BGA Rear Main Crankshaft Oil Seal – MX-5 MK1 & MK2 (1989–2005) • OS3326

BGA OS3326 Rear Main Crankshaft Oil Seal

Replacement BGA rear main crankshaft oil seal for Mazda MX-5 MK1 / NA and MK2 / NB, including MK2.5 / NB-FL, 1.6L and 1.8L petrol models (1989–2005).

The BGA OS3326 is an aftermarket replacement rear crankshaft oil seal designed to prevent engine oil escaping from the rear of the engine where the crankshaft passes through the engine housing.

Located at the gearbox end of the crankshaft, behind the flywheel or automatic transmission driveplate, the rear main oil seal maintains an oil-tight seal around the rotating crankshaft while allowing it to operate freely.

Over time, crankshaft oil seals can deteriorate through age, heat exposure, general wear or damage. A worn rear main seal may allow engine oil to leak into the bellhousing area or appear around the engine-to-gearbox joint. On manual vehicles, significant leaks can also contaminate the clutch assembly, potentially causing clutch slipping or judder.

Manufactured using NBR (nitrile butadiene rubber), the BGA OS3326 provides a replacement sealing component for supported Mazda B6 and BP engines. Its 83mm internal diameter, 100mm external diameter and 9mm width correspond to the specified rear crankshaft sealing arrangement.

The seal is particularly worth replacing during clutch replacement, flywheel removal, gearbox removal or engine rebuilding, when access to the rear crankshaft area is already available.

Product features and specifications:

• Product type: Rear main crankshaft oil seal
• Primary use: Preventing engine oil leakage around the rear crankshaft
• Location / system: Engine crankshaft / lubrication system
• Fitting position: Rear of engine / gearbox side
• Material: NBR (nitrile butadiene rubber)
• Inner diameter: 83mm
• Outer diameter: 100mm
• Width / thickness: 9mm
• Application: Selected Mazda MX-5 MK1 / NA, MK2 / NB and MK2.5 / NB-FL engines
• Engine families: 1.6L B6 and 1.8L BP petrol engines
• Quantity per vehicle: 1
• Quantity supplied: 1 rear crankshaft oil seal
• Brand: BGA (BG Automotive)
• Manufacturer Part No.: OS3326
• EAN: 5038205298408
• Mazda OE references: B630-11-312, BP05-11-312, BP05-11-315

Common failure symptoms: A worn or damaged rear crankshaft oil seal can cause oil leakage around the engine-to-gearbox joint, oil accumulation inside the transmission bellhousing or contamination of clutch components. These symptoms can also result from other engine or gearbox sealing faults, so identifying the source of the leak before replacement is important.

Fitment advice: Designed for Mazda MX-5 engines using the specified 83mm × 100mm × 9mm rear crankshaft oil seal arrangement. This is the rear, transmission-side crankshaft seal and must not be confused with the smaller front crankshaft oil seal fitted behind the crankshaft pulley. For imported, modified or previously repaired vehicles, matching the original seal dimensions and OE reference is recommended before ordering.

Other items to consider: When replacing the rear crankshaft oil seal, you may also want to consider purchasing a clutch kit, clutch release bearing, pilot bearing, flywheel bolts, appropriate gearbox oil and other rear engine sealing components required during the repair.

Useful tools / consumables: Socket set, torque wrench, suitable crankshaft seal installation tool, engine or transmission support equipment, lifting equipment, cleaning cloths and appropriate engine assembly lubricant.

Difficulty guide: DIY Difficulty: Advanced. Replacement normally requires removal of the gearbox, followed by removal of the clutch and flywheel on manual vehicles or the relevant driveplate components on automatic vehicles. Correct seal installation, flywheel or driveplate refitting and transmission alignment procedures are essential.

Why BGA? BG Automotive is an established aftermarket engine components supplier producing a comprehensive range of oil seals, gaskets, timing components and engine repair parts. The OS3326 provides an aftermarket replacement sealing component for supported Mazda engine applications, making it suitable for routine engine repairs and more extensive rebuild work.

What's in the box: 1 × BGA OS3326 Rear Main Crankshaft Oil Seal.

Installation / service notes: Remove the gearbox and associated flywheel or driveplate components as required to access the rear crankshaft seal. Carefully remove the existing seal without damaging the crankshaft or surrounding housing. Thoroughly clean and inspect the sealing surfaces and check the crankshaft for wear or scoring. Install the replacement seal squarely using an appropriate fitting tool, observing the correct orientation, seating depth and lubrication requirements for the seal design. Refit removed components following the vehicle manufacturer's tightening sequences and torque specifications. Check for engine oil leakage after reassembly and during initial operation.