A connecting rod bearing was thrown through the engine block causing it to stall out on the freeway. This is exactly what is occurring with vehicles in the Theta Class Action Settlement but the company states my VIN number is not included.
2018 Hyundai Tucson engine problems
moderate 155 complaints filed with NHTSA · avg repair $3,100 · see engine across all vehicles →
Failure mileage
Complaints
155
Recalls
0
Avg fix
$3,100
5fires
1injury
When does it fail?
Of the 155 engine complaints filed for the 2018 Hyundai Tucson, here's the actual mileage breakdown — failures cluster heaviest at 0-25,000 mi.
0-25k
25-50k
50-75k
75-100k
100-125k
125-150k
150k+
Each bar shows the share of total complaints filed at that mileage range. Peak failure window highlighted. Some owners report problems earlier; some make it well past 150,000 miles symptom-free. Maintenance habits and driving conditions shift the curve as much as mileage alone.
What stands out
Engine accounts for 41% of every owner complaint on file for this vehicle — the dominant problem area across 9 categories tracked.
Owners have filed 155 engine complaints with NHTSA against this vehicle, but no formal recall covers the issue — the federal record reflects what manufacturers have admitted, not everything owners are reporting.
The failure pattern owners describe
Buyer takeaway: The 2018 Hyundai Tucson has widespread engine problems. Excessive oil burning without early warning, sudden loss of power at highway speeds, and catastrophic rod bearing failures all occur within normal ownership periods—sometimes before 60,000 miles. Hyundai denies warranty coverage or delays repairs indefinitely while owners remain stuck with monthly payments on unsafe, non-functional vehicles.
The 2018 Hyundai Tucson engine complaints center on two broad failure patterns: excessive oil consumption and sudden loss of power while driving.
Oil consumption dominates the narratives. Owners report burning through oil at rates far exceeding normal operation—anywhere from one quart per 1,000 miles to five or six quarts per 1,000 miles. Many say they receive no warning lights until the engine is critically low or already damaged. Dealership oil consumption tests confirm the problem in multiple cases, yet Hyundai denies engine replacement warranty coverage unless owners hit specific consumption thresholds or engine damage occurs. One owner added oil every week; another had to top off daily. Dealers recommend cleaning treatments that provide only temporary relief. The lack of early warning compounds the hazard: owners maintain regular service intervals but still encounter metal shavings in the oil, burned valves, and seized engines with minimal dashboard indication.
Sudden power loss while driving creates immediate safety risks. Owners report the vehicle dropping into limp mode or losing acceleration entirely at highway speeds (55–70 mph), often with check engine lights flashing or illuminating only after the failure begins. Some vehicles recover briefly after restart; others stall completely and require towing. A few owners cite near-miss collisions when traffic-heavy highways are involved. The "knock sensor replacement" appears repeatedly as a repeated "fix" that fails to resolve the underlying issue—one service advisor explicitly told an owner the repair was "not a fix, it is a temporary thing until it shows again."
Engine failures manifest as rod bearing failures, water ingress into cylinders, metal shavings detected during inspection, and catastrophic seizure. Many occur between 56,000 and 110,000 miles. Warranty denial is common, especially once odometer mileage exceeds 100,000 miles or original ownership transfers.
Same Hyundai Tucson engine reports on nearby years: 2015 · 2016 · 2017 · 2019 · 2020
Failure modes owners describe
Excessive Oil Consumption
Engine burns oil at abnormal rates (1–6+ quarts per 1,000 miles) despite proper maintenance and no visible external leaks. No early warning lights in most cases until oil level becomes critically low or engine damage occurs. Dealership oil consumption tests confirm the defect; Hyundai denies full engine replacement coverage unless specific test thresholds are met or catastrophic failure is imminent.
When: Typically begins between 60,000–80,000 miles, worsening over time. Some owners report the problem beginning within months of purchase.
