🔧 Ascent - Timing Chain Replacement

Your Ascent doesn’t have a timing belt. Its 2.4L turbo FA24 engine uses two timing chains, and Subaru doesn’t specify routine mileage-based replacement. They’re replaced only after diagnosis finds chain stretch, damaged guides, tensioner trouble, incorrect cam timing, or internal engine damage.

This isn’t a sensible first-time DIY repair. Subaru’s procedure involves extensive engine disassembly, precise camshaft positioning, liquid-gasket application, and special precautions for the variable camshaft sprockets. Subaru issued Service Bulletin 02-188-21 specifically adding a cam-sprocket check during FA/FB timing-chain work. static.nhtsa.gov

Difficulty Level: Advanced | Estimated Time: 16-25 hours

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⚠️ Safety & Precautions

• ⚠️ Disconnect the negative battery terminal before removing engine wiring, the starter, or fuel-system components.
• ⚠️ Let the engine and turbocharger cool completely before beginning.
• ⚠️ Relieve fuel pressure before disconnecting any fuel line.
• ⚠️ Support the engine only from approved lifting points with a properly rated engine hoist.
• ⚠️ Never rotate the crankshaft with a timing chain removed unless the factory procedure specifically directs it.
• ⚠️ Incorrect cam timing can allow the pistons and valves to collide, causing major engine damage.
• ⚠️ The cam sprockets contain internal locking mechanisms that must be checked before chain installation. Subaru identifies this as a professional-level service precaution. static.nhtsa.gov
• ⚠️ Use current Subaru service information for every torque, tightening sequence, sealant location, and timing-mark illustration.

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🔧 Required Tools

You'll need the following tools for this repair:

• Metric socket set, 8mm-22mm
• Metric wrench set, 8mm-22mm
• 3/8-inch drive ratchet
• 1/2-inch drive breaker bar
• 1/4-inch drive torque wrench, 2-25 Nm
• 3/8-inch drive torque wrench, 10-100 Nm
• 1/2-inch drive torque wrench, 40-250 Nm
• Torque-angle gauge
• Crankshaft pulley holding tool (specialty)
• FA-series timing-cover separator (specialty)
• Engine hoist rated 1-ton minimum
• Engine stand rated 1,000-pound minimum
• Engine lifting chains rated 1-ton minimum
• Floor jack rated 3-ton minimum
• Jack stands rated 3-ton minimum
• Wheel chocks
• Low-profile oil drain pan, 15-quart minimum
• Coolant drain pan, 15-quart minimum
• Fuel-line disconnect tool set
• Hose-clamp pliers
• Plastic gasket scraper
• 3mm liquid-gasket applicator nozzle
• Feeler-gauge set, 0.02mm-1.00mm
• Paint-marker set
• Magnetic parts trays
• OBD-II bidirectional scan tool (specialty)
• Safety glasses
• Nitrile mechanic gloves
• ABC fire extinguisher, 5-pound minimum

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Complete engine timing-chain kit - Qty: 1
• Right timing-chain tensioner - Qty: 1 if not included
• Left timing-chain tensioner - Qty: 1 if not included
• Timing-chain guides and tensioner guides - Replace as a complete set
• Front crankshaft oil seal - Qty: 1
• Timing-cover O-rings - Qty: 1 complete set
• Subaru-approved timing-cover liquid gasket - Qty: 2 tubes
• Camshaft sprocket bolts - Qty: As required by service information
• Crankshaft pulley bolt - Qty: 1 if specified as non-reusable
• Turbocharger and exhaust gaskets - Qty: 1 complete set
• Engine oil of specified viscosity - Qty: Full refill
• Engine oil filter - Qty: 1
• Subaru-compatible coolant - Qty: Full refill

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📋 Before You Begin

• Park your Ascent on solid, level ground. Apply the parking brake and chock the rear wheels.
• Scan every control module and save the trouble codes before disconnecting the battery.
• Confirm that diagnosis actually points to mechanical timing. Camshaft timing codes can also result from oil pressure, oil-control solenoids, wiring, sprockets, or restricted oil passages.
• Obtain the current Subaru service procedure for Mechanical > H4DO Turbo > Timing Chain Assembly.
• Review Subaru Service Bulletin 02-188-21 before touching the chains or cam sprockets. static.nhtsa.gov
• Photograph every hose, connector, ground wire, heat shield, and bracket before removal.
• Clear enough bench space to keep left-side and right-side timing parts completely separated.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Verify that timing-chain removal is justified

• Use the OBD-II bidirectional scan tool to record camshaft timing codes and live intake/exhaust cam-angle data.
• Check engine-oil level, condition, pressure, and maintenance history before condemning the chains.
• Inspect the oil-control solenoids and related wiring according to Subaru diagnostics.
• Do not replace the chains solely because of mileage or a brief cold-start noise.

Step 2: Disconnect and prepare the vehicle

• Use the 10mm socket to disconnect the negative battery terminal.
• Relieve fuel pressure using the procedure in the Subaru service information.
• Raise the vehicle with the 3-ton floor jack and support it securely on the 3-ton jack stands.
• Drain the oil into the 15-quart oil drain pan and coolant into the separate 15-quart coolant drain pan.

