Motor Seal Kits for Excavators: OEM-Quality Travel & Swing Motor Seal Kits for Komatsu, CAT, Hitachi & More

What Does a Motor Seal Kit Contain?

A complete hydraulic seal kit provides all the sealing components required for a full motor overhaul in a single, application-matched supply. Depending on the motor type and model, a standard motor seal kit contains:

• Shaft Seal — The primary rotary seal at the motor output shaft, preventing hydraulic fluid from migrating outward along the shaft into the gearbox oil chamber. Shaft seal failure is the most common and earliest indicator of motor seal degradation and the primary cause of hydraulic-to-gearbox oil cross-contamination.
• Piston Seals — On axial piston motor assemblies, piston seals maintain the critical pressure differential between motor high and low pressure sides, converting hydraulic flow into rotational torque. Worn piston seals reduce motor output torque and cause internal bypass heating.
• Valve Plate and Port Plate Seals — Sealing components at the motor's internal port distribution interfaces, maintaining separation between intake and discharge flow paths within the motor barrel assembly.
• O-Ring Set — A complete set of all o-rings at housing faces, end cover joints, port connections, and internal passages throughout the motor assembly.
• Brake Valve Seals — Sealing components within the integrated hydraulic brake valve assembly, maintaining brake circuit integrity for safe motor holding and controlled deceleration function.
• Back-Up Rings and Gaskets — Anti-extrusion back-up rings and flat gaskets at high-pressure housing joints and port faces where o-rings alone are insufficient for reliable sealing under full motor operating pressure.

Travel Motor Seal Kits vs Swing Motor Seal Kits

While travel and swing motors share similar internal architectures as axial piston assemblies with integrated planetary gearboxes, their seal kits are not interchangeable; each is specifically engineered for the dimensional specifications, pressure ratings, and sealing requirements of its respective motor model:

• Travel Motor Seal Kits — Engineered for the higher continuous torque and sustained pressure demands of the track drive circuit. Travel motors operate under constant directional load from machine weight and ground resistance, placing specific demands on shaft seal design and piston seal material specification. Travel motor seal failure is most commonly identified by gearbox oil discolouration from hydraulic oil ingress, or by oil weeping from the motor-to-gearbox interface face.
• Swing Motor Seal Kits — Designed for the high-frequency acceleration and deceleration cycling of the swing circuit, where the motor experiences rapid pressure reversal on every swing direction change throughout the working shift. Swing motor seal kits include brake valve sealing components critical to maintaining swing brake function and safe upper structure position holding on gradients. Swing motor seal failure typically presents first as external oil weep at the motor shaft area or pinion housing face.

Always specify whether you require a travel motor or swing motor seal kit, and confirm your machine model and motor OEM part number when contacting our parts team to ensure the dimensionally correct kit is supplied for your specific assembly.

When to Use a Motor Seal Kit vs Full Motor Replacement

Determining the correct repair strategy for a failing motor seal depends on the extent of damage at the point of discovery:

• Seal kit rebuild is appropriate when — External leakage is detected early at the shaft seal or housing face, gearbox oil inspection shows early-stage discolouration but no metallic contamination, and the motor passes a performance pressure test confirming internal piston and barrel components are within serviceable tolerance. Early intervention with a quality seal kit prevents the progressive gearbox damage that shaft seal failure causes when left unaddressed.
• Full motor replacement is required when — Gearbox oil inspection reveals heavy metallic contamination indicating bearing or gear face damage from prolonged cross-contaminated lubrication; the motor fails a performance pressure test confirming internal bypass beyond serviceable limits; or the motor has suffered a sudden catastrophic failure from severe contamination or oil starvation. In these cases, a seal kit rebuild will not restore motor performance or protect the gearbox from continued damage.
• Proactive seal kit replacement — On high-hour machines, replacing motor seals as part of a planned overhaul at the manufacturer-recommended service interval prevents the escalating repair cost that results from allowing seal failure to progress to gearbox damage. The cost differential between a proactive seal kit rebuild and a reactive complete motor assembly replacement is significant.

Motor Seal Kit Models We Supply

Imara Engineering supplies hydraulic motor seal kits for a wide range of excavator travel and swing motor models. Our most commonly supplied kits include:

• Komatsu — PC200-7, PC200-8, PC210-8, PC300-7, PC300-8, PC360-7, PC400-7, PC400-8, PC450-8
• Caterpillar (CAT) — 320C, 320D, 320D2, 323, 325C, 325D, 330C, 330D, 336D, 336E
• Hitachi — ZX200-3, ZX210-3, ZX300-3, ZX330-3, ZX450-3, ZX500-3, EX200-5, EX300-5
• Volvo — EC210B, EC240B, EC290B, EC380, EC480, EC700
• Doosan — DX225LC, DX300LC, DX380LC, DX480LC
• Kobelco — SK200-8, SK300, SK350-8, SK480, SK850
• Hyundai — R210LC-9, R290LC-9, R380LC, R480LC
• Case — CX210, CX300, CX350, CX470

Cannot find your motor model listed? Contact our parts team with your machine serial number, motor type, travel or swing, and OEM part number, and we will confirm the correct seal kit for your specific unit immediately.

Motor Seal Kit Installation: Key Requirements for a Successful Rebuild

A motor seal kit rebuild delivers reliable results only when the installation process meets the required standards of cleanliness, precision, and preparation. These are the critical steps for a successful motor seal rebuild:

1. Drain and inspect gearbox oil before disassembly — Check for metallic particles, discolouration, and hydraulic fluid contamination in the gearbox oil before committing to a seal kit rebuild. Heavy contamination indicates gearbox damage requiring complete assembly replacement rather than a seal rebuild.
2. Flush the hydraulic circuit before installation — Remove all contamination from the motor feed and drain circuit before installing the rebuilt motor to prevent immediate new seal damage from abrasive particles remaining in the circuit.
3. Inspect all shaft and bore mating surfaces — Confirm the motor output shaft journal, housing bore, and all seal groove surfaces are free of scoring and within dimensional tolerance before installing new seals. A damaged mating surface will destroy new seals immediately.
4. Use correct installation tooling — Rotary shaft seals require correct diameter installation sleeves to prevent lip damage during fitting. Never drive a shaft seal into position without the appropriate installation tool.
5. Replace gearbox oil at the same time — Always refill the final drive gearbox with fresh lubricant to the correct specification and level after any motor seal rebuild. Contaminated gearbox oil accelerates bearing and gear wear regardless of seal condition.
6. Verify brake valve function after assembly — Confirm the swing or travel brake engages and releases correctly after reassembly before returning the machine to service, particularly on gradient applications where brake failure creates an immediate safety risk.

Related Hydraulic Parts You May Need

Motor seal kit rebuild frequently connects to wider hydraulic system and drivetrain servicing. Consider sourcing these components alongside your motor seal kit:

• Travel Motors — Where motor internal damage extends beyond seal replacement, a complete travel motor assembly is the correct solution
• Swing Motors — Complete swing motor assemblies where internal damage or gearbox wear requires full assembly replacement
• Transmission Seal Kits — Replace final drive gearbox seals simultaneously with travel motor seal kit for a complete drivetrain seal overhaul
• Pump Seal Kits — Consider pump seal inspection at the same service event to address all major hydraulic circuit sealing in a single maintenance window
• O-Ring Kits — Supplement the motor seal kit with an o-ring assortment for all circuit connections and port seals disturbed during the motor rebuild