The rubber vibration damper on the crankshaft pulley comes loose on many BMW 1 Series models. This concerns the version with a 1.5-litre, three-cylinder engine. As a result, the alternator and water pump stop working. The charging warning light then comes on and the engine is at immediate risk of overheating. Find out exactly what happens and how to spot this in good time.
What goes wrong with the vibration damper
The crankshaft vibration damper is also known as a harmonic balancer. It is a pulley with a rubber layer that absorbs vibrations. The vibration damper is mounted at the front of the engine. It absorbs vibrations from the crankshaft. This pulley drives the alternator and water pump via a belt. The part consists of a steel disc with a rubber intermediate layer that absorbs the vibrations. On the 1.5-litre three-cylinder engine in the BMW 1 Series, this rubber layer regularly fails.
The rubber comes loose. After that, the outer ring no longer turns in sync with the crankshaft. The belt slips or stops altogether. As a result, the alternator no longer supplies power and the water pump no longer circulates coolant. This often happens without a clear prior warning. Many owners only notice while driving that the charging warning light on the dashboard of the BMW 1 Series comes on.
‘ So stop immediately when this warning light comes on. ’
What does the charging warning light mean on the BMW 1 Series 118i
The charging warning light in the shape of a battery indicates that the alternator is no longer supplying a charge. Without a working alternator your car runs on battery power. This battery power runs out quickly. At the same time, the water pump stops circulating coolant. As a result, the engine temperature rises rapidly.
If you keep driving, the engine will overheat within a few minutes. This can lead to leakage of the head gasket. A head gasket is the seal between the cylinder head and the engine block. The cylinder head can also warp or in the worst case the engine can suffer total failure. So stop immediately when this warning light comes on. Switch the car off and let it cool down before you drive on or call for help.
Why does the vibration damper fail on this model
The 1.5-litre engine has three cylinders. A three-cylinder is an engine with three combustion chambers. It produces more vibrations than a four-cylinder with four combustion chambers. This is due to the uneven firing order. That puts extra stress on the rubber layer in the vibration damper. Over time, the rubber deteriorates due to:
- Heat from the engine that makes the rubber brittle
- Constant vibrations that cause small cracks
- Changing loads during acceleration and deceleration
- Age and mileage, especially above 100,000 kilometres
The BMW F40 1 Series has the B38 engine. This is a three-cylinder petrol engine with a 1.5-litre capacity. This problem occurs more often on this model. Other BMW models suffer from it less frequently. Owners of the 118i regularly report this defect online. The 116i and 120i with the same engine design can also be affected.
Symptoms before the damper completely fails
The vibration damper sometimes gives signals before it fails completely. Watch out for the following warnings:
- A knocking or ticking noise at the front of the engine, especially at low revs
- Vibrations in the steering wheel or bodywork during acceleration
- A metallic noise when turning the steering wheel while the engine is idling
- Visible cracks in the rubber of the pulley when inspecting under the bonnet
If you hear or feel these signals, have the vibration damper checked as soon as possible. Replacing it as a precaution helps prevent you from breaking down at the roadside.
‘ Note: don’t use excessive force to avoid damaging the crankshaft. ’
How to replace the crankshaft pulley vibration damper
Replacing the vibration damper requires basic knowledge of engine maintenance. You also need the right tools. Follow these steps:
Gaining access to the pulley
Turn the right-hand front wheel fully to the left. This gives you more room to reach the pulley. The crankshaft pulley is the pulley at the end of the crankshaft. If necessary, remove the front wheel completely for optimum access. Remove the lower engine cover if it blocks access to the pulley.
Removing the old damper
Use a ring spanner to secure the crankshaft bolts at the back. These bolts are located on the flywheel at the rear of the crankshaft. This prevents the crankshaft from turning. Undo the central bolt on the pulley. You will usually need an Allen key or hex socket for this. Pulleys are the discs that drive other components via belts. On pulleys that are stuck, a gentle tap with a soft hammer can help. Then carefully tap the pulley loose. Note: don’t use excessive force to avoid damaging the crankshaft.
Installing the new damper
Clean the crankshaft mounting face before fitting the new damper. Lightly lubricate the thread of the central bolt. Fit the new pulley and tighten the bolt by hand first. Use a torque wrench to tighten the bolt to the manufacturer’s specification. This is the tightening torque specified by the manufacturer. Check that the thread protrudes through any locking nut for correct locking.
