As the BMW S55 engine gets older, we are learning more and more about long-term reliability, common problems, and important preventative maintenance.
It's no secret that aging high-performance BMWs need more maintenance than your average vehicle. Many older BMWs, especially M cars, have acquired quite a poor reputation for dependability - particularly when the miles start to stack up. But we don't think it's always deserved.
Sure, there are a few examples such as the rod bearings found in the BMW E60 M5's S68 V10 that would wear prematurely, fail, and cause catastrophic engine failure. There was also the VANOS issue that affected the BMW E46 M3. The tabs on the camshaft hubs would break off, end up in the timing chain, and cause catastrophic engine failure. It's a similar story for the V8-powered E9X BMW M3 which commonly suffered from rod bearing failure, throttle body actuator failure, oil consumption, and more.
Lots of these reliability issues aren't unique to BMWs but, for certain models, the failure rate was unnaturally high.
BMW S55 Engine
That brings us to the S55 engine from BMW. This engine was the first M3 engine to feature turbocharging - quite controversial at the time. The S55 powerplant offered relentless low-end torque, great power and decent efficiency.
Which BMW models have the S55 engine?
The S55 engine can be found in the BMW F80 M3 (2014-2019), F82/F83 M4 (2014-2020) and also in the F87 M2 Competition (2018-2020). The non-Competition version of the BMW F87 M2 did NOT feature the S55 engine - this version was given the N55 powerplant found in the BMW M235i at the time.
Is the BMW S55 engine reliable?
Just like most engines on the market, when serviced & maintained regularly, the S55 engine can be very reliable. However, due to the highly-strung nature of the engine, more frequent/thorough maintenance is required to keep the S55 healthy.
With S55-powered BMWs now getting on in age, there are many examples on the market with high mileage, patchy service records, and a very tempting asking price. On the low end, you can now pick up an F82 M4 for around £20,000 in the UK. These examples tend to have over 100,000 miles on the clock and a shopping list of owners, but still quite attractive at the price point.
Due to the nature of these vehicles, many examples have had very hard lives and, as they become cheaper, they will likely suffer the same issue that affected the E46 M3, for example. They are bought by people at £20,000 who aren't prepared to pay the servicing costs of a £60,000+ car, leading to deferred maintenance and an increased risk of going bang.
BMW S55 engine common problems
1. Crank Hub
We'll get straight into it and address the elephant in the room: the Crank Hub. Crank hub failure occurs when the hub's friction unit plate slips/spins causing the timing of the engine to alter which can cause piston-to-valve contact. In short, the engine is toast. If the vehicle isn't completely unmodified and within warranty, this leaves owners with a very expensive repair bill.
If you've been on the forums, you will have heard horror stories from many owners, however, this issue has only affected an estimated 2-3% of vehicles thus far. It's also important to note that tuned/modified vehicles are disproportionately affected.
BMW S55 engine crank hub fix
If you are concerned about your BMW S55 engine spinning its crank hub, there are a number of solutions available. The most affordable option is a crank hub capture plate. The capture plate secures the head of the OE crank bolt and prevents it from turning or being able to loosen. There is no need to remove the engine to install this upgrade - simply drop the radiator in order to gain adequate access to install.
The alternate and more expensive option is a complete replacement upgraded crank hub such as an MMR full crank hub kit. This crank hub kit ensures the friction plates can't slip and with a new crank bolt tightened appropriately, this delivers a substantial improvement in reliability versus the OE version. It offers the most comprehensive solution on the market at one of the most compelling price points.
BMW S55 engine crank hub failure symptoms
- Engine fault codes
- Drivetrain malfunction light
- Rough idle/stuttering
- Knocking or rattling noise
There are no early signs of crank hub failure. Failure will be sudden and catastrophic.
How much does the BMW S55 crank hub fix cost?
The process is very labour intensive and, depending on which upgrade you choose, prices can range from around £1,000 to £2,500 on the higher end.
2. Charge Cooler
Charge cooler failure is another common problem. We had this issue with our BMW F80 M3 development car. Due to BMW using cheap, plastic materials, it's not uncommon for these components to split as they age. When we opened up the engine, we found water had gone through the car's intake system and bent a conrod. The car had done around 85,000 miles and needed a full replacement engine.
An upgraded charge cooler is not too expensive and is a great step in preventative maintenance. Ensure the upgrade uses higher-quality materials such as the VRSF top mount charge cooler. Whilst you're there, why not also upgrade your vehicle's charge pipes? We run the Eventuri carbon fibre charge pipes on our F80 M3 and were really impressed with the quality and fitment.
3. Valve Cover Gasket
As with many modern BMW engines, the S55's valve cover gasket is prone to cracking and leaking oil. As the vehicle ages, the gasket rubber hardens and with endless heat cycles, the gasket eventually cracks - allowing oil to leak out.
This is a very common issue for the S55. It's not uncommon for the valve cover to begin leaking before 60,000 miles.
BMW S55 engine valve cover gasket leak symptoms
- Low engine oil light
- Burning oil smells
- Smoke coming from valve cover area
- Oil on spark plug threads
Fortunately, this only becomes a serious issue when oil starvation occurs. If you ensure your oil level remains optimum and fix the issue as soon as possible with a replacement valve cover gasket, you'll come away with not too much of a bill. We recommend also replacing the valve cover as well whilst you're there as this too can fail over time - although far less common.
4. Oil Pan Gasket
Just like the BMW S55 valve cover gasket, the oil pan gasket is also prone to cracking and leaking over time. Replacing this failed gasket require dropping the sub-frame which is a very labour-intensive process. A replacement S55 oil pan gasket is very affordable as well as the required S55 oil pan gasket screws.
BMW S55 engine oil pan gasket leak symptoms
- Low oil level
- Oil left on the ground beneath your vehicle when parked
If at any point your vehicle's subframe needs to be dropped for suspension work etc. we recommend changing the oil pan gasket as a bit of preventative maintenance.
BMW S55 engine servicing
BMW recommends you change your S55 engine's oil and filter every 10,000 miles or 12 months - whichever comes first. As your vehicle ages, we think it's worth servicing and inspecting your S55-powered BMW every 5,000 miles or 6 months. Some might think this is excessive but with an ageing vehicle, regular inspections will likely flag up any potential issues before they have time to get worse. If you're driving hard, this is even more important.
We cannot stress the importance of doing all preventative maintenance before you begin modifying and tuning your vehicle.
For DCT gearbox oil, we recommend changing this every 50,000 miles or 5 years. Most BMW main dealers will not touch this as the manufacturer claims many of their automatic gearboxes are "sealed for life". You will have to find a BMW specialist to carry out this service item. As a result, very few examples seem to have had a DCT gearbox service carried out.
Is the BMW S55 engine reliable? In short, the S55 engine can be very reliable when maintained correctly and with all preventative maintenance carried out ahead of time. Mechanical sympathy is also advised i.e. do not drive enthusiastically until vehicle is up to operating temperature.
Don't be put off by YouTube comments or people in Facebook groups talking about how they "wouldn't touch an S55 BMW with a bargepole". They truly are amazing cars and if you maintain them correctly will offer immense driving pleasure for many miles to come!