# H3074 Mackay 1880 Dunbier Hydraulic Union Connection (Override Coupling & Caliper) | Marine Trailer Part

🔧 Product Description

  

Mackay Hydraulic Brake-Line Union Connector - Part Number: H3074

  

A brass hydraulic connector for joining compatible trailer brake lines to master cylinders and calipers. The fitting matches common original trailer brake-line connections.

  

⚙️ Key Features

  

• Brass hydraulic fitting

• Connects brake line to master cylinder or caliper

• Corrosion-resistant material

• Suitable for common Mackay/Dunbier hydraulic systems

• Reusable only when threads and seats remain undamaged

  

📏 Specifications

  

• Application: Override coupling master cylinder and hydraulic calipers

• Dunbier reference: 1880

• Thread and sealing-seat style must match both components

  

🔄 Cross Reference & Related Parts

  

• Mackay: H3074

• Dunbier: 1880

• Copper gasket: H3073 / Dunbier 1881

• Three-way tee: H3075 / Dunbier 1860

  

🚤 Trailer Compatibility & Application

  

• Suitable for common 3/16-inch trailer hydraulic brake plumbing

• Do not mix flare, inverted-flare, banjo or tapered-thread fittings

  

🔌 Function

  

Provides a pressure-tight transition between the brake hose/line and the hydraulic component.

  

Common signs of wear or replacement:

  

• Brake fluid leaks

• Threads are crossed or stripped

• Seat is scored

• Hex is rounded

• Corrosion prevents removal

  

🛠️ Installation & Safety

  

• Identify the thread and seat before fitting

• Start by hand

• Use the required copper washer or flare seal

• Do not overtighten brass fittings

• Bleed and pressure-test after installation

  

📦 Condition

  

• Brand new Mackay trailer component

• Supplied as one brass hydraulic union connector

• Supplied in original or equivalent packaging

## Details

- **Price:** 7.0 AUD
- **Vendor:** Mackay
- **Tags:** Mackay Boat Trailers | Marine Trailer Parts & Accessories

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| Default Title | 7.00 AUD | In stock |

## Images

- H3074 Mackay 1880 Dunbier Hydraulic Union Connection (Override Coupling & Caliper) | Marine Trailer Part
- H3074 Mackay 1880 Dunbier Hydraulic Union Connection (Override Coupling & Caliper) | Marine Trailer Part
- H3074 Mackay 1880 Dunbier Hydraulic Union Connection (Override Coupling & Caliper) | Marine Trailer Part

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> Source: [Sawley's Auto and Marine](https://www.sawleysautoandmarine.com.au/products/h3074-mackay-hyd-union-connection-o-r-coupling-caliper-1-dunbier-1880)
> Updated: 2026-08-05