Refit all parts in the reverse order. After assembly, test the engine at idle. Then listen for any unusual noises. Drive a short test run carefully and check again.
Costs and choice of parts
An original BMW vibration damper costs between 150 and 250 euros. This price difference depends on the supplier and type. Aftermarket versions are often cheaper, from around 80 euros. Pay attention to quality when choosing. Cheap rubber wears out more quickly. In the end this will cost you more money and hassle.
The labour time for replacement is between one and two hours. The exact time depends on how easy it is to access the pulley. The mechanic’s experience also plays a role. At a garage you should expect total costs of between 250 and 400 euros including parts and labour. If you do the job yourself, you only pay for the parts.
Is this problem widespread on the F40 BMW 1 Series
The defect of the vibration damper occurs more frequently on the F40-generation BMW 1 Series. It specifically concerns the three-cylinder version. This is the engine with three combustion chambers. Other BMW models suffer from this problem less often. On forums and in owner groups, several drivers report this issue, especially on cars older than five years or with more than 80,000 kilometres on the clock.
BMW has not issued an official recall for this part. A recall is a factory campaign in which a defect is rectified free of charge. This means that replacement is at your own expense, unless your car is still under warranty. Preventive maintenance is therefore sensible, especially if your car is approaching 100,000 kilometres.
‘ A small investment now can save you from expensive engine damage later. ’
Prevent major damage with timely checks
Check the vibration damper at every major service. Also pay attention to it when having the belt changed. This refers to replacement of the auxiliary drive belt. A quick visual inspection often already reveals cracks or separation of the rubber. In doubt whether the damper is still firmly attached? A mechanic can feel during a test drive whether the damper is coming loose. He then holds his hand under the car near the pulley while accelerating.
Replace the damper as a precaution at mileages above 100,000 kilometres. This is especially sensible if you often drive in a sporty manner. Heavy loading of the car also calls for preventive replacement. A small investment now can save you from expensive engine damage later. Also keep an eye on the charging warning light. Does it come on while driving? Then stop immediately and switch the engine off.
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Frequently asked questions
The vibration damper on the crankshaft of a BMW 1 Series absorbs the harmonic vibrations caused by the uneven combustion in the engine. This allows the engine to run more smoothly and protects components such as bearings, drive belts, alternator and water pump from excessive loads. This is important to prevent premature wear and possible engine damage. In the event of a defect or wear, ticking or knocking noises can occur and ultimately serious damage can result.
Symptoms of a defective vibration damper on a BMW 1 Series are mainly knocking or ticking noises at the front of the engine, especially at low revs or during acceleration. You may also experience belt slip or a grinding metal-on-metal noise if the rubber part is worn and the pulley comes loose. Sometimes you notice rough running and vibrations because the harmonic vibrations in the crankshaft are no longer damped properly. In severe cases there may be noticeable play or damage to the pulley and belt.
A defective vibration damper can cause the crankshaft to vibrate excessively, which leads to extra wear or even damage to bearings, belts and adjacent engine parts. The rubber part can tear further, causing the pulley to come loose, with a risk of belt slip or breakage and failure of accessories such as the alternator and water pump. Driving on for a long time can result in metal-on-metal contact and serious engine damage. In addition, vibrations and knocking noises can increase, reducing the driving comfort and reliability of the BMW 1 Series.
Replacing the crankshaft vibration damper on a BMW 1 Series usually costs a few hundred euros, depending on whether you choose an OEM or aftermarket part and on the garage’s labour costs. The part itself is relatively inexpensive; most of the cost is labour. With the right tools and some mechanical experience, it is in principle a job you can do yourself. If you have little experience with engine mechanics, it is wiser to have a professional do the work.
Yes, there are aftermarket vibration dampers available for the BMW 1 Series. These are often made from robust steel and high-quality rubber and are designed for high-performance use, for example on N55 engines. They can improve durability by absorbing harmonic vibrations more effectively and thereby reducing wear on bearings, belts and accessories. At higher mileages or on tuned engines, such aftermarket dampers are regularly used as an upgrade or preventive replacement.