7 BMW B48/B46 Engine Problems (inline 4-cylinder 1.6/2.0L)

Are you looking for a BMW model with the B48 or B46 engine and you want to learn more about the common BMW B48 engine problems? Well, if that is the case, you will find this article quite useful!

Researching before you decide to purchase a car with a specific engine should be one of your top priorities. Mainly because each engine is susceptible to different problems that in some cases can be very serious. And this is why we are here to help you out.

First, we are going to learn the basic B48 engine specs, common BMW B48 engine problems, and the applications of this engine. Lastly, we are going to cover some frequently asked questions. So, if you want to learn more, follow along!

P.S.: The B46 and the B48 engines are essentially the same, which is why we have combined them in a single article!

Basic BMW B48 Engine Specs

First let’s cover the basic specs of this B48 engine and learn more about the numbers it delivers. The engine was introduced in 2014 and is still produced today. This is an inline-4 engine that implements a single twin-scroll turbocharger and direct injection.

What is interesting to note is that this model replaced the N20 engine that we previously covered.

When it comes to the engine, there are two main types. The base is the B48B16. This is the 1.6L inline-4 engine.

  • B48B16 1.6L version
    There is only one variation of this engine that is pushing 168hp and 250 N-m (184lb-ft) of torque.

    Then there is the B48B20, this is a 2.0L inline-4 engine that is a base for many variations. There are a total of 11 variations of the B48B20 engine.
  • B48B20 2.0L version
    The least powerful model is pushing 154hp and 250 N-m (184lb-ft) and the most powerful model is pushing 225 kW (302hp) and 450 N-m (332lb-ft) of torque.

    The ability to produce such a wide range of variations is because this engine is boosted. It uses turbocharging and by doing so BMW can tweak this engine in the way they like to get the power they need for a specific application.

Common BMW B48 Engine Problems

Now let’s list the common BMW B48 engine problems and learn what are the issues that trouble this engine.

Common BMW B46/48 engine problems include:

  • Counter Balance Shaft Bearing Failure
  • Valve Cover Gasket Leaks
  • Cooling Problems
  • Turbo Return Line Oil Leak
  • Water Pump Failure
  • Carbon Buildup
  • High-Pressure Fuel Pump Failure

What is worth noting is that these issues are also associated with the B46 engine. Now that we briefly listed the common problems with this engine, let’s now move on and further elaborate on these issues and learn more about the problems.

B48 Counter Balance Shaft Bearing Failure

The counterbalance shaft bearing failure is something serious when it comes to the B48 engine. This is something still quite new but in Germany, there was a recall issued on this specific issue.

In the engine, there is a counterbalance shaft to balance the engine and this shaft has a bearing. 

These bearings can fail and cause premature engine failure. For more information on the problem, you can check the link that we attached from a BMW forum.

Nevertheless, the models of engines that were recalled were the B48D, B48C, and B46D. Both RWD and AWD models. As we could note from the document, the models affected have the G-letter in the code name. Namely G20 models, which is actually the 3 Series.

This engine problem also affects some Mini models as well. A lot of Mini owners reported excessive play in the crankshaft of the engine. So, before buying a BMW with this engine, you should make sure that the model was affected by these recalls or not.

Valve Cover Gasket Leaks

A BMW would not be a BMW if it does not have valve cover gasket leaks. Almost every engine they make is somewhat affected by this problem.

There are either cracks on the valve cover or the gasket is leaking. Both of these situations can lead to grease spots appearing on the side of the engine and loss of engine oil.

If you notice something like this on your B48 engine it is really important to react quickly because this could lead to excessive oil loss. 

You definitely don’t want to leave your engine running low on oil and trust me, even though these leaks might seem small, they are actually causing your engine to lose a significant amount of oil.

Cooling Problems

Cooling problems with this B48 engine are also very common. Namely, there is a problem with the coolant hose that is located under the intake.

This coolant hose is susceptible to many failures. There were more than a handful of reports that we found on the issue.

