7 Serious Kia 2.5 Turbo Engine Problems (Hyundai, Kia, Genesis)

If you’re buying a 2020+ Hyundai Sonata, Kia Stinger, K5, Sorento or even a Genesis G70 and many other South Korean models of the said brands, chances are you’ll find the 2.5 Turbo engine sitting under its hood.

If that’s the case, you’re in the right place. We did thorough research on this engine and here’s what we found.

Doing proper research before you go and buy a car should be one of your top priorities. Especially when it comes to brands like Hyundai and Kia. Even though quite popular, their engine lineup was not regarded as very reliable in the past. Mainly because of the common problems with these engines that keep piling up. This is why we are here to help you out.

First, we are going to cover the basic specs of the two 2.5 turbo engines, then we are going to discuss the Kia 2.5 turbo engine problems and also see what are the applications of this engine. So, without further ado, let’s dive into the article.

Basic Kia 2.5 Turbo Engine Specs

The 2.5 turbo engine is part of Hyundai’s Smartstream family of internal combustion engines. If you don’t know, Kia and Hyundai are sister companies. They share everything that is installed on their models, including the engines.

So, Hyundai is designing and manufacturing these engines that are installed both on Hyundai and Kia models.

What is important to note when it comes to the 2.5 engine is that there are two different engine codes. So, let’s cover the specs of these two engines.

Smartstream G2.5T (G4KP)

  • Configuration: inline-4
  • Displacement: 2.5L
  • Cylinder Bore: 88.5 mm
  • Piston Stroke: 101.5 mm
  • Block & Head Material: Aluminum
  • Head Design: DOHC, 4 valves per cylinder
  • Compression Ratio: 10.0:1 or 10.5:1
  • Fuel Injection: Direct Injection
  • Turbocharger: Yes
  • Horsepower: 277 – 290 hp
  • Torque: 311 lb-ft (422 N-m) @ 1,650 rpm

Smartstream FR G2.5T (G4KR)

  • Configuration: inline-4
  • Displacement: 2.5L
  • Cylinder Bore: 88.5 mm
  • Piston Stroke: 101.5 mm
  • Block & Head Material: Aluminum
  • Head Design: DOHC, 4 valves per cylinder
  • Compression Ratio: 10.5:1
  • Fuel Injection: Direct Injection + MPI Injection
  • Turbocharger: Yes
  • Horsepower: 300 hp
  • Torque: 311 lb-ft (422 N-m) @ 1,650 rpm

Common Kia 2.5 Turbo Engine Problems

Common problems with the Kia 2.5 turbo engine include:

  • Cylinder Expansion
  • Piston Slap
  • Scratches On The Cylinder Walls
  • High Oil Consumption
  • Too Much Blowby Gas
  • Carbon Buildup
  • Clogged Fuel Injectors

We are familiar with the common problems with the Kia 2.5 turbo, now let’s further elaborate on these issues in detail and learn when and how they appear. We are going to cover the symptoms and also how serious these issues really are. So, dive in.

Cylinder Expansion

The biggest problem with this engine starts in the combustion chambers. This engine is using something known as direct injection.

Direct injection is a modern fuel injection system that not a lot of carmakers are able to master quite yet, including Hyundai. Even after all these years, their engines suffer from the same problems. Including the 2.5 engine.

What happens is that the direct injection system creates a lot of heat inside the cylinders. This heat is so high that it basically heats up the cylinder walls and they start to expand.

This situation will cause many issues since the tolerances between the piston and the cylinder wall will increase.

And most of these problems that we are going to cover in the following chapters build up from here.

What is interesting is that some Korean engines were affected by this problem but the issue is not that present in the US.

Piston Slap

Since the cylinder walls are expanding because of the immense heat that is created from the direct injection system, there will be a situation known as a piston slap. So, what is a piston slap?

A piston slap is a situation where the side of the piston is quite literally slapping against the cylinder walls. As you know, pistons should move almost perfectly and not have play.

So, what happens in this case, is that the pistons are clearly having too much room between them and the cylinder walls.

So, consequently, they start to bang the cylinder walls. In this case, you will hear a tapping sound coming from the engine, especially at a cold start.

So, if you notice this noise from the engine, this means that you probably experience a piston slap.

