##EVC HolyGrail Solution – Validated Results
Front Drive and Rear eDrive Unit Failure – Mercedes EQC – HolyGrail EVC eDrive KIT and repair procedure is here!
The Root Cause: SiC Mechanical Seal Failure
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 — including Audi, VW and Mercedes — have complicated reliability by introducing an unproven and fundamentally flawed SiC seal technology. Furthermore, this failure repeats across all iterations without exception.
The best course of action is a preventive upgrade to the EVC HolyGrail solution before the seal fails and before coolant destroys the stator winding and other components. To date, we have successfully validated 4 vehicles with the HolyGrail PTFE Nylon solution combined with a stainless steel nano-coated rotor sleeve. This solution is designed to surpass 200,000 km without leakage — and we are targeting at least 500,000 km, a standard we already set for the Tesla LDU, road-validated to 960,000 km by Hansjörg in his Model S P90.
Dear OEMs — it is time to permanently abandon SiC mechanical seals. This component is clearly a sustainability killer, systematically destroying EQ and eTron vehicles across the fleet.
Drive Unit Condition & Damage Assessment
On the EQC, most bearings are commercially available, with the exception of one specific type. Moreover, the overall layout of this drive unit is very similar to the EQV motor, though not identical.
In the photos, you can clearly see severe wear of the sealing surface extending all the way down to the housing — a condition that caused vibration and coolant leakage. As a result, the stator windings show initial mechanical damage, while the bearings are completely compromised: burnt and contaminated with oil. Notably, coolant did not directly affect the bearings in this case — the bearing damage was caused by oil contamination and mechanical vibration alone.
OEM vs EVC Repair Cost Comparison
| Cost (ex. labor) | |
|---|---|
| Remanufactured OEM unit | ~€2,500 + VAT |
| New / newer OEM revision | ~€5,200 + VAT |
| EVC repair/reman (longer-lasting solution) | €2,500–€3,800 + VAT |
In contrast to OEM replacement, the EVC solution uses superior materials and therefore provides a longer design life at a lower or equivalent cost.
Technical Specifications & Compatible Part Numbers
- Motor manufacturer: ZF
- Seal supplier: KACO (likely) — not commercially available for purchase
- Failure mileage: 20,000–120,000 km
- OEM part numbers: A2933406800, A2933405000, A2933406300, A2933408400, A2933409300, A2933409600, A2933403700, A2933405100, A2933406400, A2933408500, A2933409400, A2933409700
If you are buying EQC, it is mandatory to make preventive eDrive remanfucturing (REMAN)
EVC HolyGrail Repair Kits — For Certified EV Clinic Franchises
