Coolant, hoses, fasteners and installation tools are not included unless physically supplied with the component.

Installation notes: Allow the engine to cool completely before opening the cooling system. Confirm the vehicle chassis number and compare the original housing length before dismantling. Drain sufficient coolant, disconnect the relevant hoses and remove the original housing. Clean the mating surfaces carefully and install the replacement with the supplied seal correctly seated. Tighten housing fasteners evenly to the applicable specification, refill with the correct coolant mixture and bleed the system thoroughly. Check for leaks and monitor engine temperature during warm-up.