Contents: Inspection ↓ Choice ↓
Inspection
Typical bearing defects
Even though the main and connecting rod bearings are subject to replacement during an engine overhaul, they should be carefully inspected as they can provide valuable information regarding the condition of the engine.
Bearing failure may be due to lack of lubrication, dirt or other foreign particles, engine overload, or corrosion. Regardless of the cause of bearing failure, the cause of the bearing failure must be corrected before the engine is reassembled.
When inspecting the bearings, remove them and arrange them in the same order as they were installed on the engine. This will help identify the corresponding crankshaft journal and make troubleshooting easier.
Foreign particles can enter the engine in a variety of ways. Metal particles can be found in the engine oil as a result of normal engine wear. Small particles can enter the bearings along with the engine oil and easily become embedded in the soft bearing material. Large particles entering the bearing will scratch the bearing or crankshaft journal. The best way to prevent bearing failure for this reason is to thoroughly clean all internal engine surfaces and keep them clean when assembling the engine. Frequent and regular oil and filter changes are also recommended.
Insufficient lubrication of the crankshaft journals can be caused by many different reasons, such as high oil temperatures, engine overload, and oil leaks. The driving style also affects the longevity of the bearing. A fully open throttle at low engine speeds creates high loads on the bearings and squeezes out the oil film from the contact area. These loads lead to cracks in the working part of the bearing, which weakens the bearing and can lead to the antifriction layer being torn off from the steel base.
Short-distance driving causes bearing corrosion because the engine does not reach a stabilized operating temperature, which removes water vapor and corrosive gases. These vapors and gases condense in the engine oil, forming acid and sediment. The acid gets to the bearings along with the engine oil, and bearing corrosion begins.
The full article is posted on the website [Toyotaman.ru]
Incorrect selection of bearings during engine assembly also leads to bearing failure. Bearings installed with preload leave insufficient bearing operating clearance, resulting in a reduced or absent oil layer for lubrication.
Choice
If the removed bearing shells are worn or damaged, or the bearing clearance is outside the acceptable range, new bearings must be selected.
Main bearings
Location of main bearing identification marks on 3VZ-FE V6 engine | 
Location of main bearing identification marks on 5S-FE engine |
Location of main bearing identification marks on the front of the cylinder block (A) and on the front crankshaft balancer (B) on the 1MZ-FE V6 engine
If the number on the main bearing is worn out, read it on the surface of the cylinder block that mates with the oil pan. On the 1MZ-FE V6 engine, the block numbers are on the front of the cylinder block near the first main bearing, and the crankshaft numbers are on the first crankshaft balancer.
Adding the cylinder block number to the crankshaft journal number will give the recommended bearing size for 5S-FE and 3VZ-FE engines. To determine the bearing size on a 1MZ-FE engine, use the table.
Determining the size of the main bearing for the 1MZ-FE engine
Total Quantity – Tag Number | |||||
Cylinder block (A) + Crankshaft (B) | 0 – 5 | 6 – 11 | 12 – 17 | 18 – 23 | 24 – 28 |
| The bearing used | 1 | 2 | 3 | 4 | 5 |
Connecting rod bearings
Applying identification marks to the cap and lower connecting rod head
If a standard crankshaft is used, it is necessary to install a connecting rod bearing, the number of which is stamped on the connecting rod head.
All bearings
Remember that the final bearing size selection is determined by bearing clearance.