A rental company manager in Istanbul was evaluating why one of his Doosan DX300LC excavators was being returned by customers with more complaints than any other machine in the fleet. The complaints varied — “cab feels rough,” “feels like something’s loose,” “noisy at low RPM.” The manager assumed the machine had a mechanical defect and sent it for a full service evaluation. The service team found nothing wrong mechanically. Then a used-equipment appraiser visiting the yard did a quick Shore A test on the engine mounts: the values came back at Shore A 22-26 — against a specification of 52-60. The mounts had degraded completely. At Shore A 22, the engine was effectively floating on worn-out rubber, transmitting its full vibration energy directly into the cab and upper structure. Four new engine mounts transformed the machine. The next rental customer called to compliment the machine’s quality. Rubber cost: $280. Recovered fleet reputation: significant.
Doosan Infracore (now HD Hyundai Infracore, operating construction equipment under the Doosan and Bobcat brands) produces a range of excavators from compact mini-excavators through large mining-class machines. The DX-series covers the mainstream excavator range; Bobcat E-series covers compact and mini-excavator classes. This guide covers rubber parts for DX-series excavators from DX140 to DX490, with notes on Bobcat compact models.
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Engine Isolation Mounts for Doosan DX Series
Doosan DX-series excavators use Doosan’s own DL-series diesel engines across the main size range. Engine mount specifications vary significantly from compact to large-class machines.
DX140LC/DX160LC Engine Mounts
Doosan DX140 (Doosan DL06 engine, 85 kW):
– Mount quantity: 4-point
– Shore A: 48-54
– Compound: NR/SBR standard blend
– Temperature: -30°C to +100°C
DX140 is common in utility construction, drainage work, and urban demolition. Engine mount inspection at 3,000-hour intervals for standard duty.
DX225LC/DX235LCR Engine Mounts
The DX225LC is Doosan’s flagship mid-class excavator — equivalent in role to CAT 320, Komatsu PC200, and Volvo EC220:
– Engine: Doosan DL06K (128 kW)
– Shore A: 50-58
– Compound: Heat-stabilized NR for Middle East and Central Asian deployment (Doosan has large market presence in both)
– Load per mount: 220-280 kg
– Inspection interval: 3,000 hours standard; 2,000 hours in quarry or demolition duty
The Istanbul case above occurred on a DX300 but the failure mode — gradual rubber hardening from heat cycling followed by compound breakdown — applies equally to DX225 and any other Doosan model in extended service without mount inspection.
DX300LC/DX340LC Engine Mounts
DX300LC (Doosan DL08 engine, 170 kW):
– Shore A: 52-60
– Compound: NR with heat stabilization
– Load per mount: 320-400 kg
DX340 is commonly used in rock excavation and difficult ground conditions where engine loading is high and mount heat exposure is increased by the high duty cycle.
DX420LC/DX490LC Engine Mounts — Large Class
DX490LC (Doosan DL08 engine, 270 kW) — Doosan’s largest standard production excavator:
– Shore A: 55-65
– Compound: High-temperature NR
– Mount quantity: 6-point system on DX490
– Load per mount: 450-540 kg
– Note: DX490 is used in large quarry and mining application — very high duty cycle demands increased inspection frequency at 2,000-hour intervals
For detailed comparison of excavator engine mount specifications across CAT, Komatsu, Volvo, and other brands, see our excavator engine mounts guide.
Cab Isolation Mounts for Doosan DX Excavators
Doosan’s DX-series ROPS cabs use 4-point isolation on DX140-DX300 and 6-point on DX420/DX490. Doosan has invested significantly in cab comfort with the DX-series, including air-cushioned seats and cab isolation — which means cab mount degradation is more noticeable as the machine ages because the baseline quality is high.
DX225LC Cab Mount System
- Mount quantity: 4-point
- Front mounts: Shore A 38-46
- Rear mounts: Shore A 45-53
- Temperature: -40°C to +110°C
- Compound: NR
DX300/DX490 Cab Mount System
Larger DX models use 6-point isolation:
– Front mounts: Shore A 36-44 (softer on larger models — heavy cabs require softer mounts to achieve same isolation frequency)
– Rear mounts: Shore A 44-52
– Upper rear mounts: Shore A 48-56
– Temperature: -40°C to +110°C with heat-stabilized compound for >40°C ambient operation
Vibration isolation effectiveness degrades as rubber hardens — the Doosan DX-series cab mount system is tuned for a specific isolation frequency at design Shore A. Mounts that have hardened to 20-30% above design Shore A reduce isolation frequency (worse for occupant) while softened mounts (from heat degradation or oil contamination) reduce load capacity.
