The repair of the bearing shell of a diesel engine must be carried out after a detailed inspection and restoration of all faults in the cylinder block and crankshaft.
Preparation work before repairing and scraping the bearing shell
(1) Prepare various tools such as socket wrenches, scrapers, etc.
(2) Prepare the cleaning oil and wiping cloth.
(3) Prepare the adjusting shims (0.05-0.2mm thick copper shims) for the main bearing and connecting rod bearing.
(4) Clean the crankshaft, connecting rod bearing seat, bearing cover, and bearing shell, and block the oil holes on the bearing seat. The purpose of blocking its oil hole is to prevent impurities from leaking into the oil hole on the bearing seat and blocking the lubricating oil passage when scraping the tile.
Repair and maintenance of connecting rod bearings
- Repair method
(1) Lift the crankshaft onto a dedicated bracket or stand it on the flywheel.
(2) Clean the connecting rod journal and bearing. If there are roughness or scars on the shaft neck, cut the 00 # sandpaper to the same width as the shaft neck and stick it on Apply a small amount of engine oil to smooth out the roughness.
(3) Install the selected bearing shells and connecting rods on the shaft neck, tighten the screws until there is resistance to rotation, then rotate back and forth 3-4 turns, and then remove the connecting rod bearing shells, check the contact with the shaft neck, and perform scraping.
When starting the scraping process, the contact between the bearing and the journal is usually at both ends of each bearing. After several rounds of scraping, it should be noted that when the contact surface expands to more than one-third of the length of the bearing, 2-3 thin copper sheets with a thickness of 0.05mm should be placed at the contact between the two end faces of the bearing seat (be careful not to place them at the joint between the two ends of the bearing), which can reduce the amount of scraping required for the bearing and shorten its scraping time; When repairing, it is necessary to use the left hand to support the connecting rod or tile cover, the right hand to level the scraper, and the wrist to move the scraper from the outside to the inside according to the contact situation. The scraper should be lifted and dropped steadily, and the sharpness of the scraper should be maintained at all times; When starting to scrape, it is required to scrape more heavily and less lightly or not at all, in order to quickly scrape out a uniform contact surface.
Near the joint surface, start to scrape again appropriately, and scrape less or no halfway; When the contact surface of the bearing shell is almost complete, adjustment should be the main focus, with light scraping and small scraping, until the torque is sufficient, the tightness is appropriate, and the contact surface reaches 75% or more; During the scraping process, if the tightness is appropriate but the contact surface does not meet the requirements, the gasket can be reduced appropriately before continuing the scraping; In general, after scraping the bearing, 1-2 gaskets should be retained to adjust the tightness of the bearing after the diesel engine has been working for a period of time; In special circumstances, such as when the scraping amount of the bearing is too small, a copper gasket of appropriate thickness can be added to the back of the bearing. However, this method can only be used during medium and minor repairs and must not be used during major repairs.
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