VTT Billet PCV Cap Upgrade for BMW Gen 1 B58 (Valve Cover Diaphragm Fix) - F20 F21 F22 F23 F30 F31 F32 F33 F34 F36 - M140i M240i 340i 440i

Machined Alloy Breather Cap Solution for BMW B58 Gen 1 - F20 F21 F22 F23 F30 F31 F32 F33 F34 F36

Sort your B58 engine breather problems properly. This precision billet aluminium breather cap package replaces the fragile rocker cover diaphragm assembly on Gen 1 B58 engines and restores stable crankcase control under boost and vacuum. It is a proven fix for smoke at idle or after overrun, oil misting, and inconsistent manifold reference. Ideal for M140i, M240i, 340i and 440i owners who want a reliable long-term solution that copes with daily use, spirited driving and tuning.

The kit includes a CNC machined cap, a billet banjo fitting, a dedicated Vacuum Boost adapter and a hose with an integrated check valve. Together they re-route a clean manifold signal from the cylinder head ports to the intake manifold, removing the failure-prone plastic diaphragm and giving consistent sump pressure management. Expect cleaner running and fewer oil vapour issues compared with the stock setup.

Why enthusiasts choose this upgrade

• Direct replacement for the weak rocker cover breather diaphragm on Gen 1 B58 engines
• Billet aluminium components for durability under elevated boost and heat
• Restores proper crankcase depression for better blow-by control and reduced exhaust smoke
• Supplied Vacuum Boost adapter and banjo hardware ensure a secure, leak-resistant install
• Compatible with low side catch can setups and works seamlessly with VTT high side catch can kits
• Great preventative maintenance on both stock and mapped cars

What you get

• 1 x Billet breather cap
• 1 x Billet banjo fitting
• 1 x Vacuum Boost adapter
• 1 x Line with built-in check valve

How it helps

Age and heat can cause the factory breather diaphragm to split, leading to fluctuating crankcase pressure, blue or white smoke and oil consumption. This upgrade removes that weak point and provides a robust manifold reference path so the engine maintains the correct pressure balance. The result is dependable ventilation, reduced oil vapour carryover and a cleaner intake tract.

Vehicle coverage - BMW Gen 1 B58

Fits the following BMW models with the first generation B58 engine.

1 Series

• F20 LCI 09/2015 to 06/2019 - M140i and M140ix (xDrive)
• F21 LCI 09/2015 to 06/2019 - M140i and M140ix (xDrive)

2 Series

• F22 09/2015 to 06/2017 - M240i and M240ix (xDrive)
• F22 LCI 09/2016 to 12/2019 - M240i and M240ix (xDrive)
• F23 09/2015 to 06/2017 - M240i and M240ix (xDrive)
• F23 LCI 10/2016 to 12/2019 - M240i and M240ix (xDrive)

3 Series

• F30 LCI 10/2014 to 10/2018 - 340i and 340ix (xDrive)
• F31 LCI 10/2014 to 06/2019 - 340i and 340ix (xDrive)
• F34 GT LCI 09/2015 to 12/2019 - 340i and 340ix (xDrive)

4 Series

• F32 04/2015 to 02/2017 - 440i and 440ix (xDrive)
• F32 LCI 05/2016 to 12/2019 - 440i and 440ix (xDrive)
• F33 03/2015 to 02/2017 - 440i and 440ix (xDrive)
• F33 LCI 05/2016 to 12/2019 - 440i and 440ix (xDrive)
• F36 Gran Coupé 03/2015 to 02/2017 - 440i and 440ix (xDrive)
• F36 Gran Coupé LCI 05/2016 to 12/2019 - 440i and 440ix (xDrive)

Installation and support

Fitting is straightforward for experienced enthusiasts. Remove the OE cap, extract the torn diaphragm, seat the billet cap, install the Vacuum Boost adapter inline on the reference hose, then connect the supplied line and tighten the banjo hardware.

Want it installed professionally? Book workshop fitting with MJ Modifications in Warwickshire. Email info@mjmodifications.co.uk for a quote and availability.

Best paired with

For a complete B58 breathing setup we recommend adding the VTT High Side Catch Can kit and the VTT crankcase breather for maximum oil vapour control.

Real world results

We have installed this upgrade on our own builds and many customer cars. Feedback is consistently positive - cleaner running, no more smoke caused by a split diaphragm and stable crankcase control even on tuned applications.

Compatibility check

Provide your UK registration or the last 7 digits of your VIN at checkout and we will verify fitment before dispatch.

Part number

VTT-B58-PCV-CAP

Manufacturer

VTT - Vargas Turbocharger Technologies

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