Main relief valve (MRV) 25/222659 JCB 3CX/4CX, genuine

25/222659

Brand
JCB
Article
25/222659
Machine system
Hydraulic system
Part type
Relief valve
Machine brand
JCB
Manufacturing type
Original
Compatibility
JCB 3CX, 4CX
All the features

In stock

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Main relief valve (MRV) 25/222659 is a genuine JCB part for the JCB 3CX and 4CX backhoe loaders. The card also lists 25/618901, 25/619001, 334/Y2444.

A relief valve limits circuit pressure to its set value: when pressure exceeds it, the valve opens and sends the excess oil to tank. The main relief valve (MRV) in the valve block limits pump pressure, while the auxiliary relief valves (ARVs) in the cylinder lines limit pressure spikes from shocks and external loads on the arm. A valve with a dropped setting or a leak causes loss of force and creep under load, and a stuck one can burst a hose and damage the pump. The set pressure is given in the product name. The cartridge is supplied new with a factory setting. The set pressure is chosen for the circuit and cylinder it protects, and valves with different settings may sit on the same valve block. The setting may be marked on the valve body. The valve is made of steel.

Specifications

Part number	25/222659
Cross / alternative numbers	25/618901, 25/619001, 334/Y2444
Manufacturer	JCB
Production type	Original
Part type	Relief valve
System / group	Hydraulic system
Machine make	JCB

Compatibility

The catalogue also has the aftermarket version of this part. Other parts are in Hydraulic valves.

Fitting

After fitting, check the joint for leaks; if the setting differs, adjust only to the service manual figure.

Specifications

Machine system
Hydraulic system
Part type
Relief valve
Machine brand
JCB
Manufacturing type
Original
Compatibility
JCB 3CX, 4CX

Questions: 0

No questions about this product.

JCB 3CX / 4CX 07/10/2026 49

JCB 3CX and 4CX hydraulic circuit diagrams by build year, with component keys

There is no single hydraulic circuit for the JCB 3CX and 4CX backhoe loader: it depends on the build year and the pump type. Section E of the JCB service manual (publication 9803/3290-14) gives separate circuits for the gear pump 3CX built before and after September 2007, for the variable flow 4CX (7-spool and 6-spool), and for the 3C-14 (214e) and 3C machines. Below you will find the circuits themselves, the component keys and some notes on tracing the oil flow through a circuit.

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JCB 3CX / 4CX Hydraulic Pressure: Settings, Pressure Testing and Causes of Low Pressure

On JCB 3CX and 4CX backhoe loaders with a gear pump, the working pressure of the hydraulic system is limited by the main relief valve in the loader valve: 236–241 bar on machines up to serial number 964124 and 248–252 bar on machines from serial number 964125 (standard and high-pressure hydraulics). It is checked with a 0–400 bar pressure gauge connected to the loader valve test point, with the engine at 1500 rev/min and the oil warmed to 50 °C. Below are the settings, the test procedure and the reasons why pressure drops, taken from the JCB service manual (Section E).

JCB 3CX / 4CX 07/10/2026 18

JCB 3CX / 4CX Hydraulics: Circuit Diagrams, Pumps and Relief Valve Pressures

Section E of the JCB service manual (publication 9803/3290-14) deals with the hydraulic system of the JCB 3C, 3CX and 4CX backhoe loaders. It brings together technical data for the pumps and valve blocks, hydraulic circuits for machines of different build years, valve operation, fault finding tables, and the procedures for pressure testing and for overhauling the pump, valves and rams. The section PDF runs to 302 pages.