WHAT IS THE ISSUE WITH THE S55 ENGINE?
"In traditional engines the crankshaft attached to the pistons turns the camshaft(s) attached to the valves, via a belt or chain. The gears are locked in place on the crankshaft and camshafts with a keyway, so that the relationship between the pistons and valves is always the same i.e. there is no chance of the valves opening at the wrong time and hitting the pistons. This is known as the ‘timing’ of the engine.
Unfortunately BMW in their wisdom have thrown out the past 100 years of development on the internal combustion engine and instead decided to lock the crank gear to the crankshaft with nothing more than a diamond sintered washer, which offers high friction, and a load of torque from the crank bolt to hold the timing in place. In certain circumstances, a high shock load from changing gear, or harmonics over time loosening the crank bolt, the bolt moves and no longer holds the timing accurately. This may happen over time, or all at once, it seems that every engine is different as everyone’s driving style is different. When the timing goes out by a set amount, it triggers a “Drivetrain Failure” on the dashboard which results in rough running, rough idle and reduced engine performance. When the timing goes out by a further amount the ECU will actually prevent the engine from starting, because of risk of damage. We are not aware of any complete engine failures with OEM components from the crank hub slipping yet, as the ECU does seem to do a good job of shutting the engine down. However once it has slipped, the only course of action is replacement of the affected parts, as they are ‘one use’ only from BMW."
- Referenced from Litchfield Motors' Article on the S55 engine crank hub problem
WHAT IS A “KEYED CRANK HUB UPGRADE” AND WHY DO I NEED IT?
The keyed crank hub upgrade is a replacement of your stock crank hub unit with a unit that has two “keys” or “pins” for which 2 holes are drilled into the S55 crankshaft so that upon installation of the crankshaft bolt the new keyed crank hub can be locked into place permanently without a chance of relative rotation to the crankshaft. We use 2 Piece Keyed Crank Hub upgrade. This allows further insurance against the chance of the crank hub “slipping” or “spinning” and un-syncing the relative angles between the crankshaft and camshafts (this can mean engine failure which will cost upwards of $20,000 to replace or at the very least leave you stranded and un-driveable until the crank hub is replaced and engine is retimed). This SCH failure has been seen on both modified and stock S55 engines. If you are modifying your car, tracking your car, or even driving spiritedly, then upgrading your crank hub is highly recommended.
IS MY CAR ON THE LIST OF AFFECTED VEHICLES?
2015+ BMW F8X M3 / M4 (CS / GTS)
2019+ BMW F87 M2C
And any other variation of BMW models utilizing the S55 engine
WHAT WILL BE NEEDED TO REPLACE MY STOCK CRANK HUB?
Two-Piece Keyed Crank Hub Kit PURCHASE HERE!
OEM Gaskets & Parts Needed
∙ Valve Cover Gasket Set
∙ Front Crank Seal - Crankshaft Seal
∙ Bolt for Timing Chain Sprocket - Intake/Exhaust Camshaft
∙ Cover Seal for Brake Booster Vacuum Pump
∙ Oil Pan Gasket
∙ Engine Oil Pan Bolt Kit (Aluminum)
∙ Coolant / Antifreeze (Blue) (1 Gallon)
∙ Engine Oil - 5W-30 Synthetic (7 Liters)
∙ Oil Filter Kit
∙ Valve Cover R&R (8.2 hours BMW book time)
∙ Oil Pan R&R (8.4 hours BMW book time)
∙ Front Crank Seal R&R (5.6 hours BMW book time)
∙ Drilling Crankshaft (1.5 hours approximated)
∙ Crank Hub R&R w/ proper torquing procedure and retiming engine (1.5 hours approximated)
Total Approximate Labor Hours: 25.2 Hours (BMW specialty tools required)