How to relieve hydraulic pressure in the hydraulic circuit of a CAT excavator.

 How to relieve hydraulic pressure in the hydraulic circuit of 312D2 and 313D2 excavators

 Steps to relieve pressure:

 

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Before servicing a hydraulic circuit, you must relieve the hydraulic pressure in that circuit. Before disconnecting or removing any hydraulic lines from the following hydraulic circuits, relieve the pressure in that circuit.

• Boom hydraulic circuit 

• Stick hydraulic circuit 

• Bucket hydraulic circuit 

• Swing hydraulic circuit

 • Travel hydraulic circuit 

• Attachment hydraulic circuit (if equipped) 

• Pilot hydraulic circuit

 • Return hydraulic circuit  

 Hydraulic pressure relief for multiple hydraulic circuits

WARNING: Hot oil or hydraulic oil pressure can cause personal injury.

After the engine is stopped, hydraulic oil pressure remains in the hydraulic system. Serious injury could result if pressure is not relieved before servicing the hydraulic system. Before removing hydraulic system components or lines, make sure all work tools are lowered to the ground and the hydraulic oil is cold. Remove the filler cap only when the engine is stopped and the filler cap is cool enough to touch with your bare hands.

 

NOTICE During inspection, maintenance, testing, adjustments, and repairs of the product, care must be taken to ensure that any fluids that are drained are contained. Before opening any compartment or disassembling any component that contains fluids, have a suitable container ready to collect the fluids. Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for appropriate tools and supplies for collecting and containing fluids on Cat products. Dispose of all fluids in accordance with local regulations and requirements

 

Perform the following steps to relieve hydraulic pressure from multiple hydraulic circuits of the main hydraulic system. 1. Park the machine on level surface. 

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2. Fully retract the boom cylinder rod. Adjust the bucket position so that it is parallel to the ground. Lower the boom until the bucket is level with the ground. See Illustration 1.

 3. Shut down the engine. 

 

4. Turn the engine start switch to the on position, but do not start the engine. 

 

 5. Return the hydraulic start control lever to the unlocked position. 

 

 6. Move the control handle or pedal to the full position for only the hydraulic circuit that needs service. This will relieve high pressure only in that circuit. This will also relieve any pressure that may be present in the pilot hydraulic circuit. Note: If the hydraulic circuit that needs service requires the activation of an operating switch, activate the appropriate operating switch on the hydraulic circuit. 

 

7. Return the hydraulic start control lever to the locked position. 

 

8. Start the engine. 

 

9. Return the hydraulic start control lever to the unlocked position. Do not move any control handle or pedal from the neutral position during this step. Do not activate any switches during this step. 

 

10. Return the hydraulic start control lever to the locked position. 

 

11. Shut down the engine. 

 

12. Repeat steps 4 through 11 for each of the other hydraulic circuits that need service. 

 

13. After relieving hydraulic pressure from each target hydraulic circuit, place the hydraulic start lever in the locked position. 

 

14. Turn the engine start switch to the OFF position. 

 

 15. Slowly loosen the filler plug on the hydraulic tank to release pressure. The filler plug should remain loosened for at least 45 seconds. This will release any pressure that may be present in the return hydraulic circuit. 

 

16. Tighten the filler plug on the hydraulic tank to the specified torque. 

 

17. Pressure is now relieved from the multiple hydraulic circuits that require service and lines and components can be disconnected or removed from these hydraulic circuits.

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the hydraulic release of the single hydraulic circuit of the caterpillar311D LRR excavator

This article introduces the hydraulic release of the single hydraulic circuit of the caterpillar311D LRR excavator

                                                       warn！

The pressure of rolling hot oil or hydraulic oil can cause harm to

personnel.

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After the engine shutdown, the hydraulic oil pressure will

remain in the hydraulic system. Serious injury may occur

without prior pressure release prior to repairs to the

hydraulic system.

When removing the components or lines of the hydraulic

system, ensure that all work machines are lowered to the

ground and that the hydraulic oil temperature is cold. Remove

it only when the engine is stopped and the filler cap is

cooled to manual touch. 

