# 1954 Dunbier H3090 Mackay Replacement Piston O-Ring and Boot Hydraulic Caliper # 1956 | Marine Trailer Part

🔧 Product Description

  

Dunbier Hydraulic-Caliper Piston O-Ring and Dust-Boot Kit - Part Number: 1954

  

A replacement hydraulic piston seal and protective rubber boot for the Dunbier 1956 AL-KO/Meher-style caliper. The pressure seal contains brake fluid inside the caliper bore, while the external boot helps exclude water, road dirt and salt from the piston surface.

  

⚙️ Key Features

  

• Matched hydraulic piston O-ring and dust boot

• Designed for Dunbier 1956 caliper rebuilds

• Brake-fluid-resistant elastomer construction

• Helps prevent fluid leakage and piston corrosion

• Essential replacement whenever the piston is removed

  

📏 Specifications

  

• Kit contents: Hydraulic piston seal/O-ring and protective dust boot

• Application: Dunbier 1956 / Mackay H3010 hydraulic caliper

• Brake-fluid compatibility must match the installed system

  

🔄 Cross Reference & Related Parts

  

• Dunbier: 1954

• Mackay: H3090

• Replacement piston: Dunbier 1953 / Mackay H3080

• Slide-pin kit: Dunbier 1955 / Mackay H3084

• Complete caliper: Dunbier 1956 / Mackay H3010

  

🚤 Trailer Compatibility & Application

  

• Suits the floating hydraulic caliper fitted to Dunbier AL-KO and Meher brake axles

• Confirm the seal profile against the removed parts

• Not suitable for mechanical calipers

  

🔌 Function

  

Seals hydraulic pressure around the piston and protects the exposed piston-to-bore area from contamination.

  

Common signs of wear or replacement:

  

• Brake fluid leaks from the caliper

• Boot is split, loose, swollen or missing

• Piston does not retract smoothly

• Water or corrosion is visible behind the boot

• Seal has hardened or become distorted

  

🛠️ Installation & Safety

  

• Clean the caliper with brake-safe products only

• Do not scratch the seal groove during removal

• Install the seal and boot without twisting

• Use only compatible brake fluid or approved assembly lubricant

• Bleed and pressure-test the brake circuit after reassembly

  

📦 Condition

  

• Brand new Dunbier Marine Products trailer component

• Supplied as one piston O-ring and dust-boot repair kit

• Supplied in original or equivalent packaging

## Details

- **Price:** 29.5 AUD
- **Vendor:** Dunbier
- **Tags:** Dunbier Boat Trailers | Marine Trailer Parts & Accessories

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| Default Title | 29.50 AUD | In stock |

## Images

- 1954 Dunbier H3090 Mackay Replacement Piston O-Ring and Boot Hydraulic Caliper # 1956 | Marine Trailer Part
- 1954 Dunbier H3090 Mackay Replacement Piston O-Ring and Boot Hydraulic Caliper # 1956 | Marine Trailer Part
- 1954 Dunbier H3090 Mackay Replacement Piston O-Ring and Boot Hydraulic Caliper # 1956 | Marine Trailer Part

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> Source: [Sawley's Auto and Marine](https://www.sawleysautoandmarine.com.au/products/1954-dunbier-replacement-piston-o-ring-boot-hyd-calliper-1956-mackay-h3090)
> Updated: 2026-08-05