At what level of cylinder liner wear does replacement become necessary?
2 Answers
Cylinder liners generally need replacement when wear exceeds 0.50mm. Here's more detailed information: 1. According to traditional engine maintenance standards, piston rings come in oversized variants of 0.25mm, 0.50mm, 0.75mm, and 1.00mm beyond standard dimensions, which serve as benchmarks for cylinder boring; 2. In reality, cylinder liner wear isn't uniform, often presenting as eccentric ovalization or scoring. Since boring can't perfectly match irregular wear patterns, the actual measured wear value is typically increased by 0.25mm as the final boring standard (occasionally up to 0.50mm, but surface hardness and strength limitations prevent excessive enlargement).
Actually, there's no absolute standard for cylinder liner wear, but I've picked up a few tricks from veteran mechanics. The most obvious sign is scoring marks - if there are clear vertical scratches on the cylinder walls that you can feel with your fingers, it's basically done for. Another indicator is oil consumption: blue smoke from the exhaust pipe plus losing more than half a liter of oil every 1,000 kilometers usually means excessive clearance between piston rings and cylinder walls. When I overhauled my old Jetta last time, the cylinder gauge showed over 0.15mm wear - the pistons were rattling badly inside. After replacing the liners, fuel consumption dropped by two liters instantly. Oh, and that 'knocking' sound during cold starts is another telltale sign, especially noticeable in winter. If replacement is needed, modern boring and repair techniques have improved - for not-too-severe wear, nano-coating restoration is more cost-effective than full engine replacement.
