The 5 Most Common BMW S65 Engine Problems

The BMW S65 engine is a racing-derived engine built specifically for high performance, with few accommodations for improved reliability. Along with the high-performance goal for the S65, the V8 also has engine technology that reflects that. Unfortunately, those aspects of the engine are what are most likely to fail in some instances.

For example, the S65 features individual throttle bodies for improved throttle response, but the actuators are prone to failure. Rod bearing failure can also be (somewhat) attributed to the S65’s high-strung nature due to the tight tolerances required for such a high-revving performance engine.

Outside of those issues, the other common S65 problems that we’ll cover in this article are pretty typical of most BMW engines, especially BMW engines that are over 15 years old at this point. Valve cover gasket leaks and PCV issues are known issues that are not exclusive to the S65, but are still an annoyance regardless. We’ll go into all of these issues in detail in the sections to come.

1. Rod Bearings
2. Throttle Body Actuators
3. Idle Control Valve
4. Valve Cover and Gasket
5. PCV Issues

S65 Rod Bearing Failure

This will no doubt be the first thing that comes up when you google the S65. The deadly rod bearing failure.  The rod bearings in the S65 have a tendency to wear out prematurely, which could end in engine failure. This seems to be the number one issue that numerous forums call out.

The only solid objective information you can count on is that less than <1% engines have failed from rod bearing failure and that it has not correlated with miles or even tracking. Everything else is subjective interpretations and inconclusive. – Rajmun340

Due to the fact that the S65 is a high-performance engine that was specifically engineered to be a high-revving and highly-strung engine, its tolerances are extremely tight. That is especially true of the rod bearing to cam journal clearances at only .001-inch. The tight clearance makes it hard for oil to saturate the bearing, especially if the oil isn’t up to temperature or if the wrong oil was used in the engine.

If oil doesn’t create a lubricating film between the rod bearings and cam journals, the metal of both surfaces make direct contact, leading to damage. Since the rod bearings are made of soft metals like copper and lead, they are more likely to get damaged which can spell serious disaster, or the complete destruction, of the engine. Unfortunately, rod bearing failure usually occurs without any warning, making it a serious issue if you don’t know that it is a common problem on the S65.

While there aren’t usually any noticeable symptoms of rod bearing wear, it is possible to have your oil analyzed to check for rod bearing debris which can give you an indication of rod bearing health. There is no set window that S65 rod bearings typically fail, however, most enthusiasts recommend replacing them every 50-80k miles.

If you want to read more about BMW rod bearing failure in more detail, we wrote an entire article about it which you can read here.

Rod Bearing Failure Symptoms

• Rod knock
• High concentration of lead or copper in engine oil
• Engine completely seized and not turning over

Replacement Part: https://www.bimmerworld.com/Engine/Engine-Maintenance/S65-Treated-Rod-Bearing-Upgrade-Kit_2.html

Replacement Cost: approx. $2,500 for parts and labor. We recommend replacing these every 60k miles. The alternative is a $25k repair bill for a completely new engine!

There are a number of aftermarket S65 rod bearing options available if OEM bearings aren’t available to you or if you are looking for a less expensive option. Some aftermarket bearings were designed with S65 rod bearing issues in mind and are made of harder metals than the OEM bearings. Depending on how you look at it, that can be a good or a bad thing. While they have better structural rigidity than the OEM bearings, they can’t be as easily checked for wear with an oil analysis.

Here is a clip of the noise:

Throttle Body Actuator Failure in S65 Engines

Throttle body actuator problems are, no doubt, the second most notable common problem on the S65 V8. As with most other BMW M engines that came before it and after it, the S65 uses individual throttle bodies on each cylinder to increase power and throttle response. However, the throttle bodies don’t get their own actuator. There are two central actuators that control the throttle bodies on each cylinder bank that control 4 TBs each.

These are prone to fail in this V8, and the mileage reported for the failures varies. The failure is actually caused by the plastic gears inside of the actuators wearing out and breaking over time. In addition to the plastic gears wear down, there is also an electrical component to ITB actuator failure too. Over time, and with constant and repeated strain, the circuit boards within the actuators burn out.

When the throttle body actuators fail, it will cause the engine to go into limp mode, lose engine power, and the DSC and EML lights will illuminate. Actuator failure isn’t a critical failure that will do damage to the engine, but it will make driving the car a lot less enjoyable.

While there are a number of quality actuator rebuild kits on the market, it isn’t worth rebuilding the units this far past the engine’s build date. At this point, it makes way more sense to just replace the unit/units altogether for peace of mind more than anything.

S65 Throttle Actuator Failure Engine Codes:

• Fault Code: CDC0 – Throttle Value Actuator CAN Message
• Fault Code: 2B57 – Check At Lower Top
• Fault Code: 2B21 – Predriver Check Throttle Valve Actuator

Replacement Part: OEM S65 Throttle Body Actuator

Replacement Costs: $722.99 for parts, $1,000 for labor

Then factor in labor which has been quoted on a few forums for nearly $1000. In addition to the $722.99 part cost for a single actuator, it is a very expensive job if you opt to take it to a dealer. Some BMW specialty shops will likely be able to do the job for a bit less, but they will charge quite a few hours regardless.

If you are relatively handy, and think you can DIY it, here is a link to a great DIY breakdown. I would consider it to be an intermediate difficulty and expect it to take around 6 hours. Let us know if you have ever done this fix.

