Genuine Mazda Coolant Expansion Tank / Sub‑Radiator Tank • LFG1-15-350C

Genuine Mazda LFG1-15-350C Coolant Expansion Tank / Sub-Radiator Tank

Replacement Genuine Mazda coolant expansion tank / sub-radiator tank for Mazda MX-5 Mk3 / Mk3.5 / Mk3.75 (NC) models. This is the plastic coolant reservoir located in the engine bay and forms part of the vehicle’s cooling system.

The tank allows coolant to expand and return as the engine heats up and cools down, helping maintain the correct coolant level and stable cooling system operation. A failing expansion tank can lead to coolant loss, overheating risk, pressure loss, or visible coolant staining around the tank, cap or hose connections.

There is typically one coolant expansion / sub-radiator tank fitted per vehicle. It is usually found in the front engine bay area and connects into the cooling system via coolant hoses. The MX-5 NC uses this reservoir as part of the factory coolant expansion and recovery system.

This part is commonly replaced when the original plastic tank becomes yellowed, brittle, cracked, swollen, leaking from the seams, or damaged around the cap neck or hose outlets. On older MX-5 NC vehicles, preventative replacement is often worthwhile if the original tank shows heavy discolouration or age-related plastic fatigue.

• Part type: Coolant expansion tank / sub-radiator tank / coolant reservoir
• Primary use: Engine cooling system reservoir
• Location: Engine bay cooling system
• Quantity per vehicle: 1
• Brand: Genuine Mazda
• Part No.: LFG1-15-350C
• Also referenced as: LFG115350C
• Supersedes: LFG1-15-350A / LFG1-15-350B
• Designed for Mazda MX-5 Mk3 / Mk3.5 / Mk3.75 (NC) applications

Fitment advice: Designed for the Mazda MX-5 NC variants listed in the compatibility table, covering Mk3, Mk3.5 and Mk3.75 soft-top and Roadster Coupe / PRHT models with 1.8 and 2.0 petrol engines. For imported, modified or previously repaired cars, matching the part number on the original tank is the best way to confirm the correct reservoir style before fitting.

Other items to consider: When changing this part, you may also want to consider purchasing related items such as coolant hoses, hose clips/clamps, radiator cap, fresh Mazda-approved coolant, or any mounting hardware that may be corroded, brittle or difficult to reuse.

Useful tools / consumables: Basic hand tools, hose clamp pliers, drain tray, funnel, suitable Mazda-approved coolant, protective gloves, workshop towels and, ideally, a cooling system pressure tester for checking leaks after installation.

Difficulty guide: DIY Difficulty: Moderate. The tank itself is generally accessible, but the cooling system may need to be partially drained, refilled and bled correctly. Always work on the cooling system only when the engine is completely cold.

Why Genuine Mazda? Genuine Mazda components are designed to match the original specification of the vehicle. For coolant reservoirs, this means correct fitment, hose alignment, cap seating, material quality, heat resistance and compatibility with the original cooling system layout. Genuine Mazda parts reduce the risk of poor fit, premature cracking, incorrect hose positioning or sealing issues that can occur with lower-quality pattern parts.

Why buy from Mazspec? Mazspec specialises in Mazda parts and understands the common issues these vehicles develop as they age. We source genuine Mazda components through trusted OE channels and can help with fitment support, related parts advice and practical technical guidance before you order.

What’s in the box: One Genuine Mazda coolant expansion tank / sub-radiator tank.

Installation notes: Always install with the engine cold. Inspect connected hoses and clips before refitting, refill with the correct Mazda-approved coolant mixture, bleed the cooling system as required and check carefully for leaks after installation.