 

pay attention to

During inspection, maintenance, testing, adjusting and

servicing the engine. Prepare a suitable container for

fluid collection before opening or dismantling any stored

parts.

For tools and supplies suitable for the collection and

delivery of liquids on Caterpillar products, see Special

publications, NENG 2500, "Caterpillar Agents Tools

Catalogue."

Dispose of all liquids in accordance with local regulations and

regulations.

Follow the following steps to release the hydraulic pressure from the single

hydraulic circuit of the main hydraulic system.

 

1. Park the machine on the horizontal ground.

 

  

 
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2. Fully withdraw the bucket rod cylinder connecting rod. Adjust the bucket

position so that the bucket is parallel to the ground. Lower the boom

until the bucket falls horizontally on the ground. See the illustration

1.

 

3. Turn off the engine. 

 

4. Turn the engine start switch to the on position, but not starting the

engine.

 

5. Place the hydraulic start control lever in the unlock position. 

 

6. Move only the joystick or pedal of the repaired hydraulic loop to the

full position. This will only release only the high pressure in this

single hydraulic loop. This will also release any pressure that may

exist in the pilot hydraulic circuit.

Note: If the repaired hydraulic circuit needs to start the operating

switch, start the corresponding operating switch in the hydraulic

circuit. 

 

7. Place the hydraulic start control lever in the locked position. 

 

8. Turn the engine start switch to the off position. 

 

9. Slowly release the filling port plug on the hydraulic tank to release

the pressure on the hydraulic tank. The fill port plug shall remain

loose for at least 45 seconds. This releases the pressure that may be

present in the return hydraulic circuit. 

 

10. Tighten the filling plug on the hydraulic tank to the specified torque. 

 

11. The pressure in the single hydraulic circuit requiring repair is now 

 

released and the lines and components can be disconnected or removed from

the hydraulic circuit.

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How to Deal with the Alarm and Speed limit of 1400RPM when the Doosan Excavator Engine is Working

This article mainly introduces how to deal with the problem of alarm and speed limit of 1400RPM when the doosan excavator engine is working.

 

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Fault phenomenon:

An alarm occurs during engine operation and the speed is limited to 1400RPM. 

 Inspection Method: 

 1) The vehicle has been working for 2200 hours, the equipment speed limit is 1400rpm, and the fault code retrieved is P1251: fuel balance leakage;

2) Check that the low-pressure oil line pressure is 70kpa, which is on the low side (normally around 90kpa); after cleaning the oil-water separator, the low-pressure pressure has increased, but the fault still occurs from time to time;

3) After low-pressure inspection, check the high-pressure system, connect the software to perform cylinder disconnection test and crankshaft acceleration test. There is no obvious abnormality in the working status of each cylinder;

4) Check that the resistance of the IMV valve is 3.2 ohms and is normal. Since the IMV valve is easy to disassemble, the 2018-04-27 13:49 Wang Xiaobo IMVi valve was replaced first and tested. After replacement, the equipment works normally.  

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When the P1251 fault code occurs in the engine, the casing should be arranged from simple to difficult. First, check the low-pressure fuel oil line, and then conduct troubleshooting of the high-pressure well rail system.

 

How to Troubleshoot the Problem That the Coolant Temperature of the Excavator's Electronically Injected Diesel Engine is Too High

1. Cause of failure  

(1) The radiator fins are dirty, debris or damaged. 

 (2) Insufficient coolant. 

 (3) The radiator cap or pressure relief valve is damaged.  

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(4) There is air in the cooling system.

 (5) The cooling fan is not working properly and the fan belt is too loose.  

(6) The thermostat is damaged. 

 (7) The cooling system pipeline is blocked or leaking. 

 (8) The coolant temperature gauge is damaged. 

 (9) The water pump impeller is damaged or corroded.

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2.Fault  

(1) Visually inspect the cooling system for broken hoses or other throttling components. 

