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Jeep Commander XH XK 2006-2010 Workshop Repair Manual digital download

Goal: explain what the cylinder walls are, why they fail, every related component, and give a practical workshop guide (inspection, measuring, honing/repair, reassembly, break‑in) written for a beginner mechanic. Where a spec or specialized machine is required I’ll tell you to use the factory manual or a machine shop. No questions.

Short plain-language overview first
- The cylinder is the round hole bored into the engine block that the piston moves up and down inside. The cylinder wall is the inner surface of that hole.
- The piston + piston rings slide in the cylinder. The rings seal combustion gases and scrape oil back into the crankcase.
- Cylinder walls must be round, smooth (with a fine cross‑hatch surface), and within precise diameter and taper limits. If they’re worn, scored, tapered or glazed, the engine will lose compression, burn oil, smoke, and run poorly.
- Repairs range from light honing (resurface and restore cross‑hatch) to reboring and fitting oversize pistons, or installing cylinder liners/sleeves for severe damage.

Component descriptions (every component directly involved)
- Cylinder bore / cylinder wall: the machined cylindrical cavity in the engine block. Must be concentric and straight, correct diameter and finish.
- Piston: parts that move in the bore, converting expanding gas force to mechanical motion via the piston pin and connecting rod.
- Piston crown/skirts: crown faces combustion; skirts guide the piston in the bore. Skirt clearance matters.
- Piston rings:
- Compression rings (top rings): seal combustion gas.
- Scraper/second ring: helps seal and control oil.
- Oil control ring (usually multi-piece): scrapes oil off cylinder wall and returns it to sump.
- Ring lands: grooves in the piston that carry the rings.
- Wrist pin / gudgeon pin: connects piston to connecting rod.
- Connecting rod and rod bearings: transmit piston motion to the crankshaft; rod bearings must be correct clearance.
- Crankshaft journals: bearings that rotate the rods; if out-of-round they can affect rod geometry and cause wear.
- Cylinder head: contains valves, combustion chamber; mates to block with head gasket.
- Head gasket: seals the combustion chamber and separates coolant and oil passages between head and block.
- Block deck: flat surface where head mates; must be flat; deck and head geometry affect piston-to-valve clearance and sealing.
- Coolant and oil passages: run through the block and near cylinders; corrosion or leaks can affect cylinder integrity.
- Valve train (valves, springs, cam): indirectly related because running issues (pre-ignition, detonation) can damage pistons/walls.
- Fasteners: head bolts/studs, rod bolts — torque sequence and values are critical.

Theory — how the system works and why the cylinder wall matters
- The piston compresses the fuel/air mixture and transmits combustion force to the crankshaft. Rings seal piston to wall so high pressure is trapped above the piston.
- Rings also scrape oil and retain a thin oil film on the cylinder wall for lubrication. The cross‑hatch finish on the walls acts like tiny angled grooves to hold oil.
- Proper clearances (piston-to-wall and ring end gap) allow oil film to form while preventing piston seizure. Too tight = seizure; too loose = blow‑by, noise, oil burning.
- Cylinder wear changes diameter, makes the bore taper or go out-of-round, removes cross‑hatch and damages ring seating -> loss of compression and oil control.
Analogy: the cylinder is like a smooth pipe and the piston is a snug sleeve sliding inside. The piston rings are like springy rubber seals that must press against the pipe. If the pipe is scored, oval, or polished slick, the seals won’t work.

Symptoms that point to cylinder wall problems
- Excessive oil consumption or blue smoke.
- Low compression on one or more cylinders (compression test).
- Blow‑by at the crankcase (pressure when running).
- Poor starting, misfire, loss of power.
- Ticking/piston slap noise when cold (large piston-to-wall clearance).
- Visible scoring in the bore when head or pistons removed.

Inspection and measurement (what to do first)
1. Preliminary tests before teardown:
- Compression test and leak‑down test to identify bad cylinders.
- Check oil condition (fuel dilution, coolant in oil).
2. Remove head and inspect cylinder bores visually under good light for:
- Vertical scores (deep lines), glazing (shiny polish), or scuffing.
- Taper: top often wears more near top ring travel.
3. Measure tooling required:
- Inside micrometer or telescoping bore gauge + outside micrometer for bore diameter.
- Dial bore gauge for accurate diameter and out-of-round.
- Straightedge and feeler gauges for block deck.
- Piston micrometer / caliper to measure piston skirt diameter.
- Plastigage for bearing clearance if you’ll reinstall bearings.
4. Record:
- Cylinder bore diameter at multiple depths (top, middle, bottom) and two perpendicular axes (0°/90°) to check taper and out‑of‑round.
- Piston diameter where skirt and ring lands are measured.
- Ring end‑gap and ring groove wear on pistons.
5. Decide repair path based on measurements:
- If bores within spec and only glazed: honing may be enough.
- Small scoring but within re‑honing limits: hone or slightly rebore and fit oversize pistons.
- Tapered or out‑of‑round beyond limits: rebore to oversize or sleeve.
- Cracked block or severely damaged surfaces: block replacement or sleeve by machine shop.

