How to Check the Oil Levels on a JCB 3CX / 4CX: Hydraulics, Engine, Gearbox and Axles

How to check the hydraulic oil level on a JCB 3CX

1. Park the machine on level ground and lower the loader shovel to the ground (page 3-61).
2. If an extending dipper is fitted, retract it. Raise the excavator boom, close the dipper and crowd the bucket: this puts the rams in the position in which the manual checks the level.
3. Stop the engine and remove the key.
4. Look at the sight glass: the level should be at or above the red mark.
5. If the oil is low, remove the tank cap and top up with the recommended oil.

Cloudy oil in the sight glass means water or air has entered the system, which is harmful to the pump. The hydraulic tank cap is locked with the ignition key and contains a breather with a filter element that is renewed at the specified interval (page 3-60): turn the key anti-clockwise, and screw the cap down fully and then a further quarter turn. Allow the oil to cool below 40 °C before working on the hydraulic system (page 3-59). The total hydraulic system capacity is about 130 litres and depends on the attachments fitted; all rams should be closed when filling (page 3-12). Hydraulic oils are listed under hydraulic oil.

How to check the engine oil

Open the bonnet and check the dipstick: the level should be between the minimum and maximum marks (page 3-45). Top up through the filler to the maximum mark. Overfilling is dangerous: the manual warns that excess oil can cause the engine to overspeed uncontrollably, so drain any surplus down to the correct level. The capacity is 12–15 litres. Use JCB Extreme Performance 15W-40 for temperatures from −10 to +50 °C or JCB Cold Climate 5W-40 for −20 to +50 °C, depending on the climate the machine works in. The manual stresses that ordinary engine oil must not be used (page 3-11).

How to check the gearbox oil

1. Start the engine and let it idle for 4 minutes so that the oil fills the filter, pump, torque converter, oil cooler and hoses (page 3-68).
2. Stop the engine, remove the key and open the bonnet.
3. Wait for the time shown on the label next to the dipstick (in seconds).
4. The level should be between the end of the dipstick and the maximum mark. Top up through the dipstick tube to the maximum mark, using only the recommended oil.

How to check the axle and hub oil

• Axle centre casing (pages 3-71, 3-73). The machine must be on level ground, otherwise the level reading will be wrong. Apply the park brake, lower the attachments and stop the engine. Clean around the filler plug and remove it: the oil should be up to the bottom of the filler hole. Top up if necessary and refit the plug with its washer.
• Hubs (page 3-72). Check each hub separately. Position the machine so that the OIL LEVEL mark on the hub is horizontal, within 5 mm above or below. Remove the plug: the oil should be up to the bottom of the hole.

The rear axle oil lubricates and cools the oil-immersed brakes, so the type matters: rear axles need an oil suitable for oil-immersed brakes and limited slip differentials. If the rear axle is overheating, the causes are covered in the article JCB 3CX rear axle overheating.

Brake fluid and coolant

Check the brake fluid level at the reservoir under the bonnet; it should be up to the MAX mark (page 3-39). Top up only with JCB Light Hydraulic Fluid; ordinary brake fluid must not be used. If frequent topping up is needed or the level has dropped significantly, the manual requires the brake system to be checked before the machine is used. Check the coolant daily at the expansion tank, between the MIN and MAX marks (page 3-47); remove the cap only when the engine is cold. Check the antifreeze strength every year before the cold season, and renew the coolant every two years.

JCB 3CX / 4CX capacities and lubricants

The gearbox figures in the table are total system capacities; when topping up, go by the dipstick marks only. The data are taken from Section 3 of the manual, issue 9803/3290-16 (pages 3-11, 3-12); for the change intervals see the article JCB 3CX / 4CX routine maintenance. JCB transmission oils are listed under transmission oil and antifreeze under antifreeze. To choose oils and filters for a service, send us the machine model, year of manufacture and serial number.

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