Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Compression Test - Interpreting Compression Readings
2005 Mazda B2300 AutomaticSECTION Compression Test - Interpreting Compression Readings
- If compression improves considerably, piston rings require service.
- If compression does not improve, valves are sticking or seating improperly.
- If two adjacent cylinders indicate low compression pressures and squirting oil on piston does not increase compression, the head gasket may be leaking between cylinders. Engine oil and/or coolant in the cylinders could result from this condition. Use the Compression Pressure Limit Chart when comparing cylinder compression readings to determine if the lowest reading is at least 75 percent of the highest reading.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.