Merlo DBM 2500 EV and DBM 3500 EV Hydraulic System Service Manual [PDF] ENG

This PDF service manual provides detailed technical information for diagnosing, testing and servicing the hydraulic system of the Merlo DBM 2500 EV and DBM 3500 EV.

It is intended for qualified mechanics, service workshops and experienced technicians familiar with hydraulic, mechanical and electrical systems. The manual covers specialist maintenance and diagnostic procedures that are not normally included in the standard operation and maintenance handbook.

The document includes detailed hydraulic diagrams showing how the pumps, valves, filters, cylinders, motors and control systems are connected. It also provides pressure-test values, valve-adjustment information and troubleshooting charts to help locate hydraulic faults.

The manual includes

• Complete hydraulic system diagram;
• Hydraulic component identification;
• Steering and main distributor system;
• Steering pump and priority valve;
• Power-steering system;
• Steering control from the drum side;
• Main directional control valve and joystick controls;
• Hydraulic pressure testing and adjustment;
• Steering and oil-supply troubleshooting;
• Mixing-drum rotation circuit;
• Drum rotation pump and hydraulic motor;
• Drum rotation pressure testing;
• Loading shovel lifting and rotation system;
• Shovel safety and control valves;
• Drum lifting and side-rotation circuit;
• Discharge chute lifting system;
• Water-pump hydraulic drive;
• Filters, solenoid valves and oil-flow regulators;
• Metric tightening-torque specifications;
• Information about sealants, thread-locking products and assembly lubricants.

Hydraulic system diagram

The main hydraulic diagram identifies the principal components, including:

• Suction and return filters;
• Steering and distributor pump;
• Priority and steering valves;
• Power-steering cylinders;
• Main directional control valve;
• Drum rotation pump and motor;
• Shovel lifting and rotation cylinders;
• Drum lifting and side-rotation cylinders;
• Chute lifting cylinder;
• Water-pump hydraulic motor;
• Solenoid valves and oil-flow regulator.

Steering and distributor system

This section explains the complete steering and hydraulic oil-supply circuit, including the pump, load-sensing priority valve, power-steering unit and steering control valves.

It includes information about:

• Steering pump specifications;
• Priority oil supply to the steering system;
• Power-steering pressure adjustment;
• Steering from the drum-side driving position;
• Main directional control valve connections;
• Hydraulic pressure testing;
• Steering and supply-system troubleshooting.

The steering system operates using a load-sensing priority valve, with a maximum steering pressure of approximately 175 bar.

The main hydraulic system pressure is adjusted using the relief valve, with a specified pressure of 180 bar under the stated test conditions.

Mixing-drum rotation system

The drum rotation section covers:

• Variable-delivery drum rotation pump;
• Hydraulic drum motor;
• Clockwise and counter-clockwise rotation solenoids;
• Pressure-relief valves;
• Charge-pump relief valve;
• Drum motor drain filter;
• Return filter;
• Pressure testing;
• Drum rotation fault diagnosis.

The drum rotation pressure test specifies a system pressure of approximately 210 bar.

The troubleshooting section helps diagnose conditions such as:

• Drum not rotating in either direction;
• Drum operating in only one direction;
• Slow drum rotation;
• Clogged filters or restrictors;
• Defective pressure-relief valves;
• Faulty solenoid valves;
• Insufficient oil level or suction leaks.

Loading shovel system

The shovel section explains the hydraulic circuit for lifting and rotating the loading bucket.

It includes:

• Shovel lifting cylinders;
• Shovel rotation cylinders;
• Cam-operated diverter valve;
• Single-acting safety valve;
• Automatic bucket rotation when the booms rise above the horizontal position;
• Fault diagnosis for leaking cylinders, incorrect movement and slow operation.

Drum lifting and side rotation

This section covers the hydraulic cylinders and controls responsible for:

• Raising and lowering the mixing drum;
• Rotating the drum assembly sideways;
• Controlling system pressure through the main relief valve.

Discharge chute lifting system

The manual identifies the chute lifting cylinder, main distributor connections and hydraulic pressure-control arrangement used to raise and lower the discharge chute.

Water-pump system

The water-pump section covers the hydraulic motor and compensated flow regulator used to operate the machine’s water pump.

The regulator maintains a constant oil flow to the water-pump motor despite changes in hydraulic pressure, while excess oil is returned to the tank.

Product information

Manufacturer: Merlo
Applicable models: DBM 2500 EV and DBM 3500 EV
System covered: Main hydraulic system
Document type: Workshop Service Manual
Manual reference: DBM-OLEO.01
Application: From SAV 741511 onwards
Language: English
Format: Digital PDF file
Number of pages: 43 pages

Important information before purchase

Please check your machine model and SAV number before purchasing.

This is a specialised hydraulic system service manual. It covers the steering, main distributor, drum, shovel, chute and water-pump hydraulic circuits. It is not an operator’s handbook, spare parts catalogue or complete workshop manual for every machine system.

The procedures are intended for qualified technicians with suitable hydraulic pressure-testing equipment and workshop experience.