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AV-SCANNER / Service function guides / Engine and oil
This guide provides a complete, professional workflow for performing compression and leak-down tests to prove the mechanical health of each cylinder. It is written for working mechanics and serious DIYers who need to diagnose misfires, oil consumption, rough running, or verify an engine before purchase or after a rebuild. You will learn how to prepare the vehicle safely, execute both tests step by step, interpret the readings against factory service information, and use the results to isolate valve, ring, or head gasket faults. By the end, you will be able to document cylinder condition accurately and recommend the correct repair path with confidence.
Guidance is general and covers many makes. Exact procedures and values vary by model, so confirm them in the factory service information for your vehicle.
Download all 11 sections as a branded PDF to use in the workshop.
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