So, you need to be aware of these leaks if you want to prevent the engine from overheating and possibly replace this coolant line as preventive maintenance if the engine is above 100,000 miles (ca. 160,934 km). This way, you will be somewhat sure that the problem will not appear.

Not to mention that these problems can be fixed on the cheap. Only a new coolant hose and a coolant flush are needed.

Water Pump Failure

Another fairly common problem with the B48 engine is the water pump failure. Water pumps are notorious for failing on these engines.

Many of these water pumps fail at 110,000 miles (ca. 177,028 km). There were a couple of reports that we found on this specific issue and many of the owners reported failure somewhere at this mileage.

This is why we recommend replacing this pump every 80,000 miles (ca. 128,748 km) or so, just to avoid these issues. What is good about this pump is that it is mounted externally, not internally. This means that it is cheaper to replace the pump since the timing chain does not have to come off like in some other applications.

Turbo Feed/Return Line Oil Leak

Many owners also reported oil leaks in the turbo lines. As you probably know, the turbocharger of the engine has to be properly lubricated.

This means that the engine needs to get oil, if not it will fail. There are specific lines that go into the turbocharger and out of the turbocharger.

These oil lines are notorious for causing leaks. These leaks are hard to spot but you will definitely start to lose some oil. In addition to this, there will be a burning smell because the turbo is often quite hot and creates a ton of heat.

Luckily, replacing these lines is not very difficult and could be done for a good price.

Carbon Buildup

The next problem on our list of BMW B48 engine problems is the carbon buildup. As we noted previously, the B48 engine is a direct injection engine. So, what does this mean?

Well, this means that the engine is susceptible to carbon buildup problems. In old-school engines where fuel is injected through the intake ports, the intake valves are washed by the gas.

In direct-injection engines, the fuel is not injected this way. In this design, there is a high-pressure fuel injector located on top of the cylinder.

By doing so, the engine valves are not cleaned and there are a lot of carbon deposits that stick to them. This can become a problem and the valves will stop opening and closing correctly if you don’t walnut blast them every 60,000 miles (ca. 96,561 km) or so. This process is a must on many of these direct injection engines.

High-Pressure Fuel Pump Failure

High-pressure fuel pumps are another integral part of the direct injection system. These pumps also tend to fail a lot in BMW engines.

Luckily they often appear on older engines. So, the first few years of this engine are more prone to HPFP failure than newer ones.

This is why it is often recommended that you opt for a newer model instead of the older versions of this engine.

Which Models Have The B48 Engine?

Now let’s briefly take a look at which applications this engine appeared in. There are a total of 11 variations, so in order to save some time, we will only add the models.

  • BMW 1 Series, F20, F40,
  • BMW 2 Series, F22.F23, F44, G42, UO6
  • BMW 3/4 Series, F30/F31/F31/F33/F36, G20/G21,G22
  • BMW 5 Series G30/G31
  • BMW 7 Series G11
  • BMW X1 F48
  • BMW X2 F39
  • BMW X3 G01
  • BMW X4 G02
  • BMW Z4 G29
  • Mini Cooper F54/F56/F60
  • Toyota Supra J29/DB22, J29/DB82


Overall, the B48 is a big improvement compared to its predecessor, the N20. This engine is a very reliable engine. Possibly the first inline-4 that BMW built the right way.

This is why we would recommend this engine to you. The crankshaft counterbalance shaft bearing is probably the problem that you need to be aware of. Since this problem can total the engine. Besides that everything is good with this engine.


What Are The Common B48 Engine Problems

Problems with the B48 engine include problems with the crankshaft counterbalance shaft bearing, in addition to this, there are also coolant leaks from the coolant hose under the intake, water pump failures, turbo oil lines can leak, carbon buildup and HPFP failures are also common.

Is The B48 Engine Reliable

The B48 is a very reliable engine. Except for the counterbalance shaft bearing failure that appears on some of these engines. So, make sure that the engine that you plan to buy is not one of these models that have reliability issues.

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