Stop the Drip: A Step-by-Step Guide to Fixing a Hydraulic Hose Leak

It's not just a messy inconvenience when a hydraulic hose is leaking; it's a serious safety hazard, a cause for inefficiency within the system, and a sign of an impending risk to your machinery. Whether it is just a slow leak or a spraying high-pressure leak, the important thing is to address it promptly, or your reliability and efficiency will suffer.

This guide will help you identify various types of leaks and safe procedures pinpointing the most common sources of failure: the fittings and the hose body.

Safety First: Before You Start

Hydraulic systems operate at very high pressure. Do not attempt to inspect or repair a leak while under pressure.

De-energize the unit: Turn the equipment off and lock out the energized circuit.

Depressurize the system: Cycle the controls or slowly open the relief valve to release and relieve the pressure within the hydraulic lines and actuators.

Use PPE (personal protective equipment): Always wear safety glasses (or a face shield) and proper gloves. High-pressure fluid injection injuries are a serious matter, and can be fatal. Never use your hands to check a leak!

Dissipate heat: Allow time for the system and fluid to cool before touching the components.

Step 1: Identifying the Leak Type and Location

Leaks typically originate from three locations, and how it is fixed will depend on where the fluid is leaking from

1. Leak at the Fitting / Connecting Point

This is the most common leak location. Fluid is leaking from the connection point of the hose end to the port or adapter.

Cause: Improperly torqued, damaged/missing O-ring/seal, or a loose locknut.

Fix: Generally requires tightening or replacing the seal. 

2. Leak at the Crimp Collar (Hose Fitting Transition Point)

This refers to a metal crimp sleeve holding the hose end to the flexible hose.

Cause: Improper crimp specifications from assembly (too tight or too loose), or the hose failing due to pressure cycling or age.

Fix: Requires full hose replacement.

3. Leak on the Hose Body (Mid-Section)

The fluid is either spraying or weeping from the rubber or thermoplastic portion of the hose.

Cause: Abrasion, cutting, kinking, or failure from excessive wear causing the outer cover and internal reinforcement layers to fail.

Fix: Requires full hose replacement.

Step 2: Repair Procedure (Focus on Fitting's position)

If the leak appears at the connection point of a hose and fitting, and the hose and fitting are in good condition, take the appropriate action for the type of fitting.

A. O-Ring Boss (ORB) and Face Seal (ORFS) Fitting

These fittings use a profiled O-ring to create a seal at the connection (they leak primarily due to damage to the O-ring or loose fittings).

Loosen and Check: Carefully remove the torque of the fitting or tube nut.

Remove and replace the O-Ring: Remove the damaged O-Ring from the fitting groove and check the sealing surface for scratches or damage.

Install new O-Ring: Install a new O-Ring of the proper size (O-rings are made of Nitrile or Viton and should be lubricated with hydraulic fluid compatible to seal the O-ring properly).

Reassemble and torque: Install hand-tight and torque the fitting to the vendor's requirements (you should never over-torque a fitting as this will crush the O-ring, resulting in either a leak or a lower pressure seal).

B. Disassembling and Re-sealing Tapered Pipe Thread (NPT/NPTF) Fittings

These threads work by wedging together and also have sealant (from the previous post).

Disassemble: Locate the male fitting and unit and remove this completely from the female port. 

Clean Threads: Clean both the male and female threads well, with any old sealant, tape or debris removed.

Apply New Sealant: Use a good quality liquid anaerobic thread sealant rated for high-pressure hydraulics and apply to the threads of the fitting. Leave the first 1-2 threads bare of sealant when applying to prevent contaminants from entering the system during installation. 

Reassemble and Tighten: Reinstall the fitting and tighten to the recommended position or torque. With NPT fittings, ample snug and tight to prevent leaks is essential, but try to avoid over-torquing as it could crack the port.

Step 3: When to Replace the Whole Hose

If the leak is from the crimp collar or some other point on the hose body, do not attempt to make a temporary repair. A failed hose indicates that internal structural damage has occurred, and the hose must be replaced right now.

Watch for: Bubbling on the outer cover, blisters, excessive abrasion, kinking, or visible wire reinforcement.

Steps to Replace:

Measure the total length and identify the end fitting types (JIC, ORB, Flange, etc.), position/orientation (straight, 90°, etc.), and hose diameter (ID).

Have a professional hose assembly business construct an exact replacement to the original equipment manufacturer's (OEM) rated working pressure and specifications.

Re-install the hose without changing the routing method, and secure the hose using the appropriate clamps for proper support, to avoid potential and future abrasion.

Step 4: Test and Inspect

After the repair or replacement has been completed:

Refill: Refill the hydraulic reservoir with the clean compatible fluid.

Pressurize: Switch on the system and pressurize slowly up to normal working pressure while continuing to check the point of repair.

Final Inspection: Visually and audibly check for signs of leakage. If it continues to leak, shut off the system and repeat the first two steps.