Repair options and when to use them
- Honing (light or plateau honing)
- Use for glazing, to restore cross‑hatch and improve ring seating when diameter/taper are within spec.
- Best for small wear, not deep scoring.
- Reboring to next oversize
- Machine shop operation. Recommended if bores are worn/tapered beyond limit but block material is sound.
- Requires oversize pistons and rings matched to new bore.
- Cylinder sleeve / insert
- Install a hardened sleeve (wet or dry liner) if wall has deep damage or block can’t be rebored further.
- Often used in worn blocks or when you want a durable repair on older engines.
- Block replacement
- If cracked, scored beyond repair, or cost of machining + pistons > replacement, replace block or engine.

Tools and consumables (basics for a workshop job)
- Safety gear: gloves, eye protection, respirator for solvents, shop rags.
- Engine hoist (if removing engine).
- Standard mechanic’s toolset & torque wrench.
- Cylinder bore gauge / dial bore gauge + micrometers.
- Telescoping gauges and outside micrometer (if no bore gauge).
- Honing tool: flex hone or rotating cylinder hone matched to bore size (hand‑held or drill/bench hone). For best results, machine shop honing stones/brushes and machine are preferred.
- Cylinder hone stones of appropriate grit (two-step: rough then fine or plateau hone).
- Cleaning solvents, hot tank or detergent, compressed air, magnetic pick‑up.
- Ring compressor, piston installation tools, shop lubricant/assembly lube.
- New piston rings, pistons (if oversize), wrist pin clips, rod bearings, head gasket set, oil and coolant, new head bolts if stretch bolts.
- Torque wrench and thread chaser.
- Fine grit sandpaper and stone for light deck cleaning if necessary (be careful).

Step‑by‑step workshop procedure (practical)
A. Preparation and safety
- Have the factory service manual for engine specs (torques, clearances, bore sizes).
- Work on a clean, well-lit bench. Label every part and keep bolts/caps in order.
- Drain oil and coolant. Disconnect battery, remove intake/exhaust manifolds, timing components (mark timing), remove cylinder head(s).
- Remove oil pan and oil pump if required; remove piston/rod assemblies or leave rods in place if only head off for inspection (but you'll need to remove to measure bores fully).

B. Remove pistons and inspect
- Mark rods and caps to maintain orientation (number cylinders, mark cap to rod and direction).
- Remove rod caps (keep bearings in order) and push pistons out the top; catch ring shards and debris.
- Inspect pistons: ring grooves, skirts, scuffs. If rings are stuck or broken, document damage.
- Inspect crank journals and rod bearings for abnormal wear.

C. Clean and initial bore inspection
- Clean the block thoroughly so you can measure accurately. Remove carbon, sludge and debris from oil and coolant passages.
- Measure bores with a dial bore gauge at multiple depths and axes. Record wear, taper, and out-of-round. Compare to factory tolerances.
- Check block deck straightness and head gasket surface.

D. Decide repair: honing vs rebore/sleeve
- If bores within spec and glazing/scuffing mild → hone.
- If bore worn/tapered beyond allowed tolerance → rebore to oversize pistons or install sleeves. For any rebore or sleeve, use a qualified machine shop.

E. Honing procedure (for mild wear)
- Use bench or hand hone appropriate for bore size. Typical approach: a coarse grit to remove glaze, then finer stones to plateau the finish. Aim for uniform cross‑hatch at ~30–45° (consult rings/manual).
- Fit hone with pilot to keep it centered. Use plenty of light oil or honing oil as coolant. Do not overheat; keep removing only small amounts at a time.
- Technique: insert hone, spin while moving up and down smoothly to keep even material removal. Check bore often with bore gauge.
- Final finish: plateau honing (removes peaks left by stones) gives the rings a good seating surface and retains oil. Cross‑hatch angle for oil retention and ring rotation.
- Important: avoid creating out‑of‑round or excessive taper. If you cannot maintain concentricity and correct diameter, stop and send to machine shop.