Idle Control Valve

The job of the idle control valve is pretty self-explanatory, to be honest. Its job is to regulate the idle speed of the S65 V8. You will know if you have a faulty idle control valve as soon as you turn the car on. Rough start and idle fluctuations are the symptoms of this, plus engine lights and error messages. It will also more than likely put your can into limp mode. Not a fatal issue, but can turn a weekend drive into a headache pretty quickly.

DIY S65 Idle Control Valve Replacement Guide: https://www.m3post.com/forums/showthread.php?p=25287903

S65 Idle Control Valve Failure Symptoms:

• Rough idle
• Irregular idle RPMs
• Hunting or continually fluctuating idle RPMs

Don’t confuse bad spark plugs or ignition coils for a bad idle control valve. A bad control valve will usually be throwing off a check engine light. Additionally, unless your spark plugs are really bad, you will likely only experience a few misfires, rather than a consistently poor idle, although bad gapping can cause this. If your S65 is slow to start, misfires under acceleration, or won’t start in the cold, then it is likely a spark plug and ignition coil issue instead.

Replacement Idle Control Valve: https://www.bmwpartsfactory.com/GENUINE-BMW/9/13-41-7-838-024

Valve Cover and Gasket

Affecting many other BMW engines, this is a typical issue across the board. Owners notice that the gasket leaks a small amount. Some replace just the gasket, others replace both. Keep in mind that this is a high-performance engine that gets hot. Over time, the gasket and the cover tend to warp.  This leads to oil leaks.

Symptoms are oil stains where you park the car, and oil on the engine. It is normal and I would keep an eye on how much oil the engine is consuming and leaving on the ground. If adding oil more than once a month, definitely go get them checked. The gasket is not very expensive, at $180 or so for the gaskets and spark plug tubes. The cover is quite a bit more though at $675 per cylinder bank.

There are DIYs for this one here, and again it is more of an intermediate skill level.

S65 Valve Cover / Gasket Failure Symptoms:

• Oil leaking from the valve cover
• Cracks in the valve cover
• Spark plugs covered in oil
• Smoke coming from the engine due to hot oil leaks

S65 Valve Cover Gasket Replacement Part:

• S65 Cylinder 1-4 Gasket
• S65 Cylinder 5-8 Gasket
• Spark Plug Tube – you need 8 of these if you are doing both gaskets

Make sure you also buy the bank 2 gasket if it is failing as well!

S65 Valve Cover Replacement Part: https://www.bmwpartsfactory.com/GENUINE-BMW/9/11-12-7-848-154

PCV Problems

PCV issues are also common to a wide range of BMW engines and are not specific in any way to the S65 engine. The primary job of the PCV is to alleviate pressure inside of the engine’s crankcase and reroute excess crankcase gasses back to the intake manifold be be burnt off in the combustion chamber. The burning of the excess crankcase gasses helps with emissions, which is why many older BMW engines incorporated them.

The flow of the crankcase gasses through the PCV system is dictated by the PCV valve which is a spring-actuated part that routes gas to a particular area of the intake tract based on pressure. Over time, the spring inside the PCV valve wears out, causing gas and other substances (like oil) to be rerouted to the intake tract. In some cases, a PCV valve failure can cause the engine to start burning oil like crazy.

S65 PCV Valve Failure Symptoms

• Smoke coming from the exhaust
• Timing issues
• Engine running either lean or rich
• New or worsening oil consumption
• Poor engine performance
• Whistling/squealing from the front/rear main seal

Luckily, PCV parts for the S65 are relatively inexpensive plastic components. However, it is pretty difficult to replace some of them, especially the PCV valve, which is located in the rear of the engine behind bank 2. As a result, the wiring harness and other components near the back of the engine will have to be either removed or relocated while you replace it. I couldn’t find an average cost estimate for the job at a dealer, but it would likely be in the $300-$400 range.

S65 PCV Valve Replacement Part: ECSTuning.com

Summary of the 5 Common S65 Engine Problems.

Overall, this engine doesn’t have an overwhelming amount of issues, and I had to dive deep and start nitpicking to get to 5 common problems. The issues it does have are common and known. The S65 is a great engine, the parts are just expensive, as with any M car. The real issue is that the BMW E9X M3 is one of the most expensive BMWs to maintain due to the fact that the common issues that it does have are pretty serious.

Some advice I found from browsing numerous forums.

• Let the car come to temp before you get on it. Don’t rev the engine past 4,500 rpm before it has had time to warm.
• Keep an eye on the oil and change it between 4-6k miles. Check old oil after every oil change. It is also a good idea to have an oil analysis performed every second or third oil change for lead and copper to check the status of your rod bearings.
• Drive it more. Don’t let the car sit for days and weeks. These cars are meant to be driven and driven hard. Enjoy your car, don’t be scared of it.
• Find a service center you trust. This is the case even if you don’t have an M. Good service centers want to help you enjoy your car.
• Have at least $1500 put aside for repairs. It will happen.

Overall, I would consider this to be reliable, but keep in mind what the engine was derived from. It is a performance engine and needs attention. Change out the bearing rods if you’re worried about it, and keep an eye on the oil. This will help ensure a long life for the engine. If you are one who has been looking to jump into a E9X M3 due to them becoming somewhat affordable now, I would say jump on in. Make sure to look over the maintenance records, and do a pre-purchase inspection.

If you are thinking of buying an M3, check out our buyer’s guide.

S65 Reliably Score: 2

1 is the best, 4 is the worst.

Overall there are no huge flaws to the design and with proper maintenance it will run well over 100k miles.  Look at examples here.  One has 190k on it.  It does need attention, and will repairs will be expensive when needed.

What are your thoughts or experiences with the engine?  Let us know.