Symptoms owners cite: Oil level drops rapidly despite regular changes; No check engine or low-oil warning lights until critically low; Metal shavings or sludge found in oil; Burned or damaged spark plugs soaked in oil; Engine knock or pinging sounds; Catalytic converter clogging from oil contamination; Engine stalling or loss of power in later stages
Codes mentioned: P0087 (Fuel Rail Pressure Low), P0011 (Camshaft Position Timing Over-Advanced), P1326 (Knock Sensor Detection Faulty), P0014 (Camshaft Position Timing Over-Advanced (Exhaust))
Repairs/costs cited: Dealerships recommend engine combustion cleaning (cost ~$700 noted in one case), which provides temporary relief only. Multiple owners underwent oil consumption testing at dealership expense before denial of engine replacement. Engine replacement costs quoted at $7,600–$10,000; some owners denied coverage entirely, others charged 20% copay (~$1,800) despite passing failure tests. One case noted pre-authorization denial for new engine.
Recalls/TSBs owners mention: Hyundai Service Campaign 966 and Theta II GDI Engine Settlement mentioned by owners. Knock sensor replacements performed repeatedly under warranty or recall, but owners report the fix is temporary. Extended warranty extension to 150,000 miles noted in one complaint but later denied coverage due to 'sludge in engine' despite owner maintaining service. Corporate directive in one case instructed dealership to perform knock sensor replacement knowing it was not a permanent fix.
Sudden Loss of Power / Limp Mode at Highway Speeds
Vehicle enters limp mode or loses motive power without warning while driving at highway speeds (55–70 mph), typically accompanied by check engine light flashing or illuminating after the event. Vehicle drops to 35–60 mph and 2,000 RPM, creating dangerous speed differential in traffic. Many cases involve near-miss collisions.
When: Occurs intermittently, sometimes recurring within hours or days despite dealer repairs. Multiple incidents on same vehicle. Mileage range 46,000–110,000 miles.
Symptoms owners cite: Sudden deceleration to 35–60 mph despite accelerator input; Check engine light flashing or illuminating during/after loss of power; Engine revving with no forward response; AC system disabling (indicates engine protection event); Vehicle hesitation and jerking at stops or low speeds; Loud knocking, pinging, or pinging sounds from engine before failure; Engine stalling and failing to restart for several minutes
Codes mentioned: P0087 (Fuel Rail Pressure Low), P1326 (Knock Sensor Detection Faulty), No diagnostic codes recorded in some cases despite limp mode activation
Repairs/costs cited: Knock sensor replacement performed multiple times in same vehicles without resolving the issue. One service advisor admitted the knock sensor replacement is 'not a fix, it is a temporary thing until it shows again.' Timing chain tightening, fuel injector replacement (2 and 3 replaced in one case), and engine cleaning attempted without resolution. Loaner vehicles denied or demanded back by dealerships while vehicle remains undiagnosed.
Recalls/TSBs owners mention: Hyundai corporate directs dealerships to perform knock sensor replacement even after prior failure. No permanent repair offered in several cases. One complaint references Service Campaign 966 and Theta II GDI Engine Settlement. Corporate denies engine replacement in some limp-mode cases, claiming knock sensor replacement is the approved fix.
Rod Bearing / Connecting Rod Failure
Engine rod or connecting rod fails, punching through engine block or causing catastrophic internal damage. Accompanied by loud knocking, metal shavings in oil, and complete engine seizure. No warning lights prior to failure in most cases despite regular maintenance.
When: Occurs between 46,000 and 90,000 miles in reported cases. One owner experienced second rod failure after engine replacement 14 months earlier.
Symptoms owners cite: Loud knocking sound from engine that escalates to loud boom; Complete loss of power on highway; Black smoke or steam from engine; Engine seizes and will not restart; Metal shavings visible in oil pan or on dipstick; Oil puddling under vehicle; No check engine light prior to failure
Codes mentioned: No diagnostic codes recorded in most cases prior to failure
Repairs/costs cited: Engine replacement required; costs cited as $6,000–$10,000 including labor. One owner replaced engine once, installed used Theta engine, and experienced rod failure again 14 months later. Hyundai refuses to cover either replacement under warranty.
Recalls/TSBs owners mention: Hyundai denies warranty coverage for rod bearing failures in most cases, citing warranty expiration or mileage limits. One owner with extended warranty noted dealership had multiple Tucsons in for identical rod bearing issue but Hyundai corporate refused coverage. Some rod bearing failures occur within warranty period but denial persists.
Engine Overheating / Thermal Shutdown (Water Ingress)
Water or coolant enters engine cylinders, causing overheating, loss of compression, and engine seizure. One case diagnosed water in oil; another references piston connecting rod punching through engine block with mix of antifreeze and oil observed. No warning before catastrophic failure.
