Genuine OEM 1K0721388AF - Clutch Master Cylinder

Product Overview

This Genuine OEM 1K0721388AF clutch master cylinder is the factory-specification hydraulic component that operates the clutch actuation system on Volkswagen and Audi models from 2005 to 2018. It fits the MK5 and MK6 Golf, GTI, and Rabbit; MK5 and MK6 Jetta and GLI; Beetle; Eos; 8N and 8P Audi A3; and 8N Audi TT Quattro across multiple engine options including 2.0T, 2.5 I5, 2.0 TDI diesel, and 3.2 VR6 configurations. The master cylinder converts pedal pressure into hydraulic force to disengage the clutch, making it essential for smooth gear changes and proper clutch engagement. As a Genuine OEM part, it meets factory specifications and carries the reliability expected from original equipment.

This clutch master cylinder is sold individually. Order quantity 1 per vehicle.

Symptoms of a Failing Clutch Master Cylinder

• Soft or spongy clutch pedal that gradually loses firmness over time
• Clutch pedal sinks to the floor and does not return to full height
• Difficulty engaging or disengaging gears, especially when cold
• Visible fluid leakage around the master cylinder or beneath the dash
• Clutch pedal requires excessive pressure or feels unusually hard to depress
• Intermittent clutch engagement or slipping under load

Cross Reference Numbers

This Genuine OEM 1K0721388AF is equivalent to or replaces the following part numbers: 1K0721388AF, 1K0-721-388-AF.

Vehicle Compatibility

This part fits the popular models below. For Fitment Confidence, please use the vehicle selector tool above to verify exact compatibility for your vehicle.

• Audi A3 2.0 L4 Gas (8P): 2006–2013
• Audi TT Quattro 3.2 V6 Gas (8N): 2008–2009
• Audi TT RS Quattro 2.5 L5 Gas (8J): 2012–2013
• Volkswagen Beetle 2.5 L5 Gas (A5): 2013
• Volkswagen Eos 2.0 L4 Gas (A5): 2007–2010
• Volkswagen Golf 2.5 L5 Gas (MK6): 2010–2012
• Volkswagen Golf TDI 2.0 L4 Diesel (MK6): 2011–2014
• Volkswagen Golf R 2.0 L4 Gas (MK6): 2012–2013
• Volkswagen GTI 2.0 L4 Gas (MK6): 2010–2014
• Volkswagen GTI 2.0 L4 Gas (MK7): 2015–2017
• Volkswagen Jetta 2.5 L5 Gas (MK5): 2005–2010
• Volkswagen Jetta 2.0 L4 Gas (MK5): 2006–2009
• Volkswagen Jetta 2.0 L4 Diesel (MK5): 2009–2010
• Volkswagen Jetta 2.5 L5 Gas (MK6): 2011–2014
• Volkswagen Jetta 2.0 L4 Gas (MK6): 2012–2014
• Volkswagen Jetta 2.0 L4 Diesel (MK6): 2009–2014
• Volkswagen Jetta 1.8 L4 Gas (MK6): 2014–2016
• Volkswagen Jetta 1.4 L4 Gas (MK7): 2015–2018
• Volkswagen Jetta 1.8 L4 Gas (MK7): 2015–2016
• Volkswagen Jetta 2.0 L4 Gas (MK7): 2015–2017
• Volkswagen Rabbit 2.5 L5 Gas (MK5): 2006–2009

This may also fit other applications. Please use the vehicle selector tool to verify fitment.

Often Replaced Together

For a complete clutch system service, many owners replace the following at the same time:

• Clutch slave cylinder (hydraulic actuator at the transmission)
• Clutch disc and pressure plate assembly
• Clutch hydraulic fluid (DOT 4 or DOT 5.1 per manufacturer specification)
• Clutch release bearing

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Frequently Asked Questions

How do I know if my Volkswagen Jetta or Golf needs a new clutch master cylinder?

A failing master cylinder typically produces a soft or spongy clutch pedal that gradually loses firmness, or a pedal that sinks toward the floor without returning to full height. You may also notice difficulty engaging gears or visible fluid leakage beneath the dash or around the cylinder itself. If the pedal feels normal but the clutch slips under load, the issue is more likely in the clutch disc or slave cylinder rather than the master. A professional diagnostic can confirm whether the master cylinder is the source of the problem.

Should I replace the slave cylinder and master cylinder together?

Yes. Both the master and slave cylinders work as a paired hydraulic system. If one has failed, the other is likely near the end of its service life. Replacing both at the same time ensures reliable clutch operation and prevents a second repair shortly after the first. Additionally, flush the clutch hydraulic system with fresh DOT 4 or DOT 5.1 fluid during the service to remove moisture and debris that may have accumulated.

What is involved in replacing the clutch master cylinder on an Audi A3 or Volkswagen Golf?

Replacement requires removing the driver's side dash panel to access the master cylinder mounted on the firewall behind the pedal box. The job involves disconnecting the hydraulic line, unbolting the cylinder, and installing the new unit with a fresh seal kit. Most technicians can complete the replacement in two to three hours. You will need basic hand tools, a brake line wrench to avoid rounding the hydraulic fitting, and a catch pan for residual fluid. After installation, the system must be bled of air to restore proper pedal feel.

Is this Genuine OEM part better than an aftermarket alternative?

Genuine OEM parts are manufactured to factory specifications and carry the same quality control and durability testing as the original component installed at the factory. They also typically come with a warranty and are guaranteed to fit without modification. While aftermarket options may cost less upfront, OEM parts often provide longer service life and eliminate fitment uncertainty, making them a reliable choice for critical hydraulic components like the clutch master cylinder.

What fluid should I use when bleeding the clutch system after installation?

Consult your vehicle's owner manual or service documentation for the exact fluid specification. Most Volkswagen and Audi models from this era use DOT 4 brake fluid, though some later models may specify DOT 5.1. Never mix fluid types, and always use fresh fluid from a sealed container to avoid moisture contamination. Moisture in the system reduces boiling point and can cause brake or clutch failure under hard driving.

Will a 2010 Volkswagen Golf master cylinder fit a 2014 Jetta?

While both the MK6 Golf and MK6 Jetta share the same platform and many components, the 1K0721388AF is designed for specific engine and transmission combinations across the fitment range. Before purchasing, confirm your exact year, model, engine type, and transmission using the vehicle selector tool on the product page. The part number may differ slightly between model lines or engine variants, so verification is essential to avoid an incompatible purchase.

Order Genuine OEM 1K0721388AF today. In-stock orders ship same or next business day from our U.S. warehouse, and our fitment team is one call away if you need help confirming the right part for your Volkswagen or Audi.

Note: All information on this page and in the FAQ is for general reference only. Verify fitment and consult a professional as needed. eEuroparts.com is not responsible for incorrect part selection or installation.