Bobcat E-Series Compact Excavator Rubber Parts
Bobcat compact excavators (E10 through E165) use the same rubber maintenance approach as full-size excavators at reduced scale. Key rubber components for Bobcat compact excavators:
Bobcat Engine Mounts (Mini Excavators)
Bobcat E10-E50 (Kubota diesel, 7-30 kW):
– Mount quantity: 4-point
– Shore A: 42-50 (softer compound appropriate for small, lower-vibration engine)
– Compound: Standard NR/SBR blend
– Replacement interval: 2,500-3,500 hours (mini-excavators work in high-cycle urban trenching)
Bobcat E85-E165 (larger engine range):
– Shore A: 48-56
– Compound: NR or NR/SBR depending on operating temperature
Bobcat Cab Isolation (E-Series)
Bobcat E-series enclosed cab models use 4-point isolation:
– Shore A: 35-45 (standard range)
– Temperature: Standard -30°C to +100°C range
Bobcat Hydraulic System Seals
Bobcat compact excavators use the same hydraulic seal architecture as full-size excavators at reduced bore sizes. For Bobcat E85-E165:
– Boom cylinder seal kit: NBR rod seals, polyurethane piston seals
– Bucket cylinder: Same seal specification as boom at smaller bore diameter
– Track motor seals: NBR hydraulic motor shaft seals
Replacement interval for compact excavator hydraulic seals: 3,500-5,000 hours in standard construction duty. Higher frequency for demolition or trench work in contaminated ground water.
Hydraulic Seals for DX-Series Excavators
Boom and Arm Cylinder Seals
Doosan DX-series hydraulic cylinders use a standard NBR and polyurethane seal package:
– Rod seal: Polyurethane primary seal with NBR backup (DX225-DX490)
– Piston seal: Double-acting NBR (standard) or polyurethane (high-pressure applications)
– Guide/wear ring: PTFE-composite for low friction
– Wiper seal: NBR single-lip wiper
For detailed guidance on hydraulic excavator seal specifications, see our hydraulic excavator rubber seals guide.
Operating pressure: 350-400 bar in DX300-DX490 boom circuits. High-pressure polyurethane seals are recommended for these larger models over standard NBR.
Undercarriage Duo-Cone O-Rings
Doosan DX-series final drives, track rollers, and carrier rollers use Duo-Cone floating face seal assemblies. Duo-Cone O-ring specifications:
– Compound: NR
– Shore A: 68-72 (tight tolerance for correct face seal preload)
– Dimensional accuracy: ±0.1 mm critical
Doosan’s DICP (Doosan Infracore Constant Pressure) hydraulic system maintains track tension through the central track tension cylinder — this cylinder also uses NBR seals and must be serviced when track tension is adjusted.
Quality and Replacement Intervals
| Component | DX140/DX160 | DX225/DX235 | DX300/DX340 | DX490 |
|---|---|---|---|---|
| Engine mounts | 4,000 hrs | 3,500 hrs | 3,000 hrs | 2,500 hrs |
| Cab mounts | 3,500 hrs | 3,000 hrs | 3,000 hrs | 2,500 hrs |
| Boom cylinder seals | 5,000 hrs | 4,000 hrs | 4,000 hrs | 3,500 hrs |
| Duo-Cone O-rings | 7,000 hrs | 6,500 hrs | 6,000 hrs | 5,500 hrs |
| Track motor seals | Annual | Annual | Annual | Annual |
Quarry and demolition duty: reduce all intervals by 25-35%.
Conclusion
Doosan DX-series and Bobcat excavators cover one of the widest size ranges of any manufacturer — from 1-tonne Bobcat mini-excavators to 50-tonne DX490 machines. Across this range, the rubber maintenance principles are consistent: inspect engine mounts and cab mounts at 2,000-3,000 hours, check Duo-Cone O-ring condition at each major service, and replace hydraulic cylinder seals proactively before bypass leakage develops.
The Istanbul DX300 case makes the key point: gradual rubber degradation is invisible until a Shore A test or operator complaint reveals it. Condition monitoring with simple Shore A testing at each 1,000-hour service prevents degraded rubber from becoming a fleet reputation problem.
Babacan Group manufactures Doosan and Bobcat rubber parts under ISO 9001:2015 certification, covering DX140 through DX490 and Bobcat E-series. Browse our rubber parts catalog or request a technical quote with your Doosan or Bobcat model.