When: Occurs during highway driving; one case at approximately 78,000 miles.
Symptoms owners cite: Loss of motive power while driving; Ticking sound escalating to loud knocking; Engine revving with no forward acceleration; Vehicle losing power and stalling; No warning lights illuminated prior to failure; Antifreeze and oil dripping behind engine; Engine seized, no compression
Codes mentioned: NHTSA Campaign Number: 21V727000 (Engine) referenced in one case
Repairs/costs cited: Engine replacement required. One owner's independent mechanic diagnosed water ingress; dealership later submitted to Hyundai Corporate for review but repair status unclear.
Recalls/TSBs owners mention: One case submitted to Hyundai Corporate; repair outcome not stated in narrative.
Timing Chain / Camshaft Issues with KSDS Software Update
Following KSDS engine software update by Hyundai dealership, vehicle begins stalling intermittently and failing to restart for extended periods. Vehicle later stalls, and upon restart will not exceed 35 mph. Loose timing chain and exhaust camshaft identified; repair attempted but failure recurs immediately.
When: Began approximately 3 weeks after KSDS software update (update performed Jan 22, 2024; stalling began ~Feb 11, 2024). Mileage not specified.
Symptoms owners cite: Intermittent stalling with no restart for several minutes; Vehicle will not exceed 35 mph after restart; Vehicle stalls in service garage during diagnostic; No diagnostic codes recorded despite repeated failures; Issue reoccurs immediately after repair attempts
Codes mentioned: No diagnostic codes recorded during events
Repairs/costs cited: Loose timing chain and exhaust camshaft changed on 3/13/2024; issue recurred 3/14/2024. Vehicle returned 3/15/2024 and duplicated failure in service garage, had to be pushed out. Dealership drove vehicle ~200 miles in attempt to reproduce issue. No further diagnosis or permanent repair made.
Recalls/TSBs owners mention: Complaint filed with Hyundai Corporate; company attempted to convince owner to accept vehicle in unrepaired state. Owner alleges Hyundai aware of widespread issue with KSDS software update affecting multiple vehicles and is being dishonest about cause and required remedy.
Catalytic Converter Clogging / Premature Failure
Catalytic converter becomes clogged (typically from engine oil contamination due to excessive oil burning) and requires replacement, sometimes multiple times. In one case, vehicle lost power as a result. Costs exceed $8,000 in one instance.
When: Occurs in later stages of excessive oil consumption. Cited in cases between 78,000–102,000 miles; one owner had replacement 1 year 8 months prior to second failure.
Symptoms owners cite: Loss of power / inability to accelerate; Check engine light illuminated; Abnormal sounds from engine; Vehicle struggling uphill
Codes mentioned: Check engine light (specific codes not always noted)
Repairs/costs cited: Replacement costs cited as $8,000+ (estimated). In one case, catalytic converter replaced twice in ~20 months.
Recalls/TSBs owners mention: Hyundai stated catalytic converter failure not covered under active engine recall, despite owner belief failure stems from defective engine. No warranty assistance offered.
Engine Stalling with No Restart Capability
Engine stalls completely while driving or at rest and fails to restart, or requires extended wait (up to 30 minutes) before restart is possible. Some cases result in near-collisions or unsafe situations.
When: Varies; some intermittent, some recurring. Mileage range 46,000–110,000 miles.
Symptoms owners cite: Engine stalls without warning; No restart or delayed restart for minutes to half hour; Check engine light may or may not illuminate; Oil level extremely low or dry in some cases; No warning lights in advance of stall
Codes mentioned: P0087, No codes in some cases
Repairs/costs cited: Multiple repair attempts including knock sensor replacement, timing chain adjustment, fuel injector replacement without permanent resolution. One case involved loaner vehicle denial and dealership pressure to accept vehicle in unrepaired state.
Recalls/TSBs owners mention: Dealerships perform temporary fixes (knock sensor, fuel injector replacement) per corporate directive. Corporate refuses engine replacement in some cases or demands additional diagnostic testing at owner cost.
Oil Drain Plug / Oil Pan Failure
Oil drain plug falls or becomes loose after oil service, or oil pan has faulty threads and bad seals, resulting in rapid oil loss and engine failure. Low oil triggers seizure and loss of power while driving.
When: One case documented ~4 months after oil change service; another involved bad threading on oil pan and faulty seals.
