BMW B58 PCV Diaphragm/Membrane Repair Kit with Cap – Crankcase Breather Oil Separator Fix, Rocker/Valve Cover Vent Service Set – Fits M140i M240i 340i 440i 540i 740i M340i X3 M40i X4 M40i Z4 M40i Supra A90 X5 40i X6 40i X7 40i

Restore your B58 engine’s crankcase breather performance with this premium membrane repair set. Designed for the BMW B58 straight-six turbo platform, this cost‑effective fix lets you renew the breather system at the source so you do not have to replace the entire rocker cover or even remove it. Ideal for enthusiasts and professionals, it delivers an OE‑style solution that solves cracked or leaky membranes quickly and cleanly.

Our in-house team at MJ Modifications has used this part extensively and it has been a favourite with customers who want to cure ventilation issues without the expense of a full cover swap. The set includes a fresh membrane and a brand-new cover cap so you can complete the job with confidence, avoiding the common problem of brittle caps breaking during removal.

• Direct breather repair on the B58 platform without removing the rocker cover
• Includes a replacement cover cap to prevent breakage during installation
• All the components you need to replace your tired, cracked or leaking membrane
• Fast, tidy installation for DIYers and workshops
• Excellent value compared with replacing the whole rocker cover assembly

What you get:

• New breather membrane for the B58 crankcase ventilation system
• Replacement cover cap for a secure, worry‑free refit
• Supporting parts required to complete the swap

Why choose this breather repair set:

• Proven by our technicians in-house and praised by customers for reliability
• Restores proper crankcase pressure control and helps prevent unwanted leaks
• Precise fit for the B58 ventilation housing on the rocker cover

Fitting service available: For professional installation, book in with MJ Modifications in Warwickshire. Email info@mjmodifications.co.uk for a quote.

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