F. Reboring / Sleeving (machine shop)
- If rebore needed, machine shop rebores to exact oversize and finishes hone to correct size. They will also line bore cylinders if sleeving. They measure crank and rod geometry to maintain proper clearances.
- You will need new pistons and rings sized to the new bore. The machine shop can suggest sizes.

G. Cleaning after machining/honing
- After honing, thoroughly clean every bore with hot solvent, brushes, and compressed air. Remove all abrasive grit and metallic swarf.
- Clean oil galleries with solvent and plug holes and stretchers with compressed air. A magnetic pickup for ferrous swarf is useful.
- Clean block multiple times; install new oil and filter after reassembly.

H. Pistons, rings, and assembly
- Check and file piston ring end‑gap: insert ring into bore (use a piston to square the ring in bore), measure gap with feeler gauge. Adjust only if necessary and within spec.
- Install new rings on pistons in correct order and orientation (markings point up). Stagger ring gaps (don’t line up gaps).
- Lubricate rings and piston skirts with assembly lube or clean engine oil.
- Use ring compressor and install piston back into bore carefully to avoid ring damage. Reinstall rod caps with correct bearings and torque bolts to spec; check crank rotation.

I. Final reassembly
- Replace head gasket and torque head bolts in correct sequence and to proper torque (use new head bolts if required).
- Reinstall timing components, manifolds, oil pump, oil pan, etc. Refill oil and coolant.
- Prime oiling system (turn engine with starter disabled or use oil pump priming tool) to get oil pressure before first start.

Break‑in and testing
- New rings or freshly honed bores require a break‑in procedure to seat rings and form a stable oil film.
- Typical break‑in: start engine, run at varying RPM (no constant idle), avoid lugging at light throttle, vary load gently for first 20–50 minutes. Follow the engine manual’s recommended break‑in rpm/period.
- Change oil and filter after the initial break‑in interval (usually 50–100 miles) to remove metal particles.
- Recheck compression and look for oil consumption and leaks.

What can go wrong (common mistakes and failures)
- Incorrect measurement or skipping measurements: leads to wrong repair choice and repeat failures.
- Dirty/contaminated block after honing: swarf left in oil galleries accelerates bearing and cylinder damage.
- Over‑honing or removing too much material: creates out‑of‑round or excessive taper, forcing rebore/sleeve.
- Using a drill‑mounted hone incorrectly: can create chatter, uneven hone, and poor cross‑hatch.
- Wrong piston-to-wall clearance: too tight → seizure; too loose → piston slap, noise, poor compression.
- Incorrect ring end gaps or aligned ring gaps → compression leakage and rapid wear.
- Incorrect ring orientation or upside‑down installation → poor sealing and oil control.
- Improper rod bearing fit or torque → bearing failure and crank damage.
- Improper cleaning of head/block surfaces or reused damaged head gasket → coolant/oil mixing and head gasket failure.
- Not following torque sequences or using used/stretched head bolts → leaks and warping.
- Failure to check piston-to-head clearance (valve-to-piston clearance) after installation, especially if pistons were replaced/oversized.
- Poor break‑in procedure → rings won’t seat, leading to high oil consumption and low compression.
- Ignoring root causes: e.g., if scoring caused by coolant loss/overheating or detonation, repairing bore alone without fixing root cause will repeat failure.

Practical tips and analogies
- Think of the cylinder wall like a finely honed tea can — you want the inside to be perfectly round and finished so the piston (a snug mug) can slide smoothly. The cross‑hatch is like tiny angled valleys to hold a thin film of lubricant — without it the piston would ride on dry metal.
- When honing, imagine sanding a wooden dowel inside a tube: you must move the sandpaper evenly so the tube remains round; stop frequently to measure.
- Always keep everything clean. Even a small grain of grit is like sandpaper between piston and wall and will ruin the surface quickly.
- When in doubt with measurements or machining, use a competent machine shop. Honing/boring errors are hard to reverse.

Final words (safety and sources)
- Use the Jeep/Commer factory workshop manual for torque values, piston specs, ring end‑gaps and exact clearances for the XH/XK engine variant you’re working on.
- When repair requires reboring or sleeving, prefer a reputable machine shop rather than guessing DIY.
- Safety: handle heavy parts with proper lifting gear, dispose of oil/coolant properly, and work in a ventilated area.

This gives you the theory, the components, the diagnostic checks, the repair choices, step‑by‑step workshop actions, what to watch out for, and the mistakes to avoid. Follow the service manual specs for your specific engine and use a machine shop when the job is beyond a hand‑hone.
rteeqp73

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