When you press the clutch pedal, hydraulic pressure generated by the master cylinder travels to the slave cylinder, which actuates the release bearing or fork that disengages the clutch plate from the flywheel. The slave cylinder can be mounted externally on the gearbox bellhousing, where it is accessible for inspection, or internally inside the bellhousing as a concentric slave cylinder — a design used on many modern cars that combines the slave cylinder and release bearing into one sealed unit. External slave cylinders fail gradually through seal wear, producing a weeping of clutch fluid and a pedal that gradually drops lower over repeated journeys. Concentric slave cylinders fail more dramatically when the internal seal ruptures, leaving the clutch unable to disengage and making gear changes impossible. Because the piston diameter and stroke length must match the hydraulic system's pressure ratio and the release mechanism travel precisely, the OE number is the only reliable way to guarantee correct operation. VALEO and SACHS supply the majority of original-equipment clutch hydraulics fitted across European vehicles, and FTE specialises in clutch actuation components. Replacement typically accompanies a clutch kit change, since accessing the concentric unit requires gearbox removal regardless.
The slave cylinder OE number is determined by gearbox type, clutch actuation design (external vs concentric), and the specific hydraulic circuit pressure ratio for your vehicle. Use the make, model, and engine selectors to filter the TecDoc-linked OE numbers on this page, and cross-reference the number on your existing unit or in the workshop manual. For concentric slave cylinders integrated with the release bearing, confirming the gearbox code is essential, as different ratios may share the same external appearance but have different piston diameters.
OEM slave cylinders are manufactured to the vehicle builder's specifications, typically by VALEO, SACHS, or FTE, and carry the exact OE references. Quality aftermarket equivalents from TRW or A.B.S. match the same dimensional and material standards. Budget alternatives often use lower-grade internal seals and piston coatings, which are more susceptible to fluid contamination and premature failure, particularly in concentric designs where replacement requires full gearbox removal.
For concentric slave cylinders, yes — always. They are located inside the bellhousing and require complete gearbox removal to access, so the labour cost of a separate return visit if it fails shortly after a clutch change is significant. For external slave cylinders, replacement at clutch change is best practice rather than a strict requirement, but given the low part cost relative to the access labour, most workshops recommend fitting a new one regardless of its apparent condition.
On external designs, the first sign is usually a weeping of clutch fluid from the dust boot or at the union fitting, followed by a pedal that sits lower than normal or requires pumping to achieve full disengagement. On concentric internal designs, failure is often sudden — the clutch becomes impossible to disengage and gear selection is blocked. A clutch pedal that operates normally but sinks to the floor if held steady, with no visible external leak, points to an internal slave cylinder seal failure.
Showing 100 of 5,696 Clutch slave cylinder OE numbers. Enter the OE on the main OE search to jump to any reference.
