Hyundai & Kia Theta II 2.4L Engine
The Theta II 2.4 is the engine in millions of Hyundai Sonatas, Santa Fes, Kia Optimas, Sorentos and Sportages. It is also the engine behind one of the largest recall and class action stories in recent American automotive history. If you are here because yours started knocking, this page explains exactly what happened, and — importantly — one thing to check before you spend a penny on a replacement.
Our Hyundai engines start at $770, rod-knock tested before they go on the shelf.
Hyundai engines Text your VINCheck this before you buy anything
Your car may still be covered. The Hyundai and Kia class action settlement — valued at around $1.3 billion and covering close to four million vehicles — included a lifetime warranty on these engines. It costs you nothing to check, and if your vehicle qualifies you should not be buying an engine at all.
We would rather tell you this and lose the sale than sell you an engine you did not need.
Which vehicles the settlement covered
| Vehicle | Years |
|---|---|
| Hyundai Sonata | 2011–2018, and certain 2019 |
| Hyundai Santa Fe Sport | 2013–2018, and certain 2019 |
| Hyundai Tucson | 2014–2015, 2018, and certain 2019 |
| Kia Optima | 2011–2018, and certain 2019 |
| Kia Sorento | 2012–2018, and certain 2019 |
| Kia Sportage | 2011–2018, and certain 2019 |
The vehicle must have a genuine Theta II 2.0 or 2.4 litre gasoline direct injection engine within original manufacturer specification. The 2019 models included are those built before the knock sensor detection system was fitted at the factory.
The catch: KSDS
The lifetime warranty is conditional on having the knock sensor detection system (KSDS) software update installed. It is a free update that continuously monitors the engine for the early signs of this specific failure and warns the driver before it becomes catastrophic.
No claim form is needed for the warranty itself, but the KSDS update has to be done. Call a dealer with your VIN and ask two questions: is my vehicle covered, and has the KSDS update been performed.
What actually fails
The failure is in the connecting rod bearings.
Hyundai attributed it to manufacturing: metallic debris left around the crankshaft area, which it traced to a deburring process. That debris restricted oil flow through the connecting rod bearings. Starved of oil, the bearings wear, then the rods are damaged. Kia described its own version as bearings wearing out prematurely and seizing.
What it sounds like
- A deep knocking from the bottom of the engine, loudest under load or on acceleration. This is rod knock, and it is terminal.
- Oil pressure warning light, sometimes intermittent at first.
- A metallic rattle that gets worse rather than clearing as the engine warms.
- In the worst cases the engine seizes without much warning.
If you hear rod knock, stop driving it. Continuing to run a knocking engine turns a bearing problem into a destroyed crankshaft and block, and it removes the option of a cheaper repair.
The recalls, in order
| When | What |
|---|---|
| September 2015 | About 470,000 2011–2012 Hyundai Sonatas |
| April 2017 | About 572,000 more, including 2013–2014 Sonata and Santa Fe Sport |
| 2017 (Kia) | More than 618,000 — 2011–2014 Optima, 2012–2014 Sorento, 2011–2013 Sportage |
| December 2020 | About 423,000 — the first recall to include the MPi, non-direct-injection variants |
NHTSA has investigated the timeliness and scope of the recalls, and owners filed more than 29,000 complaints. Class actions followed in both the United States and Canada.
GDI or MPi? It matters
There are two different Theta II 2.4 engines, and people use the names interchangeably when they should not.
| 2.4 MPi (G4KE) | 2.4 GDI | |
|---|---|---|
| Injection | Multi-point, port | Gasoline direct injection |
| Compression | 10.5:1 | 11.3:1 |
| Output | Around 176–177 hp | 188–203 PS depending on version |
| Recall exposure | Lower — only included from December 2020 | The main focus of the recalls and the settlement |
Both are 2,359 cc with an 88 mm bore and 97 mm stroke. They are not interchangeable: different fuel systems, different compression, different management.
How to identify your Theta II
On Hyundai and Kia the engine is identified by the 8th digit of the VIN, as on most vehicles sold in the US. That tells you the engine family.
What it does not tell you by itself is GDI versus MPi on every model year, or whether the engine in the car is still the original one. A car that already had a warranty engine fitted is a different proposition from one running its factory unit.
Text your VIN to +1 (361) 470-5276 and we will tell you which variant you need, what interchanges, and whether the year falls inside the settlement window. Free, and it takes a few minutes.
Which vehicles use the Theta II 2.4
| Hyundai | Kia |
|---|---|
| Sonata 2007–2019 | Optima 2008–2019 |
| Santa Fe 2010–2020 | Sorento 2009–2020 |
| Tucson 2010–2020 | Sportage 2010–2021 |
| Azera / Grandeur 2008–2019 | Cadenza 2009–2019 · Forte 2008–2012 · Rondo 2008–2013 |
Browse stock: used Hyundai engines · Hyundai transmissions · Kia transmissions.