Step 3: Remove components blocking engine removal

• Use the 8mm-22mm socket set, hose-clamp pliers, and fuel-line disconnect tools to remove the intake, intercooler connections, cooling hoses, exhaust connections, wiring, grounds, and engine accessories specified by Subaru.
• Label every connector and hose with the paint-marker set.
• Keep turbocharger oil and coolant openings capped against dirt.

Step 4: Remove the engine assembly

• Attach the 1-ton lifting chains only to the approved engine lifting points.
• Support the engine with the 1-ton engine hoist.
• Use the metric socket and wrench sets to remove engine-mount and bellhousing fasteners in the factory sequence.
• Separate and lift the engine slowly while watching for hidden connectors, hoses, and grounds.
• Mount the engine securely to the 1,000-pound engine stand.

Step 5: Remove the front timing cover

• Use the crankshaft pulley holding tool and 1/2-inch breaker bar to remove the crankshaft pulley bolt.
• Remove the pulley and all front-cover fasteners with the correctly sized metric sockets.
• Record each bolt’s position because the cover uses different bolt lengths.
• Use the FA-series timing-cover separator at the approved points. Don’t pry between sealing surfaces.
• Keep sealant debris out of the oil passages and exposed engine.

Step 6: Position and inspect the timing system

• Use the crankshaft pulley holding tool to rotate the crankshaft only in the normal direction.
• Position the crankshaft and camshafts exactly as shown in the Subaru timing-chain procedure.
• Check the cam-sprocket locking condition required by Service Bulletin 02-188-21 before removing tension. static.nhtsa.gov
• Mark left and right components with the paint markers.
• Inspect the chains, guides, tensioners, sprockets, oil passages, and front cover for wear or contamination.

Step 7: Remove the timing chains

• Use the appropriate metric socket to retract and pin each hydraulic tensioner according to Subaru’s sequence.
• Remove the tensioners, tensioner guides, fixed guides, and chains in the published order.
• Do not let either camshaft snap forward under valve-spring pressure.
• Do not rotate the crankshaft or camshafts independently after chain removal.

Step 8: Install the new timing components

• Lubricate the new chains, guides, and tensioner contact surfaces with clean engine oil.
• Match every colored chain link to the crankshaft and camshaft timing marks shown in the service procedure.
• Install each guide and tensioner with the correct metric socket.
• Tighten every fastener with the correctly ranged torque wrench to the exact Subaru specification for its location.
• Recheck all timing marks before pulling either tensioner retaining pin.
• Check the marks twice. Repairs are cheaper before startup.

Step 9: Verify mechanical timing

• Use the crankshaft pulley holding tool to rotate the crankshaft slowly through two complete revolutions.
• Stop immediately if the engine binds. Never force it with the breaker bar.
• Return the crankshaft to the specified checking position and confirm the sprocket timing marks align.
• The colored chain links may not realign after rotation. Check the fixed sprocket marks as Subaru directs.

Step 10: Seal and install the timing cover

• Use the plastic gasket scraper to remove old sealant without gouging the aluminum surfaces.
• Clean and dry every sealing surface and bolt hole.
• Install new O-rings and the front crankshaft seal.
• Use the 3mm liquid-gasket applicator nozzle to apply only the specified bead size and pattern.
• Fit the cover within the sealant’s published assembly time.
• Use the torque wrenches to tighten cover bolts in Subaru’s sequence and to their location-specific specifications.

Step 11: Reinstall the engine

• Use the engine hoist and lifting chains to lower the engine into position.
• Reconnect the transmission, mounts, exhaust, turbocharger plumbing, fuel lines, cooling hoses, wiring, and grounds.
• Use new exhaust and turbocharger gaskets wherever a joint was opened.
• Torque every structural, exhaust, fuel-system, and engine-mount fastener using current Subaru service information.

Step 12: Refill and perform the first start

• Install a new oil filter and refill the engine with the specified oil.
• Refill and bleed the cooling system with Subaru-compatible coolant.
• Crank the engine without starting as directed by Subaru to establish oil pressure.
• Reconnect the ignition or fuel system and start the engine.
• Shut it down immediately if the oil-pressure warning remains on, the chain rattles continuously, or a fluid leak appears.

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✅ After Repair

• Use the OBD-II bidirectional scan tool to clear codes and inspect actual versus commanded camshaft angles.
• Check the timing cover, turbocharger lines, cooling hoses, fuel connections, and exhaust joints for leaks.
• Allow the cooling fans to cycle and verify stable coolant temperature.
• Confirm the heater produces steady heat, then recheck coolant after the engine cools completely.
• Road-test gently while monitoring oil pressure, coolant temperature, misfire counts, and cam timing.
• Recheck oil and coolant levels after the road test.

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💰 DIY vs Shop Cost

Shop Cost: $3,500-$6,500 (parts + labor)

DIY Cost: $700-$1,700 (parts, fluids, sealants, and commonly needed specialty tools)

You Save: $1,800-$5,000 by doing it yourself!

Specialist labor rates and local pricing vary considerably. This repair can occupy a professional technician for approximately 16-25 hours.

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🎯 Ready to get started?

The timing-chain aisle is open beside this guide, but don’t order parts until mechanical timing has been properly diagnosed. On your Ascent, this is closer to an engine-build operation than routine belt maintenance. HowToo makes it easy with matching timing components, tools, and specialty equipment for the job.