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Jeep Grand Cherokee 1999-2004 WJ WG Factory Workshop Service Repair Manual download

- Safety first (read and follow these exactly)
- Wear safety glasses and gloves.
- Work on a flat surface, engage parking brake, put wheel chocks on wheels that remain on the ground.
- Disconnect the negative battery terminal before doing electrical work.
- Never rely on a jack alone — always support the vehicle on rated jack stands on the manufacturer’s recommended lift points.
- If you’re unsure at any point, stop and get professional help.

- Basic tool kit (what each tool is, why it’s needed, and how to use it)
- Hydraulic floor jack
- Description: Low-profile jack with a handle used to lift the vehicle.
- Why: Needed to raise the vehicle enough to place jack stands and remove wheels.
- How to use: Place under a solid frame/lift point, pump handle to lift slowly, don’t get under vehicle until it’s on jack stands.
- Jack stands (rated to vehicle weight)
- Description: Adjustable metal stands with locking pin/rack.
- Why: Required to safely support the vehicle while you work.
- How to use: Set height, place under frame/axle, lower vehicle onto them, test stability before going under.
- Wheel chocks
- Description: Rubber or plastic wedges.
- Why: Prevents vehicle rolling while lifted.
- How to use: Place behind wheels on the ground opposite the side being lifted.
- Lug wrench / breaker bar and 3/4" socket (or correct size for your lug nuts)
- Description: Long-handled tool for breaking and tightening lug nuts.
- Why: Remove wheels to access suspension components.
- How to use: Break lugs while car is on ground, then remove after vehicle is raised.
- Torque wrench (click-style, ft·lb range)
- Description: Wrench that applies a precise torque and clicks when reached.
- Why: Re-torque lug nuts and suspension bolts to factory spec to avoid loose parts or overtightening.
- How to use: Set required torque value, tighten until you hear/feel the click; consult a manual for exact torque specs.
- Socket set and ratchet (metric sizes, extensions)
- Description: Common sockets (10–24 mm), ratchet, extensions.
- Why: Remove bolts/nuts on air springs, compressor, brackets.
- How to use: Select correct socket, use extensions for confined spaces, use breaker bar for stuck fasteners.
- Penetrating oil (e.g., PB Blaster, WD-40 Specialist)
- Description: Spray that loosens rusted bolts.
- Why: Many WJ suspension bolts seize; penetrating oil reduces chance of breaking studs/bolts.
- How to use: Spray, wait 10–15 minutes, then attempt to loosen bolts.
- Pliers (needle-nose and slip-joint)
- Description: Hand pliers for removing clips and hoses.
- Why: Remove retaining clips from lines and connectors.
- How to use: Grip and pull clips or pinch to compress tabs and remove.
- Flathead & Phillips screwdrivers, pick set
- Description: Small hand tools for clips, clamps and headphone-style fittings.
- Why: Helpful for removing plastic clips and prying fittings.
- How to use: Use gently to avoid breaking plastic.
- Utility knife or hose cutter
- Description: Sharp cutting tool.
- Why: Trim damaged air line or cut new tubing cleanly.
- How to use: Cut squarely; use steady pressure and keep fingers away.
- Air line fittings or quick-connect push-fit couplers (pneumatic-rated)
- Description: Replacement connectors for 1/4–3/8" airline sizes (verify fit for Jeep).
- Why: Replace damaged airline segments or fittings; avoids air leaks.
- How to use: Insert tubing fully into push-fit fitting until it seats; test by tugging.
- Soapy water in spray bottle (leak detector)
- Description: Water with dish soap to locate leaks by bubbling.
- Why: Easiest leak detection method for air springs, lines and fittings.
- How to use: Spray components while compressor cycles; bubbles indicate leaks.
- Multimeter (digital)
- Description: Measures voltage, continuity and resistance.
- Why: Test power to compressor, sensors and relays.
- How to use: Set to DC volts to check 12V at connector; continuity/resistance for sensors per service specs.
- Clamp meter (optional but useful)
- Description: Measures current draw without disconnecting wires.
- Why: Test compressor current draw to tell if it’s struggling or shorted.
- How to use: Clamp around compressor power wire while compressor runs; compare to spec.
- Small mirror and flashlight/inspection light
- Description: Illuminates and helps view tight spaces.
- Why: See fittings, connectors and leaks under vehicle.
- How to use: Use mirror to view behind components; light to illuminate work area.
- Wire brushes and rags
- Description: Clean corrosion and dirt.
- Why: Clean mating surfaces, connectors, and threads before reassembly.
- How to use: Brush lightly and wipe with rags; avoid metal filings entering lines.
- Replacement parts on hand (see parts list below)
- Description: The specific parts you plan to replace (bag, compressor, fittings, sensor).
- Why: Some jobs require part swaps; having them ready speeds repair.
- How to use: Follow the replacement steps below.

