Can New Crankshaft and New Bearings Be Installed Directly?
2 Answers
New crankshaft and new bearings cannot be installed directly. Here are the details: 1. Introduction: The crankshaft is the most important component in an engine. It bears the force transmitted by the connecting rod and converts it into torque, which is then output through the crankshaft to drive other engine accessories. The crankshaft is subjected to centrifugal forces from rotating masses, periodically varying gas inertial forces, and reciprocating inertial forces, causing it to endure bending and torsional loads. Therefore, the crankshaft must have sufficient strength and stiffness, with wear-resistant journal surfaces, uniform operation, and good balance. 2. Casting Technology: Melting: Obtaining high-temperature, low-sulfur pure molten iron is key to producing high-quality ductile iron. Molding: Airflow impact molding is significantly superior to clay sand molding, enabling high-precision crankshaft castings. The sand molds produced by this process feature no rebound deformation, which is particularly important for multi-throw crankshafts. Electroslag Melting: Electroslag remelting technology applied to crankshaft production allows cast crankshafts to potentially match the performance of forged ones. It also offers advantages such as fast R&D cycles, high metal utilization, simple equipment, and superior product performance.
I just went through this. Never install a new crankshaft and bearings dry! Before assembly, you must evenly coat both the crankshaft journals and bearings with clean engine oil, otherwise the initial friction will be too high and cause immediate bearing failure. The most critical step is using plastigauge to check bearing clearance - install the bearings, torque the bolts to manual specifications, then remove and measure the squashed plastigauge strip thickness. If clearance is wrong, you'll need different sized bearings. Bolts must be tightened in three stages following the service manual's sequence and torque specs, finishing with a 90-degree turn using an angle gauge. After installation, manually rotate the crankshaft several revolutions to confirm no binding before adding oil. On first startup, run the engine at 2000 RPM for 20 minutes to properly seat the new bearings - skip this step and you'll be paying for a major rebuild.
