A lot of Mini cars are equipped with the 3-cylinder 1.5-liter diesel engine codenamed B37C15A. This is actually the B37 BMW engine that is used by Mini under a separate name. I will discuss it today within Mini vehicles just because it’s pretty widespread in Europe exactly in these cars.
So, the 1.5L diesel engine was introduced in 2014. It has been used in the Clubman, Countryman, 3D and 5D Hatch, and also in the Cabrio. While the Hatch and the Cabrio aren’t using this engine right now, the Clubman and Countryman (up to the 2023 model year) still come with the B37 machine under their hoods.
I will tell you more about the specs, peculiarities, and also common issues with these engines to let you drive it longer and avoid the problems.
What should you know about the 1.5L diesel engine in Mini cars?
First of all, this is exactly the BMW engine with no changes or modifications. As already said, this is the 3-cylinder engine and the little brother of the B47C20A which I’ve already described in another article. The only difference is the displacement due to an extra cylinder in the latter.
There are two modifications available – they basically differ in power and torque. The more powerful version is also known to be a little less durable. But overall, the engine is very decent in terms of its durability and reliability.
Here’s what you may want to know about it:
- the engine is a 3-cylinder 1.5-liter diesel engine with a Mahle turbocharger producing 95 or 116 horsepower;
- its torque is what you will love it for – the engine provides you with 220 or 270 Nm of torque, depending on the version;
- the injection system is Common Rail – probably the best and most reliable diesel injection out there;
- the camshafts are driven by the chain, there are no phasers on them, also, the engine is equipped with hydraulic lifters;
- the engine comes with a 6-speed manual transmission or with the 7-speed DCT, conventional automatic options were available for just some years;
- the fuel consumption is advertised at 4.3 L/100 km in the city and 3.5 L/100 km on highways for the Hatch (66-80 MPG UK).
The fuel economy is probably one of the most significant advantages of the engine. It’s perfect for both city driving and long journeys on highways. I wouldn’t say the power is super-high and sometimes you feel this. However, the high torque compensates for the lack of power and makes driving fun.
There are concerns about the DCT transmission (the one with 7 speeds). Although this is not the worst dual-clutch gearbox in the world, it still comes with a pack of problems and you will need to pay attention to the clutch pack and control module from time to time. Unfortunately, this is quite expensive.
How many kilometers will the 1.5L diesel go in your Mini?
So, the 1.5 diesel engine will go approximately 240,000-270,000 kilometers (150,000 – 170,000 miles). It’s a lot for a 3-cylinder engine. And this is maybe one of the most durable Mini engines that I can think of right now.
Such durability is possible thanks to pretty simple construction and no experiments in engineering. For instance, the engine has a perfect fuel injection system and requires minimal maintenance by adjusting the valves with hydraulic lifters.
All you need is to change the oil and filters and also pay attention to the loads. This is a weak and small engine, so if you try driving it as if it were a sports vehicle, you are going to get about half of its potential longevity, in the end.
Also, the quality of fuel is super-important. Any contaminated or just poor-quality diesel fuel will result in injection problems, in the long run.
What are the common problems with the 1.5 diesel engine in Mini?
Well, although this is one of my favorite BMW engines, I still doubt it comes without several surprises. Every engine has certain flaws and this one is no exception. I should say that the majority of problems will show up after the engine crosses the 150,000-kilometer mark and they will get worse when it approaches its average lifespan milestone.
Here’s what you may want to pay attention to in the B37C15A engine:
1) The EGR system
As in all diesel engines, there is an EGR (somehow called AGR) in the 1.5L diesel engine in Mini vehicles. This system works well for about 150,000 km (90,000 miles) and then starts freeing out.
The valve may be clogged, the EGR gases may damage the throttle, etc. Sometimes, proper cleaning may solve the problem, but if there is an issue with cooling the EGR valve or the problem is old and mistreated, the valve itself will need replacement.
2) Timing chain premature failure
Although timing chains are not bad here, they are still not enough for the entire lifespan. Fortunately, the chain will start rattling significantly before it fails. If you ignore the rattling sound, the chain will quickly break and cause irreversible engine damage.
To avoid this, replace the chain kit at about 180-200 thousand kilometers (110,000-120,000 miles). The chain kit is not extremely expensive and the labor is not very complicated.
3) DPF may get clogged
As with all diesel engines, this one is fitted with the DPF or Diesel Particulate Filter. It gets clogged at about 200,000 kilometers (120,000 miles) and requires replacement. You will feel significant power loss, there will be codes in the ECU showing the poor work of the DPF.
Sometimes, DPF cleaners may help if the problem is not that bad. But, in most cases, if this happens at high mileage, the DPF will need to be replaced. It’s quite expensive.
4) Intake problems
The turbocharger is overall very reliable but it has the so-called variable geometry. This is the system that allows the turbo to adjust airflow in accordance with engine load and RPMs. This system and the intake manifold may get dirty and stop functioning.
One of the possible solutions is to change air filters more often. But this is kind of a common problem, so the turbocharger and the intake manifold will require some attention from time to time.
5) Vibrations and sudden loss of power
Vibrations are very common for early models of the B37 engine. After 2017, BMW upgraded the machine and it stopped causing this kind of problem. If you have an older engine, you will need to just put up with some vibrations when idling. This is a feature, not a problem.
Sudden loss of power may be connected with the injector problems. The Common Rail is very good in these engines but it may fail because of dirty or low-quality fuel. Also, the loss of power may come from DPF or EGR problems.
How can you prolong the lifespan of this engine?
The 1.5L diesel engine in your Mini may live a very long and happy life if you maintain it and don’t ignore problems. If you experience any issues (weird sounds, excessive vibrations, loss of power), immediately go to a good repair shop or dealership and have the engine diagnosed.
Here are some tips to help you drive the Mini engine longer than average:
- don’t experiment with the oil types and brands, also change the oil more often than the manufacturer recommends;
- check the EGR at about 150,000 km – it may require some service to prolong its life;
- replace the chain kit at about 200,000 km to let the engine run some more kilometers for you;
- avoid aggressive driving – this is certainly not the sports-ready machine;
- get a good scanner to properly diagnose your Mini once something is wrong with the engine;
- be careful with the 7DCT transmission – it may require a lot of attention at high mileage.
Other than that, you will just need to remember some common-sense requirements to happily drive your Mini for a lot of years with almost zero problems.
Do you have experience with these Mini engines? Please share it in the comments below to let other drivers know!