Symptoms owners cite: Oil puddling under vehicle; Complete loss of power while driving; Engine failure / seizure; Check engine light or no warning prior to failure
Codes mentioned: No codes in some cases
Repairs/costs cited: One case: drain plug had fallen after previous oil change; vehicle not repaired. Another case: oil pan bolt under-tightened due to bad threading; oil pan seals faulty. Engine seizure resulted.
Recalls/TSBs owners mention: Not addressed by manufacturer in reported cases.
Synthesized from 155 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 13 most recent
Engine (1.6-liter turbocharged direct-injection four-cylinder) had a catastrophic failure driving along highway. Engine instantly lost power and stalled. No indicators on instrument cluster prior to engine stall, temperature gauge for coolant indicating nominal conditions. Upon pulling over to the side of the road, check engine & batter indicator lights shown on the instrument cluster.…
I bought my 2018 tuscon one year ago in June 2020. 70,000 miles on it now, regular maintenance. No warning lights, everything was running OK. I started experiencing hesitation taking off then lunging when stopped in the last few months. Now I'm sitting in the driveway because it won't start. Realized oil was low which is odd because I've noticed it's been burning more than previous but no…
Emission light is on and called dealer for an appointment, stated they will called me when they can line me up with a tech and I still waiting.
My 2018 Hyundai Tucson has been experiencing oil consumption issues for over a year. It began at around 80k miles, when it should have been covered by warranty but they made me pay out of pocket for an oil consumption test only to ultimately recommend a top end cleaning, which I also paid for and it did not solve the problem. This is a known issue with Hyundai, and they have settled many…
I get oil changes quite frequently due to the mileage I put in a vehicle. I have 7 oil changes/tire rotations between november 2018 and november 2019. On november 13th 2019 my check engine like came on and at the same time my engine started making a knocking sound. Prior to this I had no indicators that anything was wrong. I immediately took it to the dealership and was informed that I need a…
Motor knocking with only 65,000 miles. Not getting power
On Saturday, November 23rd, while driving down the highway the check engine light came on and the car would not accelerate past 40 mph. When accelerating from a stop, the car's acceleration is greatly diminished. The car was checked out be a local Hyundai dealership. After running a diagnostic, the mechanic reported the following: the car has a knock sensor code, valve stem seals are leaking…
Oil consumption, will change oil and within weeks i will be down 23 Quarts of oil
This is the 2nd time I have had a sensor indicator. The first was a knock sensor where my car barely made it across the road. Now another code for intake issues. If my car dies and I get hit Hyundai is liable. I know many people that have issues with their Hyundai dying and are without their cars waiting for repairs for. months and months, but the fact that I have a grandson and my car could die…
Had engine trouble with your 2018 Hyundai Tucson?
File a complaint with NHTSA → It's free, official, and how every report above got here — owner filings are the federal safety record this page is built on.
Common questions
How serious is the engine problem on the 2018 Hyundai Tucson?
It's a documented issue but not catastrophic. 155 complaints have been filed. Repairs average $3,100 and most owners catch it before it causes a breakdown.
At what mileage does the engine typically fail?
Across the 42 complaints that reported odometer mileage, most engine failures cluster between 35,000 and 90,000 miles, with the median around 72,000. A quarter of owners report trouble before 35,000; a quarter make it past 90,000. Maintenance history matters more than the odometer alone — this is the reported failure window, not a guarantee.
What does it cost to fix?
Independent shops typically charge around $3,100 for engine repairs on this vehicle. Dealer pricing tends to run 20-40% higher. The exact figure depends on the specific failure mode, parts availability, and your local labor rates. If you're outside factory warranty, an extended service contract often covers this category.
Are there any recalls related to engine?
No active recalls currently cover engine issues on this vehicle. The complaints filed represent owner-reported failures that haven't risen to the level of a manufacturer-issued recall — but they're still worth knowing about before you buy or budget for repairs.
Related
Complaint and recall data sourced from the National Highway Traffic Safety Administration (NHTSA)
public records database. Verify the raw federal record at
nhtsa.gov/vehicle/2018/Hyundai/Tucson.
Severity ratings are derived from reported crashes, fires, injuries, and fatalities. Repair cost estimates are
independent-shop national averages and may differ in your area. Some links on this page are affiliate links.