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Key points
• Interference fit is typically 0.02-0.05 mm.
• Expansion of Ø50 mm steel sprocket at 180 °C ≈ 0.11 mm – enough clearance.
• Induction heating gives fastest, most uniform expansion; no pressing force on thrust bearings.
• Absolute cleanliness and a rehearsal (“cold trial”) are critical – if the gear stops half-way it must be pulled and replaced.
Engine/part configuration
• Kia/Hyundai 1.4/1.6 L petrol Gamma (G4FA/G4FC/G4FJ) and 1.6 L diesel U-II (D4FB) use a keyless, interference-fit crank sprocket clamped by the damper bolt. Earlier Alpha/Beta engines use a Woodruff key – check the EPC/engine stamp before starting.
• Nominal outer diameter of crank nose: 35-38 mm (petrol) or 40 mm (diesel). Sprocket bore is 20-50 µm smaller.
Physics of shrink fit
Δd = α · d · ΔT
α_steel ≈ 11.7 × 10⁻⁶ /K
For d = 50 mm, ΔT = 180 K → Δd ≈ 0.105 mm; more than twice the usual interference, giving slip fit plus safety margin.
Equipment
• 3–15 kW portable induction heater, 10–30 kHz, split or removable coil ID ≈ 70 mm.
• Contact-free pyrometer or K-type thermocouple paint stick (200 °C).
• Heat-proof gloves, face shield, cotton clothing.
• Sprocket puller (three-jaw or split-plate) for removal.
• Dial indicator on magnetic stand (run-out check).
• New crank bolt and washer (single-use torque-to-yield, Hyundai/Kia P/N 23127-2B000 for petrol).
Procedure (step-by-step)
Preparation
a) Isolate battery, lock crank via service hole or flywheel tool, remove damper bolt (115 Nm + 90° petrol; 250 Nm diesel) and vibration damper.
b) Remove upper/lower timing covers, tensioner, chain, guides.
c) Clean crank snout with brake cleaner and a non-metallic scrub pad; surface must be bright metal.
d) Measure snout Ø and new sprocket bore to confirm interference (micrometer + bore gauge).
e) Shield crank seal with a damp rag or aluminium foil. Rehearse the motion of sliding the hot sprocket on in one movement.
Heating
f) Place sprocket in induction coil, 2–3 mm air-gap. Ramp power until temperature reaches 180 °C; dwell ≤ 60 s for uniformity.
g) Remove coil immediately; do not over-shoot 250 °C (blue oxide colour = overheated).
Installation (time-critical 15 s)
h) Wearing gloves, grasp sprocket with pliers or insulated tongs, align chamfer with crank nose, push fully home against the journal shoulder.
i) If hand force is insufficient, use the NEW crank bolt and thick washer to draw it the last 1-2 mm before cooling arrests movement (thread finger-tight beforehand to save seconds).
Cooling & checks
j) Let assembly air-cool. No water/oil quench.
k) Zero run-out gauge on sprocket face; reading ≤ 0.05 mm is acceptable.
l) Install timing chain, guides, tensioner (bolt 9.8-11.8 Nm), re-fit damper, and torque the crank bolt:
– Petrol: 46 Nm → 90° → 90° (or 115 Nm → 90° depending on year)
– Diesel: 250 Nm → 30°
Failure modes & remedies
• Gear stops half-way: puller + another new sprocket (never re-heat on shaft). Inspect snout for scoring.
• Overheating (> 300 °C): discard sprocket (tempered); start over.
• Insufficient expansion: verify heater rating, scale/rust on bore, wrong temperature.
| Comparison with alternatives Method |
Pros | Cons |
|---|---|---|
| Cold press | No heating kit required | 10–15 t press, crank removal, thrust bearing risk |
| Oven/hot-plate | Cheap, gentle heat | 20-30 min soak, whole gear hot (burn hazard), less localised |
| Torch | Portable | Uneven heat, oxide, temper risk |
| Induction (best) | Seconds, uniform, localised | Need induction heater, operator skill |
• OEMs increasingly delete keys to reduce stress raisers; precision shrink fits plus high-torque TTY bolts transmit up to 400 Nm reliably.
• Compact 2–6 kW handheld induction heaters (< 3 kg) are now common in European workshops; cost €800-€1200.
• Composite (two-piece) crank gears with integrated reluctor rings are entering the Hyundai/Kia K-platform – temperature limits drop to 160 °C; always consult latest TSBs.
• Induction frequency 20–30 kHz heats the 6–8 mm wall thickness most efficiently (skin depth ≈ 0.4 mm).
• A light smear of dry MoS₂ spray (< 1 µm) on crank nose can prevent galling without compromising friction fit.
• Use Tempilstik 200 °C on two opposite teeth to confirm uniform heating.
• Follow local safety at work regulations (EU Machinery Directive 2006/42/EC; OSHA 29 CFR 1910 in US).
• Dispose of overheated or cracked gears; refitting compromises engine safety and warranty.
• Use only genuine or certified aftermarket parts to avoid counterfeit risks.
• Practise the installation with a cold dummy gear first.
• Keep a spare sprocket on hand – the cost is negligible versus engine downtime.
• Photograph timing marks before chain removal to avoid indexing errors.
• Data apply to steel gears; do not heat sintered aluminium or bi-metal reluctor wheels above 120 °C.
• Some early 1.6 CRDi engines do have a shallow woodruff key; if present, alignment must be exact.
• Always replace the one-time-use crank bolt and front seal when the gear has been pulled.
• Examine ultrasonic assistance to verify interference integrity without disassembly.
• Investigate induction “pre-heat plus cryo shaft” dual method for high-precision race engines.
• Review Hyundai/Kia technical bulletin GROUP 11-EM01 for updates on crank gear fit tolerances.
Induction-heating shrink fitting is the safest, most precise way to install the interference-fit crankshaft sprocket on modern Kia Ceed engines. Heat the new gear to ~180 °C, slide it swiftly onto a scrupulously clean, cold crankshaft, let it cool, then verify run-out. Keep below 250 °C, replace the torque-to-yield crank bolt, and your timing drive will be as robust as factory-assembled.