- Extra / specialty tools (why they may be required)
- Small air compressor or low-pressure shop air (optional)
- Why: Helpful for blowing out lines and confirming system pressurizes after repair.
- Vacuum/pressure hand pump with gauge
- Why: Useful to precisely pressurize a bag or line to test for leaks without using vehicle compressor.
- OBD-II scanner with ABS/air-suspension module read capability (optional but recommended)
- Why: Read fault codes from suspension module (if equipped) to pinpoint sensor/valve/compressor errors.
- Impact wrench (optional)
- Why: Speeds removal of lug nuts and some stubborn bolts; not required for beginners but helpful.
- Injector/line disconnect tool set (if Jeep uses quick-disconnect fittings)
- Why: Some air line fittings use locking collars requiring a disconnect tool.

- Common failure points and what to check first (diagnosis)
- Visual inspection
- Look for cracked/dry-rotted air springs (rubber bags), frayed or pinched air lines, broken clips, rusted fittings.
- Listen for compressor
- Turn key to ON and watch/listen: compressor should run for a short time after doors closed or vehicle turned on. No sound may indicate fuse/relay/compressor failure.
- Leak detection with soapy water
- Spray around air spring seams, airline connections, Schrader-type fittings, and the valve block. Bubbles = leak.
- Height sensors and linkages
- Inspect front and rear height sensors for broken rods, seized pivots or disconnected ball studs.
- Electrical checks
- Check compressor fuse and relay, test for 12V at compressor connector with multimeter when system requests pressure, test sensor continuity.
- Compressor current draw (if you have clamp meter)
- A compressor that draws excessive amps may be failing internally or working against a large leak.

- Typical repairs and step-by-step actions (keep to basic safe methods for a beginner)
- Replace a leaking air spring (common repair)
- What it fixes: Torn/cracked bag causing slow or immediate sagging.
- Parts usually needed: replacement air spring (OEM or aftermarket), new O-ring or push-fit connector if damaged, possible new mounting hardware if corroded.
- Steps:
- Support vehicle on jack stands and chock wheels.
- Remove wheel for working room.
- Use soapy water to confirm bag leak.
- Deflate air spring by loosening the air line fitting or using vehicle controls (disconnect battery first if fiddling electrical).
- Support axle with a jack under the axle housing (use wood block to protect).
- Remove retaining bolts/nuts on top and bottom mounts (spray penetrating oil first).
- Remove old bag; clean mounting surfaces and replace any rusted hardware.
- Install new bag fully into top mount, align bottom, tighten nuts to snug and then torque to factory spec.
- Reconnect air line (replace push-fit fitting or O-ring if worn).
- Lower axle enough so bag is lightly seated, remount wheel, lower vehicle, torque lug nuts with torque wrench to spec.
- Reconnect battery and cycle system to let compressor pressurize; check for leaks with soapy water.
- Replace the air compressor
- What it fixes: Compressor that won’t run, runs constantly, or cannot achieve pressure.
- Parts usually needed: replacement compressor (and often the dryer/accumulator and mounting gasket), new relay/fuse if suspect.
- Why replace: Internal failure, burned motor, or seized internal components are common failures.
- Steps:
- Locate compressor (usually front passenger side wheel well or under right fender on WJ).
- Disconnect negative battery.
- Remove splash shield or wheel to access.
- Disconnect electrical connector and airline(s) from compressor (catch any accumulated moisture).
- Unbolt compressor mounting bolts (penetrating oil if seized).
- Remove compressor assembly; inspect/dry reservoir/drier — replace drier if contaminated.
- Install new compressor, reconnect lines and connector, ensure proper gasket/seal.
- Reconnect battery, start vehicle and let compressor run to build pressure; check for leaks.
- If compressor cycles rapidly, suspect leak elsewhere.
- Repair or replace air line / fittings
- What it fixes: Leaky or damaged plastic airline.
- Parts usually needed: replacement airline segment (correct diameter), push-fit fittings or barbed fittings and clamps.
- Steps:
- Locate leaking segment by soapy water.
- Cut out damaged section with a clean square cut.
- Install a push-fit connector or insert end into proper fitting; double-check seating.
- Spray with soapy water and cycle to verify no leak.
- Replace height sensor/linkage
- What it fixes: Incorrect height reading causing compressor to cycle or ride height issues.
- Parts usually needed: new height sensor or replacement linkage ball stud.
- Steps:
- Inspect sensor arm and link; if bent/broken, remove retaining clip or bolt and replace.
- Reconnect and make sure pivot moves freely; cycle system to verify proper operation.
- Valve block/solenoid replacement (less common)
- What it fixes: One-corner sagging when solenoid is stuck open or does not seal.
- Parts usually needed: replacement valve block or solenoid pack, or rebuild kit.
- Steps:
- Locate valve block (usually with compressor/reservoir).
- Check for leaks and electrical function; replace if a solenoid is stuck open or leaking.
- Reconnect and test.