Scratches On The Cylinder Walls

Another consequential problem of the piston slap is the situation when scratches start to appear on the cylinder bore.

Cylinder bores are machined to perfection, they have factory grooves in order to make the piston rings seal the best they can.

And whenever you have a piston that is out of balance and is slapping the cylinder wall or bore as people call it, you will have engine damage.

There will be scratches on the cylinder wall and some of the material will be lost in the process. Permanently damaging the engine in the process.

In many cases, the only solution to this problem is to simply replace the whole engine and call it a day.

High Oil Consumption

High oil consumption is another common symptom caused by this problem with the expanded cylinder bore.

This is the case because the bore is wider after many heat cycles and the pistons do not seal well. The compression rings are not doing their job. And also the oil control ring is not regulating the engine oil.

So, what you have is oil that goes by the rings and ends up in the combustion chamber. Oil consumption on these engines is pretty much astronomical.

This is why you need to take this problem into consideration. The core problem with this engine is creating so many different problems that basically destroy the engine’s life.

What is worth noting is that this oil consumption can be up to a quart every 1,000 miles or so. These numbers are completely bad and if you don’t top off the oil regularly, the engine will simply fail from oil starvation.

Too Much Blowby Gas

Another problem that will develop as a consequence of this problem with the bigger clearance in the cylinders is the increase of blowby gas from the crankcase.

As you probably know, inside the crankcase there is a lot of evaporation that occurs and these gasses are called blowby.

There is a special system that is known as the PCV system to clear the blowby pressure. But in this case with the Kia 2.5 engine, this pressure will pass between the pistons and the cylinders and will end up on the intake ports of the engine.

On some of the most seriously damaged engines, the intake ports are soaked with engine oil. And on some higher mileage engines, they are soaked both with carbon deposits and oil which create a big sludgy mess on the valve stems.

Carbon Buildup

Carbon buildup is also a common thing on these Kia 2.5 turbo engines. This is the case since oil will enter the combustion chamber.

These engines have a few fractions of an inch of carbon deposits on the piston crown. If you don’t know, the crown is the flat top of the piston.

In addition to the crown, there is also a lot of carbon buildup on the piston rings. This carbon destroys the piston rings.

It will simply glue the piston rings to their mounting point, which is something that shouldn’t happen.

Also, there will be carbon on the engine valves from the combustion chamber side.

Clogged Fuel Injectors

Another consequence of the cylinder expansion of this 2.5 turbo engine is the situation with the injectors.

Fuel injectors tend to clog up because, on the tip of the injector, there will be a lot of carbon deposits. Read our article on fuel injector problems to learn more about this phenomena.

These carbon deposits will first ruin the spray pattern of the injectors and then they will completely clog the injectors.

The only way around this problem will be to manually clean the injectors from carbon buildup on the tip. If they are not completely ruined from this type of work for thousands of miles.

Which Models Have The Kia 2.5 Turbo Engine?

Smartstream G2.5T (G4KP)

  • Hyundai Sonata 2020 – Present
  • Hyundai Santa Fe 2020 – Present
  • Hyundai Santa Cruz 2021 – Present
  • Kia K5 2020 – Present
  • Kia Sorento 2020 – Present

Smartstream FR G2.5T (G4KR)

  • Kia Stinger 2020 – 2023
  • Genesis G70 2020 – Present
  • Genesis G80 2020 – Present
  • Genesis GV70 2020 – Present
  • Genesis GV80 2020 – Present


What Are The Common Kia 2.5 T-GDI Problems?

The biggest problems with this engine are the carbon deposits, oil consumption, piston slap, cylinder scarring, and clogged injectors. Overall, pretty destructive problems. But what is worth noting is that these problems do not affect each 2.5T engine.

Is The 2.5 Kia T-GDI Engine Reliable?

It really depends, there are positive stories, and there are also some horror stories. These engines develop issues such as carbon deposits and piston slap, that’s a fact. But on what extent, it really depends on the maintenance of the engine, as well as on luck. If you buy it new, it should be reliable for at least 100,000 miles. 

If you want to boost the reliability, it is recommended that you do an oil change every 5,000 miles, this way the engine will always have fresh oil and will be less prone to developing these problems.

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