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Mk7 Fiesta ST PCV / Crankcase Oil Breather System

The mountune Oil Breather System is the most functional and seamlessly integrated kit available on the market for all Mk7 Fiesta ST.

Based on the market-leading Radium kit, the mountune exclusive version further upgrades this premium oil breather system by replacing all oil hoses with high-quality braided black race versions, utilising Aeroquip-style black anodised race fittings throughout for the ultimate performance and packaged installation.

The oil breather kits are available as a combined kit including both a PCV side and Crankcase side system.

They do NOT vent to atmosphere (VTA), so comply with most basic emission requirements and are safe to use on the race track too.

The mountune Radium breather system removes the oil and sludge from the PCV gasses before it's routed to the engine to be burned. A closed loop system, like this, also promotes negative crankcase pressure for optimal performance. Furthermore, closed systems prevent unwanted oil vapors from entering the cabin.

The dipsticks built into the catch cans allow easy inspection of accumulated fluid and require no cutting, drilling or permanent modification to the vehicle during installation.


  • Effectively raises the octane and increased engine performance from cleaner inlet air
  • Prevents oil buildup in the intake and intercooler system walls, throttle body, intake manifold, etc.
  • Lowers hydrocarbon emissions
  • Capacity: 170ml each
  • Provides early indication of potential engine damage 
Each kit features the following:
  • Anodised oil catch can with integrated condenser and dipstick
  • Anodised aluminum Fiesta specific mounting bracket
  • Anodised aluminum Aeroquip style race fittings and high-performance lines
  • Stainless steel mounting hardware

PCV Breather Kit - secures to the front offside engine mount and the entire kit fits under the OEM engine cover with no modifications required. This catch can runs inline with the PCV (positive crankcase ventilation) valve and retains it's factory function. When the intake manifold pressure is close to or greater than atmospheric pressure, the PCV "check" valve closes and, thus, this hose experiences no flow.

Conversely, the PCV hose will experience "metered" vacuum when the engine is idling, steady state cruising, and decelerating. This would normally draw unwanted crankcase vapour, unspent fuel, and oil sludge into the intake manifold immediately after a high load run. Because the Radium catch cans are pressure sealed, they are great for turbocharged applications, so intake manifold connection is permitted.

Crankcase Breather Kit - secures to the 2 ECU mounting studs in the back nearside of the engine bay via a bespoke mountune catch can mount, enabling installation on all EU-build cars running a Thatcham ECU shield.

The entire kit fits under the OEM engine cover with no modifications required. This catch can runs inline with the crankcase vent port. At low loads it experiences atmospheric pressure, but when the engine is at high load (WOT), this hose will experience high flow out of the crankcase. This would normally lead to oil and sludge accumulation in the air filter intake pipe. Oil accumulation will occur in the intercooler which lowers the thermal efficiency properties of the heat exchanger and leads to decreased performance.

Customer Reviews
5.0 Based on 8 Reviews
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Filter Reviews:
    Matt S.
    United Kingdom United Kingdom
    PCV/Crankcase dual oil breather system

    Fitted the Mountune PCV/Crankcase dual oil breather system around a week ago, and I must say it’s a superb piece of kit, build quality is of the highest standard, everything fits perfectly to leave the factory finish you always get with mountune parts.

    Sandro B.
    Switzerland Switzerland
    Great stuff

    The delivery was quick as usual and all the parts were wrapped carefully. The quality of the catch cans, fittings and hoses is absolutely on top. Installation was easy enough to do it in the driveway. There is an installationguide for RH drive on the radium website. I don't know yet how much oil they will catch. I need to drive some more kilometres first. I absolutely love the way it looks in the enginebay. Would definitly recommend.

    mountune Mk7 Fiesta ST PCV / Crankcase Oil Breather System Reviewmountune Mk7 Fiesta ST PCV / Crankcase Oil Breather System Reviewmountune Mk7 Fiesta ST PCV / Crankcase Oil Breather System Review
    Joel B.
    United Kingdom United Kingdom
    Great piece of kit!

    Fantastic customer service from Mountune. Expensive but once you see and feel the quality it’s well worth the money - excellent race hoses. Pretty easy installation. It’s a shame it’s hidden under the engine cover as it looks so good! Highly recommend and would certainly buy again!

    mountune Mk7 Fiesta ST PCV / Crankcase Oil Breather System Reviewmountune Mk7 Fiesta ST PCV / Crankcase Oil Breather System Review