Neptune BM30 Expansion Tank Cap 2.0 Bar for BMW

Neptune BM30 Expansion Tank Cap | 2.0 Bar (BMW)

Neptune BM30 (Neptune 04108) is a black screw-on expansion tank cap rated at 2.0 bar (200 kPa), 56 mm with an internal thread – the high-pressure specification used on BMW cooling systems. A tired expansion cap is a classic cause of overheating, coolant smell and repeated top-ups on BMW models, and this Neptune replacement costs a fraction of the dealer part.

Key Features

• Genuine Neptune quality (part 04108)
• High 2.0 bar (200 kPa) rating to BMW cooling system specification
• 56 mm screw-on cap with internal thread, colour black
• Cures pressure loss, overheating and coolant top-up cycles
• Fraction of the dealership price

Specifications

• Opening pressure: 2.0 bar (200 kPa / approx. 29 psi)
• Outer diameter: 56 mm · Height: 45 mm · Colour: black
• Mounting: screw connection, internal thread
• Part reference: BM30 / Neptune 04108

Vehicle Applications | What This Cap Fits

The TecDoc parts catalogue lists 57 vehicle applications for this cap across BMW. Vehicle listings are a guide only. Always match the pressure stamping, neck size and reach of the cap you are replacing before ordering.

How to Check You Have the Right Cap

The pressure rating is printed on your original cap. Match the pressure and the cap style, or bring your old cap to our Kempton Park counter and we will match it for you. Never open a radiator or expansion cap while the engine is hot.

Radiator Cap Range at Greyhound Auto Retail

Clip-on metal caps (Neptune): RC1-13, RC1-16, RC2-13, RC2-16 and the full RC3G 60-27 family from 48 to 124 kPa. Screw-on expansion tank caps: 1.2 bar yellow (60 mm and 62 mm), 1.4 bar black, and the 2.0 bar Neptune BMW cap.

Buying oil too? Engine oil of R300 or more gets you 10% off all filters, added automatically at checkout.