Buying a used Theta II: what to ask
- Was the donor engine a replacement unit? Many Theta IIs on the market are warranty replacements with updated parts and low mileage. Those are the good ones.
- Has it been rod-knock tested? Every Theta II we list is listened to under load before it goes on the shelf, because this is the one failure that matters on this engine.
- GDI or MPi? Confirm which one your car takes before ordering. They look similar and do not swap.
- Get the KSDS update done anyway. Even on a replacement engine, the early-warning software is worth having.
- Change the oil on schedule and do not stretch it. This engine is less forgiving of long intervals than most.
Used vs remanufactured Theta II
When used makes sense
A low-mileage used Theta II — especially a warranty replacement unit — is the most cost-effective route by a wide margin, provided it has been properly tested for bearing noise. These engines are plentiful precisely because so many cars were written off around them.
When remanufactured makes sense
A rebuild with new bearings and a properly cleaned oil gallery addresses the root cause directly. If you are keeping the car long term and want the bearing question closed, it is a defensible spend. Ask specifically what was done about the oil passages, not just the bearings.
Used Theta II prices
Our Hyundai engines start at $770, with Theta II units priced by variant and mileage. Mileage on every listing is read off the donor odometer rather than estimated, and we photograph the actual unit before it ships.
Live prices: used Hyundai engines.
What is included
Engines ship as tested assemblies. You transfer your own intake, sensors, accessories and flywheel or flexplate from the old engine. Each listing states what is attached to that unit.
If the original engine failed with rod knock, check the oil cooler and lines before reusing them. Debris from a failed bearing travels.
Shipping and warranty
Every engine is compression tested and photographed on the pallet before dispatch. Preparation takes 3 to 5 business days, then 2 to 4 days in transit on insured freight. Shipping is free to any address in all 50 states, residential included.
Standard warranty is 6 months, extendable to 3 years, with 7-day returns and free return shipping. Full terms: engine warranty policy · shipping policy · returns.
Frequently asked questions
Why do Hyundai and Kia Theta II engines fail?
The failure is in the connecting rod bearings. Hyundai attributed it to metallic debris left around the crankshaft during manufacturing, traced to a deburring process, which restricted oil flow through the rod bearings. Starved of oil the bearings wear and the rods are damaged. Kia described its version as bearings wearing out prematurely and seizing.
Is my car still covered for a free engine?
Possibly. The class action settlement, valued at around $1.3 billion and covering close to four million vehicles, included a lifetime warranty on these engines. It covers 2011 to 2018 and certain 2019 Sonata, Optima, Sportage, 2013 to 2018 Santa Fe Sport, 2012 to 2018 Sorento and certain Tucson years, with a genuine Theta II 2.0 or 2.4 GDI engine. The warranty requires the free KSDS software update to have been installed. Call a dealer with your VIN before buying anything.
What is KSDS?
The knock sensor detection system. It is a free software update from Hyundai and Kia that continuously monitors the engine for the early signs of this specific bearing failure and alerts the driver before it becomes catastrophic. Installing it is a condition of the settlement's lifetime warranty.
What does Theta II rod knock sound like?
A deep knocking from the bottom of the engine, loudest under load or acceleration, often with an oil pressure warning light. Unlike a cold-start rattle it gets worse rather than clearing as the engine warms. If you hear it, stop driving the car — continuing turns a bearing failure into a destroyed crankshaft and block.
Is the 2.4 GDI the same as the 2.4 MPi?
No. Both are 2,359 cc with an 88 mm bore and 97 mm stroke, but the GDI runs direct injection at 11.3:1 compression and the MPi runs port injection at 10.5:1. Different fuel systems and management, and they do not interchange. The GDI was the main focus of the recalls; MPi variants were only included from December 2020.
Which Theta II engines were recalled?
September 2015 covered about 470,000 2011 to 2012 Sonatas. April 2017 added about 572,000 more including 2013 to 2014 Sonata and Santa Fe Sport. Kia recalled more than 618,000 covering 2011 to 2014 Optima, 2012 to 2014 Sorento and 2011 to 2013 Sportage. A further 423,000 followed in December 2020, the first to include MPi variants.
Are replacement Theta II engines any better?
Warranty replacement units generally came with updated parts and start from zero mileage, so a used engine that is itself a former warranty replacement is often the best buy on this platform. Ask whether the donor engine was original or a replacement.
How much is a used Theta II 2.4 engine?
Our Hyundai engines start at $770, with Theta II units priced by variant and mileage. Every unit is listened to under load for bearing noise before listing, and we send photos of the actual engine before it ships.
Send your VIN. We will tell you which variant fits, what we have, and whether your car might still be covered.
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