# 1029 Dunbier H3341 Mackay Coupling Master Cylinder and Hand Brake Assembly | Marine Trailer Part

🔧 Product Description

  

Dunbier Hydraulic Override-Coupling Master Cylinder and Handbrake Assembly - Part Number: 1029

  

A complete replacement hydraulic master-cylinder and parking-brake lever assembly for the Dunbier 1030 override coupling. The assembly converts drawbar compression into hydraulic brake pressure while also providing a manual handbrake function when the trailer is parked.

  

⚙️ Key Features

  

• Combined hydraulic master cylinder and handbrake assembly

• Replacement unit for the Dunbier hydraulic override coupling

• Includes reservoir, piston mechanism and operating lever as supplied

• Restores service braking and parking-brake operation

• Designed for marine-trailer hydraulic disc-brake systems

  

📏 Specifications

  

• Application: Dunbier 1030 hydraulic override coupling

• Mackay reference: H3341

• Brake fluid type must match the complete existing hydraulic system

• Outlet fitting and pushrod geometry must match the original assembly

  

🔄 Cross Reference & Related Parts

  

• Dunbier: 1029

• Mackay: H3341

• Complete hydraulic coupling: Dunbier 1030

• Reverse stop and pin: Dunbier 1042C or 1046

• Comparable master cylinders are not interchangeable unless bore, stroke, fittings and mounting match

  

🚤 Trailer Compatibility & Application

  

• Suitable for trailers fitted with the Dunbier 1030 hydraulic override coupling

• Compatible brake calipers and hydraulic lines must be in serviceable condition

• Not for mechanical-cable override systems

  

🔌 Function

  

Generates hydraulic pressure when the coupling compresses during deceleration and applies the parking brake through the integrated handbrake lever.

  

Common signs of wear or replacement:

  

• Brake fluid leaks around the piston, cap or outlet

• Soft or ineffective trailer braking

• Master-cylinder piston sticks or does not return

• Handbrake lever will not hold adjustment

• Contaminated, dark or water-affected brake fluid

  

🛠️ Installation & Safety

  

• Brake hydraulic work should be carried out by a competent trailer-brake technician

• Flush contaminated lines and inspect calipers before fitting the new cylinder

• Use only the specified brake fluid and bleed all air from the system

• Adjust the coupling pushrod and handbrake according to the coupling instructions

• Test braking at low speed before returning the trailer to road use

  

📦 Condition

  

• Brand new Dunbier Marine Products trailer component

• Supplied as one master-cylinder and handbrake assembly

• Supplied in original or equivalent packaging

## Details

- **Price:** 124.0 AUD
- **Vendor:** Dunbier
- **Tags:** Dunbier Boat Trailers | Marine Trailer Parts & Accessories

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| Default Title | 124.00 AUD | In stock |

## Images

- 1029 Dunbier H3341 Mackay Coupling Master Cylinder and Hand Brake Assembly | Marine Trailer Part

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> Source: [Sawley's Auto and Marine](https://www.sawleysautoandmarine.com.au/products/1029-dunbier-coupling-master-cylinder-hand-brake-assembly-mackay-h3341)
> Updated: 2026-08-05