 (2) Check the radiator fins for dirt, debris and damage. Remove dirt and debris, clean and flush the radiator, and straighten any bent fins. 

 (3) Check the coolant level and add coolant if necessary.

  (4) Check whether the cooling system is leaking and repair the leaking area immediately. 

 (5) Check the cooling system pressure. 

 (6) Check the pressure relief valve and radiator cap. Clean and replace parts if necessary. 

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 (7) Check whether the seat surface of the pressure safety valve and the radiator cover are clean and damaged. 

 (8) Check whether there is combustion gas in the cooling system and whether there are bubbles in the coolant. If there are bubbles, combustion gases may have entered the cooling system.  

(9) Check whether the cooling fan is working normally. Check that the belt and pump are working properly.  

(10) Check whether the thermostat is operating correctly. If necessary, replace the thermostat.  

(11) Compare the coolant temperature reading from the ET to the coolant temperature reading from the mechanical measuring instrument. 

(12) Check whether the water pump impeller is damaged or corroded. Repair or replace water pump if necessary.  

(13) Check whether the fault is caused by system overload, reduce the load and check whether the condition recurs.

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How to Inspect the Caterpillar Excavator Air Intake and Exhaust System

How to inspect the caterpillar325c excavator air intake and exhaust system 

 1. Inspection of air intake and exhaust systems 

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 (1) Inspection of air intake resistance. If there is resistance in the intake and exhaust systems, it will be the 1U-5470 engine pressure assembly (Figure 3-1-46). 

 1) Check the intake pipe and exhaust pipe of the engine air filter to ensure that the pipes are not leaking.

 2) Check the engine air filter element. Use a clean engine air filter

 3) Check whether there are traces of dirt on the clean side of the engine air filter element. If traces of dirt are observed, it means that the contaminants have entered the engine air filter element and/or filter element seal. . NOTE: Hot engine parts can cause burns. Allow the engine and parts to cool before servicing the engine. Contact with a running engine can result in burns from hot parts or damage from rotating parts. When working on a running engine, avoid contact with hot or rotating parts. 

 4) Measure using the differential pressure gauge in the 1U-5470 engine pressure test assembly  

①As shown in Figure 3-1-50, connect the vacuum port of the differential pressure gauge to test position 3. Test location 3 may be anywhere on intake manifold 2 behind engine air filter 4 and in front of wheel booster 1. 

 

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 ②Open the pressure port of the differential pressure gauge to allow it to communicate with the atmosphere. 

 ③Start the engine. Run the engine at high idle speed with no load. 

 ④Record the pressure value, multiply this pressure value by 1.8, and then compare it with the corresponding value below. There is resistance to airflow through an old engine air filter. There will also be some resistance to airflow through a clogged engine air filter. in In the above two cases, the resistance must not exceed 6.2kPa; the resistance of the air flowing through the new air filter element must not exceed 3.7kPa. 

 (2) Inspection of exhaust resistance. Back pressure is the pressure difference between the exhaust pressure at the elbow outlet and the atmospheric pressure. The tools required to check exhaust resistance are 1U-5470 engine pressure components (Figure 3-1-46). NOTE: Hot engine parts can cause burns. Allow the engine and components to cool before servicing the engine. Contact with a running engine can result in burns from hot parts or injury from rotating parts. When working on a running engine, avoid contact with hot or rotating parts. Use the differential pressure gauge in the 1U-5470 Engine Pressure Test Assembly to measure exhaust backpressure. Use the following steps to measure exhaust back pressure. 

 1) As shown in Figure 3-1-51, connect the vacuum port of the differential pressure gauge to test position

 

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    2. Test location 2 may be anywhere on exhaust pipe

 3 behind turbocharger 4 and in front of muffler 

1. 2) Open the pressure port of the differential pressure gauge to allow it to communicate with the atmosphere.  

3) Start the engine. Run the engine at high idle speed with no load. 

 4) Record the pressure value. 

 5) Multiply the value in step 4) by 1.80. 

 6) Compare the value in step 5) with the value below. The exhaust back pressure must not be greater than 10.OkPa.