Maintenance & fault isolation

Access · Lower cowl, heat shroud removed

Tools & materials · Inspection mirror · Flashlight · Pressure test kit (optional)

Warning · A cracked muffler can fill the cabin with carbon monoxide.

1. 1.Remove the heat shroud.
2. 2.Inspect the muffler for cracks, bulges, burned spots, especially around welds and the inner baffles.
3. 3.Pressure test or immerse test if any doubt.
4. 4.Inspect the SCAT ducts and heat valve.
5. 5.Reinstall shroud; run with CABIN HEAT on and check with a CO detector.

Ref: Cessna SEB / AD for exhaust systems

Access · Battery box (firewall / tailcone per serial)

Tools & materials · Digital multimeter · Hydrometer or capacity tester · Baking soda solution · Terminal brush · Torque wrench

Warning · Batteries emit hydrogen — no sparks or flames. Wear eye protection when handling acid.

1. 1.Master OFF, STBY BATT OFF; disconnect the negative cable first, then positive.
2. 2.Remove the battery and inspect the box for corrosion; neutralise any acid with baking soda solution and repaint.
3. 3.Check the box drain and vent tubes are clear.
4. 4.Flooded battery: check electrolyte level above plates and specific gravity (approx. 1.260–1.280 charged). Sealed: run capacity test.
5. 5.Clean terminals; reinstall positive first, negative last; torque; apply corrosion inhibitor.
6. 6.Power on and check bus voltage on the G1000 (approx. 24–25 V battery only, 28 V with engine running).

Ref: Cessna 172 MM Ch. 24 / battery CMM

Access · Upper and lower cowling

Tools & materials · Belt tension gauge or torque wrench · Straightedge

1. 1.Inspect the belt for cracks, glazing, fraying.
2. 2.Measure tension per method (deflection or slip torque at the alternator pulley nut).
3. 3.Adjust by loosening the adjusting arm bolt and moving the alternator; torque the bolts.
4. 4.New belts: recheck after 10 h run-in.

Ref: Lycoming SI 1129 / Cessna MM Ch. 24

Access · Lower cowl, wing root fairings

Tools & materials · Fuel sampler · Safety wire · New O-ring

Warning · Fire hazard — no smoking, ground the aircraft.

1. 1.Fuel shutoff OFF. Remove the strainer bowl, clean the screen in solvent.
2. 2.Install a new O-ring, reinstall bowl, torque and safety-wire.
3. 3.Fuel shutoff ON, check for leaks with fuel pump ON.
4. 4.Drain all 13 sumps and check for water and debris.

Ref: Cessna 172 MM Ch. 28

Access · Aircraft on jacks or wheel raised

Tools & materials · Rivet tool for linings · Pressure bleeder pot · MIL-PRF-5606 fluid

1. 1.Remove back plate bolts and slide the caliper off the disc.
2. 2.Replace worn linings with the riveting tool.
3. 3.Reinstall; torque bolts and safety.
4. 4.Bleed from the bottom up: pressure pot to the caliper bleeder, fluid flows up to the reservoir until no bubbles.
5. 5.Condition new linings with several medium-speed taxi stops.

Ref: Cessna MM Ch. 32 / Cleveland Wheels & Brakes manual

Access · Upper cowling, all top plugs removed

Tools & materials · Differential compression tester with master orifice · 80 psi regulated air

Warning · Hold the propeller firmly — 80 psi will rotate it violently if not exactly at TDC.

1. 1.Test with the engine warm.
2. 2.Bring each cylinder to TDC on compression; apply 80 psi.
3. 3.Read the cylinder gauge; listen for leakage: oil filler = rings, exhaust = exhaust valve, intake = intake valve.
4. 4.Compare with the master orifice calibration reading (lowest acceptable value).
5. 5.Borescope any low cylinder before deciding on removal.

Ref: Lycoming SI 1191A / AC 43.13-1B

Access · Upper cowling, spark plug access

Tools & materials · Timing light / buzz box · TDC indicator · Degree wheel

1. 1.Remove the top spark plug from No. 1 cylinder.
2. 2.Rotate the propeller in normal direction until No. 1 reaches top dead centre on the compression stroke.
3. 3.Back up past 25° BTDC and come forward to the timing mark (25° BTDC for IO-360-L2A).
4. 4.Connect the timing light to each magneto's P-lead terminal and ground; the light should change as the points open exactly at the mark.
5. 5.Adjust by loosening the mounting clamp and rotating the magneto.
6. 6.Check internal timing ('E-gap') if within the overhaul interval guidance.

Ref: Lycoming Operator's Manual / Slick or Bendix magneto manual

Access · Upper/lower cowling

Tools & materials · Deep socket 7/8 in · Gap gauge · Plug cleaner · Torque wrench · Anti-seize compound

1. 1.Remove plugs in order and place them in a numbered tray (position tells you about each cylinder).
2. 2.Inspect electrodes: grey-tan normal, black sooty = rich, oily = ring/valve issue, lead fouling = leaning practice.
3. 3.Clean, gap and test plugs.
4. 4.Rotate: top to bottom and swap sides (reduces electrode erosion due to polarity).
5. 5.Install with new gaskets, anti-seize on threads (not first 2), torque.

Ref: Champion AV6-R / Lycoming SI 1042

Access · Upper cowling removed

Tools & materials · Oil drain hose / quick drain · Filter wrench · Torque wrench · Filter cutter · Safety wire pliers & 0.032 in wire

Warning · Hot oil causes burns. Treat the propeller as live.

1. 1.Run the engine to operating temperature so contaminants are suspended.
2. 2.Shut down, master OFF, mags OFF, key removed. Chock wheels.
3. 3.Drain oil through the quick-drain valve into a container.
4. 4.Remove the safety wire and spin-on filter. Cut the filter open and inspect the pleats for metal.
5. 5.Lubricate the new filter gasket with clean oil, install hand-tight then to specified torque; safety-wire it.
6. 6.Refill with the approved grade (e.g. 15W-50 or SAE 50 ashless dispersant) to 6–8 qt.
7. 7.Ground run; check for leaks and normal oil pressure within 30 s.
8. 8.Record the change in the engine logbook.

Ref: Lycoming SI 1014 / Cessna MM Ch. 12