Front Drive Unit Failure – Mercedes EQC
We are once again seeing the same repeating failure pattern on ZF asynchronous induction motors: coolant intrusion through the SiC mechanical seal. Although induction motors are, by design, more durable and more sustainable than PMSM units (in terms of serviceability and long-term stability), several OEMs (Audi, VW, Mercedes) have complicated reliability by introducing an unproven and fundamentally flawed SiC seal technology. This failure repeats across all iterations.
Dear OEMs – it is time to abandon SiC mechanical seals permanently.
On the EQC, most bearings are commercially available except for one specific type. The overall layout of this drive unit is very similar to the EQV motor, though not identical.
In the photo you can clearly see severe wear of the sealing surface all the way down to the housing, which caused vibration and coolant leakage. The stator windings show initial mechanical damage, while the bearings are completely compromised – burnt and contaminated with oil. (Coolant did not directly affect the bearings in this case.)
OEM pricing:
•Remanufactured unit: ~€2,500 + VAT
•New or newer revision: ~€4,200 + VAT (labor not included)
Unlike the Tesla LDU, this motor cannot be permanently repaired due to the weak design of the sealing area, where it is not possible to apply our graphite-type long-life seal with rotor machining.
(However, if someone has a faulty motor they are willing to donate for parts, we could attempt to engineer a prototype solution.)
Technical details:
•Part number: A2933406800
•OEM pricing: €2,500–€4,200
•EVC repair/reman price: €2,500–€3,800
•Motor manufacturer: ZF
•Seal supplier: KACO? (likely) not commercialy available for purchase
Mileage: 120,000km