Genuine Mazda Engine Oil Cooler Retaining Bolt • LF9V-14-789

Genuine Mazda Engine Oil Cooler Retaining Bolt

Replacement Genuine Mazda oil-cooler retaining bolt for Mazda MX-5 Mk3.5 and Mk3.75 NC models fitted with the later-style engine-oil cooler.

The bolt passes through the centre of the water-to-oil heat exchanger and secures the cooler to the oil-filter housing. Correct retention is essential because the assembly carries pressurised engine oil and forms part of the engine-cooling circuit.

Mazda revised the MX-5 NC oil-cooler arrangement for the Mk3.5 generation. This retaining bolt is used with that later cooler and housing configuration on both 1.8- and 2.0-litre engines.

One bolt is used per oil-cooler installation, and this listing supplies one Genuine Mazda retaining bolt.

Earlier-model conversion: This bolt may also be required when converting an earlier Mk3 NC engine to the later Mk3.5-style oil cooler. The compatible later oil cooler, oil-filter housing and associated seals must also be present; the bolt alone does not form a complete conversion kit.

• Part type: Engine oil-cooler retaining bolt
• Common names: Oil-cooler centre bolt / fixing bolt / cooler mounting bolt
• Mazda catalogue description: Bolt, Oil Cooler
• Installation position: Through the centre of the engine oil cooler
• Mounting location: Oil-cooler and oil-filter-housing assembly
• Function: Clamps the oil cooler securely to the oil-filter housing
• Oil-cooler type: Later water-to-oil heat exchanger arrangement
• Engine application: 1.8- and 2.0-litre petrol engines with the later cooler arrangement
• Quantity fitted per vehicle: 1
• Quantity supplied: 1 bolt
• Oil cooler included: No
• Oil-filter housing included: No
• Seals or O-rings included: No
• Oil filter included: No
• Brand: Genuine Mazda
• Part No.: LF9V-14-789
• MX-5 fitment: Mk3.5 and Mk3.75 NC models, 2009–2015

Typical reasons for replacement:

• Original bolt damaged during oil-cooler removal
• Threads worn, corroded or cross-threaded
• Bolt head damaged by incorrect tools
• Original fixing missing following engine work
• Oil cooler or oil-filter housing being replaced
• Later-style oil cooler being fitted to an earlier NC engine
• Oil leakage requiring dismantling of the cooler assembly

Fitment advice: Confirm that the vehicle has the later-style oil cooler and corresponding oil-filter housing. Early Mk3 NC vehicles use a different cooler arrangement unless they have previously been converted.

Conversion advice: When upgrading an early NC to the later oil cooler, the correct Mazda oil-filter housing, cooler assembly, seals and related coolant connections must be used. This listing supplies only the retaining bolt.

Seal inspection: Replace any disturbed oil-cooler seals or O-rings as required. Reusing flattened, hardened or damaged seals can cause engine-oil or coolant leakage after reassembly.

Thread inspection: Inspect the threads in the oil-filter housing before installation. A new bolt will not repair damaged, contaminated or previously cross-threaded housing threads.

Oil-system advice: Prevent dirt, old seal material and coolant from entering the oil passages while the cooler is removed. Renew the engine oil and filter where contamination may have occurred.

Other items to inspect: Check the oil cooler, oil-filter housing, oil-pressure switch area, coolant hoses, hose clamps and sealing faces while the assembly is dismantled.

Useful tools / consumables: Correct-size socket, calibrated torque wrench, drain containers, suitable parts cleaner, lint-free cloths, replacement seals, engine oil, oil filter and coolant as required.

Difficulty guide: DIY Difficulty: Moderate. Access requires draining or controlling engine oil and coolant, removing the oil filter and carefully dismantling the cooler assembly.

Why Genuine Mazda? Genuine Mazda retaining hardware matches the original thread, shank length, seating arrangement and oil-cooler assembly dimensions. Correct fit helps clamp the cooler evenly without substituting unsuitable general-purpose hardware.

What’s in the box: One Genuine Mazda engine oil-cooler retaining bolt, part number LF9V-14-789.

Installation notes: Allow the engine to cool and drain or control the engine oil and coolant as required. Remove the oil filter and dismantle the cooler following the applicable Mazda workshop procedure. Clean the mating surfaces and inspect all threads and seals. Position the cooler correctly, install the retaining bolt by hand to prevent cross-threading and tighten it using the specified Mazda procedure. Refit the oil filter, refill all drained fluids and check carefully for oil and coolant leakage after running the engine.