Doosan DX420LC-5 Excavator Service Manual

How to Use Guide Manual

This manual provides information for servicing the Excavator. All service procedures are broken down into detailed steps, listed in their recommended sequence. The manual uses both photographs and drawings to help locate and itemize components. The table of Contents on the preceding pages is your best tool for finding the service procedure you need. Be certain to observe all Safety information included in these pages.

A schematic of each of the major engine systems is provided at the beginning of the section of the manual devoted to troubleshooting and repairing that particular system.

Basic safety precautions are list in the Safety section of the Service Manual. Additional safety precautions are list in the Safety section of the owner/operation/maintenance publication. Specific safety warnings for all these publications are provided in the description of operations where hazards exist. WARNING labels have also been put on the product to provide instructions and to identify specific hazards.

Manual Instruction Extract :

Removing the Crankshaft
1. Remove crankshaft gear as described in Removing the crankshaft gear.
2. Remove crankshaft pulley as described in the work description “Removing the Drive Belt” on page 4-1-144.
3. Remove oil sump, oil pump suction pipe, ladder frame and oil pump as described in the relevant work descriptions.
4. Remove pistons and connecting rods according to the work description “Removing the Piston” on page 4-1-136.
5. Remove main bearing caps and main bearings.
NOTE: The main bearings and main bearing caps are marked and must be reinstalled in the same place.
6. Lift out the crankshaft.

Checking Main Bearing Cap for M18 Main Bearing Screws There have been instances where the heads of main bearing cap screws break because of high load.
In case of any of these symptoms it is recommended that main bearing caps are checked. Remove oil sump and check carefully that all main bearing screws are secure. In some cases, the screw head is in place but it has cracked and lost its clamping force.
Replace the torsion damper when performing repairs because of broken main bearing cap screws. The torsion damper must be replaced because it often breaks down shortly after replacing the main bearing cap screws.
1. Remove main bearing caps.
NOTE: The main bearings and main bearing caps are marked and must be reinstalled in the same position.