- How to use specific tools in these tasks (short primers)
- Multimeter
- Use DC volts range: probe battery to verify 12.6V at rest. Probe compressor connector while someone triggers system (or turn key) to see if 12V arrives.
- Use continuity/ohms to check sensor circuits (compare to spec or confirm open/short).
- Soapy water spray
- Spray suspected areas and watch for steady bubble formation; wipe off residue after testing.
- Torque wrench
- Set to manufacturer torque (if unknown, use conservative values for small hardware and consult manual). Tighten until click; do not use as breaker bar.
- Floor jack and jack stands
- Lift at recommended point, place stands on flat surface, lower onto stands gently, then rock the vehicle slightly to verify stability.

- Parts that are commonly replaced and why
- Air springs (bags)
- Why: Rubber ages, cracks, or develops seam leaks—most common cause of sagging.
- Compressor
- Why: Fails electrically or mechanically, often from working too hard trying to supply a leaking system or from water ingestion.
- Accumulator/drier (moisture trap)
- Why: Prevents moisture from entering system; commonly replaced with compressor to prolong life.
- Air lines and fittings
- Why: Plastic lines can get chafed, cut or cracked and will leak air.
- Valve block / solenoids
- Why: Solenoids can stick or leak causing one-corner issues.
- Height sensors and linkages
- Why: Mechanical linkages can break or pivot seize, providing incorrect height signals.
- Relays / fuses
- Why: Electrical faults can mimic compressor or sensor failure; cheap to replace and should be checked early.

- Testing and verification after repair
- Check for leaks with soapy water while compressor runs/cycles.
- Use multimeter to ensure compressor gets and maintains 12V when commanded.
- Cycle vehicle through all ride heights and watch for correct behavior.
- Road test with normal loads and observe ride height and compressor behavior.
- Clear any stored fault codes with an OBD-II tool if you replaced parts that feed the suspension module.

- Tips and cautions specific to Jeep WJ/WG air suspension
- Replace both sides or pairs where reasonable: if one air spring on an axle has failed and the other side is old, swap the pair to avoid premature asymmetric failure.
- When replacing compressor, consider replacing the dryer; moisture is a frequent enemy of these systems.
- Don’t let the compressor run continuously for long — that’s a sign of a leak or failed component and it can overheat.
- Keep replacement parts matched to the WJ year and option code (air suspension option); verify part numbers before buying.

- Final note (short)
- If you don’t have safe lifting equipment or the job requires removing rusted bolts that you can’t safely extract, get professional help. Air suspension repairs can be handled by a competent DIYer with the tools above, but safety and correct torqueing/assembly are critical.
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