Can Subaru Replace Piston Rings?
3 Answers
Subaru can replace piston rings. Reasons for replacing piston rings: Practice has shown that the wear and failure rate of piston rings is much faster than the rate at which cylinder wear reaches its limit. Therefore, often between two major engine overhauls or during maintenance, since the cylinder liner wear is relatively light and does not require cylinder honing or replacement, the engine's performance can be improved by replacing the piston rings. Precautions for replacing piston rings: Check and adjust the ring end gap, side clearance, elasticity, and leakage rate. Select piston rings that match the repair dimensions of the cylinder and piston. Alternatively, the old top compression ring on the piston can be moved to the first ring groove, and the newly selected rings can be installed in the lower ring grooves. This can prevent poor sealing between the new rings and the cylinder wall, which could lead to gas leakage and oil consumption. Correct the wear ridge at the top of the cylinder. A scraper can be used for this correction. When scraping, start from the inside and scrape outward to avoid damaging the cylinder wall surface. Metal shavings from scraping should be properly handled and must not be allowed to fall into the crankcase. If the wear ridge is not corrected, the new rings will impact the ridge during operation, causing the rings to crack or the ring lands to break, potentially leading to cylinder scoring. The end gap of the new rings should be filed to the correct size based on the cylinder position when the piston is at bottom dead center. Special attention should be paid: do not use the maximum wear point at the cylinder's upper wear ridge as the basis for determining the end gap of the rings.
Yes, piston rings can definitely be replaced. I'm quite familiar with this procedure. Just the other day, I helped a friend deal with oil burning issues in their Subaru Forester, which turned out to be caused by piston ring problems. Replacing rings in a boxer engine is more complex than in a conventional engine - you have to hoist the entire engine out of the bay. The technician needs to disassemble the cylinder head and oil pan, then remove all the piston connecting rod assemblies. Special attention must be paid to the factory-specified ring end gaps and torque parameters. If things aren't aligned properly during reassembly, cylinder scoring can occur instantly. After replacement, you need to run specialized break-in oil for about 500 kilometers, followed by cylinder pressure and exhaust emission checks to complete the job. This really requires professional equipment - I'd recommend going directly to a Subaru specialist workshop.
I've been driving a Subaru Impreza for over a decade, and the piston rings are most prone to issues when the turbo roars. During the last overhaul, I upgraded to reinforced piston rings—the labor cost was three times more expensive than the parts. The horizontally opposed engine is particularly tricky to disassemble and reassemble, with two cylinder banks arranged opposite each other, requiring the entire crankcase to be dismantled. Experienced mechanics use plastic zip ties to secure the piston rings before installing them into the cylinder bores to prevent misalignment of the ring gaps. The key is to inspect the cylinder walls for scratches—minor wear should be polished with specialized sandpaper. If the oil consumption is exceptionally severe, it's best to replace the pistons along with the rings.
