Buyer Research

2021 Hyundai Sonata — Should You Buy One?

Typical asking price: $14,000–$21,000. There are 3 high-severity known issues you need to know before handing over a check.

Deciding between model years? Compare the 16 Hyundai Sonata years we've written up →

Kestrel Take

Second year of the eighth-generation Sonata, and the record is more serious than its 130 complaints suggest, because four recalls sit behind them and one of them is about the fuel tank melting. The engine, fuel system and transmission clusters together are 70% of the filings — owners describe losing power on the road, a strong fuel smell, and coolant vanishing with no warning light. None of this is yet the Theta II disaster of the 2011–2019 cars, and the standard 2.5L with the conventional eight-speed is the calmer choice. Buy one only after the NHTSA VIN lookup shows the fuel check-valve recall actually performed — not just notified — and after a cold start with the hood up and the coolant reservoir checked. Second owners get a 5-year/60,000-mile powertrain warranty, not the 10/100 the original owner had; ask the dealer where this VIN stands.

What we checked

Reconciled against public records, 2026-09-25

NHTSA holds 130 owner complaints for the 2021 Hyundai Sonata, and 4 recall campaigns.

A big number here usually means a lot of these were sold, not that it is a bad vehicle — popular models collect more complaints for the same rate of trouble. So the total on its own says little. What is worth reading is the shape of it. The largest single group is the engine at 27%. That is notable without being overwhelming — worth checking, not worth panicking about.

4 recall campaigns cover this model year. Recalls are repaired free, for any owner, with no time limit on most safety campaigns — but only if someone books it in. Ask the seller to show it was done, or have any dealer check the VIN; it takes them a couple of minutes and costs nothing.

Counts come from the NHTSA complaint and recall database — free, public, and worth checking yourself.

Known Issues for the 2021 Hyundai Sonata

Ranked by wallet impact. These are documented, recurring problems — not freak accidents. How we decide that.

Fuel tank check valve can let the tank swell against the exhaust and melt (recall 25V796)High — wallet impact

Recall 25V796 covers 2020–2023 Sonatas: a damaged check valve lets air into the fuel tank, the tank expands, touches hot exhaust parts and melts, and a melted tank leaks fuel. Owners filed while parts were still unavailable in late 2025 and early 2026 — one was quoted $1,600 to replace the fuel assembly out of pocket while waiting. Others in this cluster describe a strong raw-fuel smell in the cabin, a popping sound and the engine cutting out. The 2.5L turbo cars also carry 21V524 for a high-pressure fuel pipe that can leak at the fuel-rail connection. On the VIN lookup, confirm both show as completed, not open. At the car: smell for fuel around the rear seat and under the trunk floor, and look for a fuel-level reading that drops faster than the miles explain.

Repair cost: $0 with the recall — verify it was performed; $1,200–$2,000 for a fuel tank assembly if you cannot wait for parts

Source: NHTSA complaints filed under the fuel system (32); 4 NHTSA recall campaigns on this model year.

2.5L Smartstream loses power into limp mode, knocks in park, or quietly loses its coolantHigh — wallet impact

The engine cluster is 27% of the record and it splits three ways. Owners describe the car dropping into limp mode at speed with no dash warning; a knock from the 2.5L GDI/MPI at idle that dealers call normal and then a hesitation on acceleration; and coolant disappearing with no puddle and no temperature warning — in two filings the internal core of the exhaust heat recovery system failed and dumped gallons of coolant into the exhaust. A misfire is ignition coils or injectors and costs hundreds; a coolant-into-exhaust failure or a spun engine is a four-figure job once the powertrain warranty has lapsed for a second owner. At the car: cold start with the hood up, listen for a knock that fades as it warms, check the reservoir is at the line, and pull the oil cap to look for milky residue.

Repair cost (estimate): $250–$1,200 for coils, injectors or a purge valve; $2,000–$3,500 for an exhaust heat recovery unit; $6,000–$9,000 for a replacement engine — around 51% of what this car is typically worth

Source: NHTSA complaints filed under the engine (35).

Transmission oil pump fault can kill the fail-safe mode and leave you with no drive (recall 22V746)High — wallet impact

Recall 22V746 covers 2021–2022 Sonatas with the eight-speed wet dual-clutch (the 2.5L turbo N Line): if the transmission oil pump fails, the limited-mobility fail-safe that should let you crawl to the shoulder can fail too, so the car simply stops driving. The remedy is a software update plus inspection and transmission replacement where needed. Owners in this cluster describe grinding, whining, delayed shifts, jerking and a burning smell through the vents; a few on the standard eight-speed automatic report losing power at 30 mph and coasting to a stop, then the car restarting and behaving normally. Check the recall status on the VIN, then drive it in stop-and-go traffic: a DCT that shudders or clunks on the 1–2 shift is not one to buy.

Repair cost: $0 with the recall — verify it was performed; $4,000–$7,000 for a dual-clutch transmission replacement — about 40% of what this car is typically worth

Source: NHTSA complaints filed under the transmission and drivetrain (23); 4 NHTSA recall campaigns on this model year.

Windshield may not have been bonded properly at the factory (recall) and cracks on its ownMedium

One of the four recalls on this car is for the windshield: on some 2021 Sonatas it was not properly bonded during assembly and could detach in a crash. Dealers remove and reinstall it free. The visibility cluster otherwise reads as windshields cracking from the edge without an impact and wipers or rain sensors misbehaving. Run your finger around the glass edge for an even bead of urethane, and check the recall is closed on the VIN — a new windshield with the driver-assist camera recalibrated is a real bill if you pay it yourself.

Repair cost: $0 with the recall — verify it was performed; $500–$1,100 for a windshield with camera recalibration

Source: NHTSA complaints filed under glass, wipers and mirrors (12); 4 NHTSA recall campaigns on this model year.

Forward collision avoidance brakes for nothing, or does not brake at allMedium

Nine complaints, two of them crashes: the forward collision-avoidance system slamming the brakes on an empty road, or failing to react when it should have. Hyundai has issued software updates for the radar and camera logic on this generation; a dealer can check whether this car has the latest calibration. Nothing to repair in the usual sense, but on the test drive note whether the system throws warnings when a car in the next lane drifts near, and whether the FCA warning light stays on after start-up.

Repair cost (estimate): $0–$300 for a software update or camera recalibration; $900–$1,800 for a radar module

Source: NHTSA complaints filed under the driver-assist and automatic braking systems (9).

Walk-Away Red Flags

✗Raw fuel smell near the rear seat or under the trunk floor
✗NHTSA VIN lookup shows 25V796 as remedy not yet available, or open
✗Knock at idle on a cold start that the seller calls normal
✗Coolant reservoir below the line with no visible leak under the car
✗DCT (N Line) that shudders or clunks in stop-and-go traffic
✗Burning smell through the vents after a hard drive

Good Signs

✓All four recalls shown complete on the NHTSA VIN lookup, with the dealer work order
✓Coolant at the full line on a cold engine and the same after the test drive
✓Smooth pull from 0 to 45 mph with no hesitation or knock from the 2.5L
✓Ignition coils or injectors replaced under warranty, with the invoice
✓Hyundai dealer service records through 36,000 miles