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angled top view of silver union nut socket showing U-shaped open end and cylindrical driver endangled view of union nut socket highlighting square driver recess and raised engagement tabside profile of silver union nut socket showing flat bridge and U-shaped open pocket between cylindrical ends

Union Nut Socket, 3/8-Inch Drive, 17x78mm, VAG TDI Diesel Injector Application

Specialized socket for high-pressure diesel injector unions on VAG TDI engines; 3/8-inch drive, precision-machined for reliable removal without damage.

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Description

Union Nut Socket, 3/8-Inch Drive, 17x78mm, VAG TDI Diesel Injector Application

Brief Overview

This is a purpose-built socket for disconnecting high-pressure fuel injector unions on VAG group TDI diesel engines. Unlike general-purpose sockets, this tool features an open-end design with internal engagement geometry that grips the union nut securely without stripping or cam-out—critical when working with precision fuel systems where damage means costly repairs.

If your shop handles VW, Audi, Seat, or Skoda TDI service work, this socket is essential inventory. It pairs well with specialized fuel injector removal tools designed for similar high-pressure applications.

Key Features

  • 3/8-inch square drive – Compatible with standard ratchets and torque wrenches
  • 17x78mm union nut engagement – Precisely sized for VAG TDI fuel lines
  • Open-end design with internal ribs – Prevents nut slippage and damage to soft brass fittings
  • Single-piece machined construction – No moving parts means durability and zero maintenance
  • Matte silver finish – Corrosion-resistant plating for workshop longevity
  • Compact profile – Fits in tight engine bay spaces typical of modern turbodiesels

Technical Specifications

Specification Detail
Drive Size 3/8 inch
Socket Engagement 17x78 mm
Design Open-end union nut socket
Material Machined metal with protective plating
Finish Silver/matte (corrosion-resistant)
Construction Single-piece, stamped/machined

VAG Application Coverage

Volkswagen:

  • Polo (6R)
  • Golf (1K, 5K, AJ)
  • Passat (3C)

Audi:

  • A1 (8X), A3 (8P), A4 (8K), A6 (4F), A8 (4E), A8 2003+

Seat:

  • Ibiza (6J), Leon (1P)

Skoda:

  • Fabia II (54), Octavia II (1Z)

Engine Coverage:

  • 8-cylinder TDI Common Rail 4.0 4V
  • 6-cylinder TDI Common Rail 3.0 4V

Why Resellers Profit From This Tool

  • Narrow, high-value niche: Diesel TDI service shops need this specific socket—not a general alternative
  • Repeat orders: Mechanics who service VAG TDI fleets will stock multiple units
  • Higher margin category: Specialized sockets command better margins than basic metric sets
  • Bundling opportunity: Pair with fuel line connectors, injector seals, or fuel filters for larger orders
  • Reduced damage liability: Proper union nut removal means fewer comebacks and better shop reputation

Why Mechanics Choose This Socket

High-pressure fuel systems demand precision tools. Generic sockets risk stripping the soft brass union nuts—a mistake that escalates into fuel leaks, TDI performance issues, or complete fuel rail replacement. This socket's engineered engagement geometry grips cleanly without deformation. For shops handling VAG diesel warranty work, using the correct tool is not optional.

Business Advantage Summary

Stock this socket if you service:

  • Fleet VW/Audi/Seat/Skoda TDI vehicles
  • Diesel fuel injection specialists
  • OEM warranty repair centers

Minimal footprint, specialized application, strong margin potential. This is the type of tool that builds distributor loyalty when shops realize you understand their niche.