Blog 6: BMW MINI B38 B48 Vanos Cam Gear Drivetrain Fault
As the BMW MINI B38 B48 engines get into the higher miles we are starting to see an increasing volume come through the workshop with the same faults present. Initially the car may behave normally but display a drivetrain error depending on the extent of the failure and if the debris has travelled into the vanos gears. It is vital to get this repaired before further engine damage occurs.
We have seen this failure occur at less than 20k miles!
What Does a Vanos Gear Do?
The vanos gears advance or retard camshaft timing hydraulically, using engine oil pressure, controlled by vanos solenoids. The vanos gears are vital to an engines performance, fuel efficiency and driveability.
The B38 B48 uses double vanos, meaning there are two vanos gears, one for the intake and one for the exhaust. Each gear is mounted on the camshaft, behind the timing chain.
Warning Signs of Vanos Failure
Engine rattle.
Rough idle.
Sluggish power delivery.
Reduced fuel economy.
Check Engine Light.
Typical fault codes
Camshaft timing over-advanced / over-retarded.
Camshaft–crankshaft correlation errors.
VANOS mechanical stop/jamming faults.
Common Failure of Vanos System
The B38/B48 VANOS gear issues often stem from a specific failure where the internal filter screen on the exhaust side's VANOS sprocket bolt breaks, sending debris into the mechanism, causing it to jam, triggering fault codes, and leading to power loss, rough idling, and poor performance.
The above photos show the difference between the new central valve bolt and the original where the mesh screen has failed with debris causing internal damage to the vanos gears.
Vanos System Repair
The typical repair for this issue includes replacing both vanos cam gears, both central valve bolts and associated gaskets. This procedure requires various special tools and it is vital that original parts are used here, there are many cheaper parts available that simply do not work or fail prematurely.
Our experienced technicians follow BMW’s exact procedures, ensuring your engine is repaired perfectly and runs like new.
Whether you drive a 320d or M3, we’ve got the expertise and tools to get the job done right.
Catching problems early can save you thousands in repair bills and keep your BMW performing as it should.
📍 Book your vehicle in today with BM Performance — your trusted BMW MINI specialist.
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