🔧 Flex - Timing Belt Replacement

Your Flex’s 3.5L V6 does not use a timing belt—it uses a timing chain (internal, oil-lubricated). There is no scheduled “timing belt replacement” service; timing chain service is only done if there’s a problem (rattle on startup, cam/crank correlation codes, guide/tensioner failure, oil sludge damage).

Assumption: You meant timing chain replacement due to a symptom or diagnosis.

Difficulty Level: Advanced | Estimated Time: 8-14 hours

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⚠️ Safety & Precautions

• ⚠️ Let the engine cool fully before draining coolant or working near the radiator.
• ⚠️ Support the engine before removing the right-side engine mount.
• ⚠️ Keep fingers clear when lowering/raising the engine with a support bar or jack.
• ⚠️ Disconnect the negative battery cable to prevent accidental cranking.
• ⚠️ Do not rotate the engine with timing components removed.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• Floor jack (rated 3-ton minimum)
• Jack stands (rated 3-ton minimum)
• Wheel chocks
• Drain pan (at least 10-quart)
• Socket set 8mm-21mm
• Deep socket set 8mm-21mm
• Wrench set 8mm-21mm
• Breaker bar 1/2-inch drive
• Torque wrench 10-150 ft-lbs
• Torque angle gauge (specialty)
• Serpentine belt tool 3/8-inch drive
• Harmonic balancer puller kit (specialty)
• Camshaft timing holding/locking tool kit for Ford 3.5L (specialty)
• Crankshaft holding tool for Ford 3.5L (specialty)
• Engine support bar (specialty)
• Trim clip remover
• Plastic razor scraper
• RTV sealant applicator nozzle
• Shop rags
• Funnel

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Timing chain kit - Qty: 1
• Timing chain tensioners - Qty: 1 set
• Timing chain guides - Qty: 1 set
• Front timing cover gasket set - Qty: 1
• Front crankshaft seal - Qty: 1
• Valve cover gasket set - Qty: 1
• Crankshaft pulley bolt - Qty: 1
• Engine coolant - Qty: 2-3 gallons
• Engine oil - Qty: 6 quarts
• Oil filter - Qty: 1
• RTV silicone gasket maker - Qty: 1

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📋 Before You Begin

• Park on level ground, set the parking brake, and chock the rear wheels.
• Disconnect the battery using a 10mm socket on the negative terminal and isolate the cable.
• Lift the front safely with a floor jack and support with jack stands at the proper lift points.
• Plan for cleanliness: timing work hates dirt. Keep shop rags handy and cap open hoses.
• Take photos before removing brackets and connectors.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Drain coolant and remove lower access

• Place a drain pan (at least 10-quart) under the radiator drain.
• Open the drain and remove the coolant reservoir cap to help it flow.
• Remove any lower splash shield/undertray fasteners using a trim clip remover and socket set 8mm-10mm.

Step 2: Remove the intake ducting for access

• Loosen intake clamps using a socket set 8mm and remove the intake tube/air ducting.
• Set parts aside so nothing falls into the throttle body opening.

Step 3: Remove the serpentine belt and front accessory brackets

• Relieve belt tension using a serpentine belt tool 3/8-inch drive and slide the belt off.
• Remove accessory/bracket bolts with a socket set 10mm-15mm.
• Keep bolts grouped by component (bags + labels helps a lot).

Step 4: Support the engine and remove the right engine mount

• Install an engine support bar (specialty) across the strut towers and take the engine’s weight.
• Remove the right-side mount and bracket bolts using a socket set 15mm-21mm.
• Torque: Mount fasteners are critical—Torque to factory specification.

Step 5: Remove valve covers (needed for cam timing tools)

• Disconnect coils/connectors as needed and remove valve cover bolts using a socket set 8mm-10mm.
• Remove both valve covers carefully so you don’t tear sealing surfaces.
• Replace gaskets during reassembly (do not reuse flattened gaskets).

Step 6: Set cylinder #1 to Top Dead Center (TDC)

• Rotate the crankshaft clockwise using a breaker bar 1/2-inch drive and the appropriate socket on the crank bolt.
• Stop at TDC as specified for the Ford 3.5L timing procedure.
• Install the camshaft timing holding/locking tool kit for Ford 3.5L (specialty). This tool holds the camshafts in the exact position so timing doesn’t slip.
• Install the crankshaft holding tool for Ford 3.5L (specialty) to keep the crank from moving.

Step 7: Remove the crank pulley (harmonic balancer)

• Remove the crank bolt using a breaker bar 1/2-inch drive and correct socket.
• Use a harmonic balancer puller kit (specialty) to pull the pulley straight off.
• Do not pry on the timing cover sealing surfaces.

Step 8: Remove the front timing cover

• Remove timing cover bolts using a socket set 8mm-13mm.
• Carefully break the RTV seal and remove the cover.
• Clean old sealant with a plastic razor scraper and shop rags.

Step 9: Remove the timing chains, guides, and tensioners

• Verify timing marks/colored links alignment before disassembly (take clear photos).
• Remove tensioners and guides using a socket set 8mm-10mm.
• Remove the chain(s) carefully while the cams remain locked.

Step 10: Install new guides, tensioners, and timing chain(s)

• Install new guides using a socket set 8mm-10mm.
• Install the new chain(s), aligning colored links to timing marks exactly.
• Install new tensioners with a socket set and release them per kit instructions.
• Torque: Timing hardware is critical—Torque to factory specification.

Step 11: Verify timing by hand rotation

• Remove the cam/crank holding tools.
• Rotate the engine clockwise by hand two full revolutions using a breaker bar 1/2-inch drive.
• Reinstall the locking tools and confirm timing alignment returns correctly.
• If it binds, stop and recheck timing.

Step 12: Reinstall front cover with new seal and RTV

• Install a new front crank seal if your kit includes it.
• Apply RTV silicone gasket maker at the specified joints and install the timing cover.
• Tighten bolts evenly using a torque wrench 10-150 ft-lbs.
• Torque: Torque to factory specification.

Step 13: Reinstall crank pulley and install a new crank bolt

• Install the pulley fully seated.
• Install a new crankshaft pulley bolt and tighten using a torque wrench plus torque angle gauge (specialty).
• Torque: This is torque-to-yield on many Ford engines—Torque to factory specification.

Step 14: Reassemble valve covers, engine mount, accessories, and belt

• Install valve covers with new gaskets using a socket set 8mm-10mm.
• Torque: Torque to factory specification.
• Reinstall the right engine mount/bracket using a socket set 15mm-21mm, then remove the engine support bar.
• Reinstall brackets and accessories using a socket set 10mm-15mm.
• Reinstall the serpentine belt using a serpentine belt tool 3/8-inch drive.

Step 15: Refill fluids

• Refill cooling system using a funnel and the correct engine coolant.
• Change oil and filter (coolant/oil contamination risk during timing cover work).

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✅ After Repair

• Reconnect the battery using a 10mm socket.
• Start the engine and listen: you want smooth idle and no chain rattle.
• Check for oil leaks at the timing cover and valve covers.
• Let it reach operating temperature and verify the heater blows hot (helps confirm coolant circulation).
• Recheck coolant level after the first drive and top off as needed.

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💰 DIY vs Shop Cost

Shop Cost: $1,800-$3,500 (parts + labor)

DIY Cost: $350-$900 (parts only)

You Save: $1,450-$2,600 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 8-14 hours.

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🎯 Ready to get started?

HowToo makes it easy: same-day/2-day shipping on every part, plus all the tools and specialty tools you need! Check out the parts and tools sections below to add everything to your cart.