BMW M5 F90 Engine Problems: Common Issues, Causes, and What Owners Should Know

BMW M5 F90 Engine Problems: What Owners Need to Know

The BMW M5 F90 pairs a twin-turbo V8 with serious performance, but that powertrain can develop issues that matter to daily drivers and enthusiasts alike.

This guide explains the most common BMW M5 F90 engine problems, the warning signs to watch for, and the systems most often involved.

Because the S63 engine is highly stressed and packed with complex electronics, small faults can become expensive quickly.

Knowing the patterns early can help you diagnose problems before they escalate.

What Engine Is in the BMW M5 F90?

The BMW M5 F90 uses the 4.4-liter S63B44T4 twin-turbocharged V8, a member of BMW M division’s S63 engine family.

It combines direct fuel injection, hot-vee turbocharger packaging, Valvetronic, Double VANOS, and extensive cooling and oil control systems to deliver high output.

That architecture supports impressive performance, but it also increases mechanical and thermal complexity.

Compared with a simpler naturally aspirated engine, there are more points of failure, more heat-sensitive parts, and more maintenance-sensitive components.

Most Common BMW M5 F90 Engine Problems

Cooling system leaks and overheating risk

Cooling system problems are among the most important BMW M5 F90 engine problems because the S63 operates under high thermal load.

Common failure points include coolant hoses, plastic fittings, expansion tank components, water pump-related parts, and radiator connections.

Warning signs often include:

• Coolant loss with no obvious puddle
• Sweet smell from the engine bay
• Temperature fluctuations
• Low coolant messages on the iDrive display
• Steam or visible seepage after spirited driving

If coolant levels drop repeatedly, do not ignore the issue.

Overheating can damage gaskets, seals, turbo components, and internal engine parts.

Oil leaks from gaskets and seals

Oil leaks are another well-known problem on high-performance BMW V8 engines.

On the F90 M5, leaks can come from valve cover gaskets, oil filter housing area components, turbo oil lines, and related seals.

Typical symptoms include:

• Burning oil smell after driving
• Oil residue around the engine or undertray
• Smoke from the engine bay if oil contacts hot surfaces
• Gradual oil level decline

Even small leaks should be addressed early.

Oil dripping near hot turbocharger hardware can create odor, mess, and in severe cases fire risk.

Turbocharger wear and boost-related issues

The S63 relies on twin turbochargers, and any turbo-related fault can affect drivability, power delivery, and reliability.

Problems may involve wastegates, boost leaks, charge pipes, vacuum controls, or turbocharger wear over time.

Owners may notice:

• Reduced acceleration
• Uneven or delayed boost
• Check engine lights with boost or charge-pressure codes
• Whining, rattling, or unusual turbo noises
• Smoke under load in some cases

Because the engine is tuned for high performance, even minor boost leaks can feel significant.

Diagnostics should include pressure testing, inspection of vacuum lines, and scanning for BMW-specific fault codes.

Ignition coil and spark plug issues

High-output turbo engines place heavy demands on ignition components.

Spark plugs and ignition coils can wear faster than many owners expect, especially if the car is driven hard, tuned, or maintained on extended intervals.

Common symptoms include:

• Misfires under load
• Rough idle
• Hesitation during acceleration
• Flashing check engine light
• Reduced fuel economy

Misfires should be diagnosed promptly because repeated misfiring can damage catalytic converters and reduce engine performance.

Many owners choose shorter service intervals for plugs than the factory schedule suggests.

Carbon buildup on intake valves

Like many direct-injection engines, the S63 can develop carbon buildup on intake valves over time.

Fuel is injected directly into the combustion chamber, so the intake valves do not get the cleaning effect found on port-injected engines.

Signs of carbon accumulation can include:

• Rough idle
• Cold-start hesitation
• Less responsive throttle
• Gradual loss of smoothness at low RPM

Severe buildup may require walnut blasting or another professional cleaning method.

Frequent short trips can make this issue worse, while regular long-distance driving may help slow it down.

Fuel system faults

Fuel delivery problems can also appear on the BMW M5 F90, especially when components age or the car is modified.

Issues may involve high-pressure fuel pumps, injectors, low-pressure supply components, or related sensors.

Symptoms can include:

• Hard starting
• Engine stumbling during acceleration
• Lean-condition fault codes
• Intermittent power loss
• Fuel smell in rare cases

Because the engine depends on precise fueling under boost, even small fuel delivery problems can trigger drivability issues quickly.

Why Do These Problems Happen?

Most BMW M5 F90 engine problems are tied to heat, pressure, and service demands.

The S63 engine produces large amounts of torque, uses tightly packaged turbocharging hardware, and depends on clean oil, healthy coolant, and strong ignition and fuel systems.

The most common root causes include:

• Long oil change intervals
• Repeated hard driving without proper warm-up and cool-down
• Aging rubber and plastic components exposed to heat
• Carbon buildup from direct injection
• Delayed maintenance on spark plugs, coils, or fluids
• Modifications that increase boost or thermal stress

In many cases, the engine itself is not inherently fragile, but it is sensitive to neglected maintenance and repeated heat cycling.

How Can You Spot Problems Early?

Early detection is the best way to limit repair costs.

BMW’s onboard diagnostics can help, but owners should also pay attention to how the car feels and sounds.

Common early warning signs

• Check engine light or drivetrain malfunction message
• Coolant level warnings
• Oil spots or unexplained oil loss
• Rough idle after startup
• Loss of power or boost
• Unusual ticking, whining, or rattling noises
• Fuel trims or misfire codes during scanning

A quality OBD-II scan tool with BMW-specific capability can reveal hidden fault codes before a dash warning appears.

That is especially useful for intermittent misfires, boost leaks, and sensor faults.

What Maintenance Helps Prevent BMW M5 F90 Engine Problems?

Preventive maintenance is critical for a performance sedan like the M5 F90.

The goal is not just following the factory schedule, but adapting it to the car’s real-world load.

• Change engine oil more frequently than the longest factory interval
• Use the correct BMW-approved oil specification
• Inspect coolant level and hoses regularly
• Replace spark plugs and coils on a sensible preventive schedule
• Allow the engine to reach operating temperature before hard driving
• Use high-quality fuel, especially if the car is tuned
• Check for oil seepage around covers, lines, and filters during service

Owners who track the car or use launch control should be especially disciplined about fluid checks and inspection intervals.

Are Modified M5 F90s More Likely to Have Engine Problems?

Yes, modified cars often face a higher risk of engine-related issues, especially if tuning increases boost or places extra stress on fuel and cooling systems.

Performance software, downpipes, intake changes, and aggressive ethanol blends can improve output, but they may also expose weak points sooner.

Common concerns on modified cars include:

• Higher cylinder pressures and turbo temperatures
• Greater spark plug and ignition demand
• More frequent misfires under load
• Fuel system limitations
• Accelerated wear on seals, hoses, and cooling components

If the car is tuned, maintenance intervals should usually be shortened, and diagnostics should be more frequent.

Supporting hardware matters as much as the tune itself.

When Should You Stop Driving the Car?

Some symptoms are serious enough that the vehicle should be parked until inspected.

Continuing to drive can turn a manageable repair into major engine damage.

Stop driving and seek diagnosis if you notice:

• Persistent overheating
• Heavy coolant loss
• Flashing check engine light with severe misfires
• Loud knocking or metallic engine noise
• Strong fuel smell or visible smoke
• Oil pressure warnings

If the car enters limp mode repeatedly, that is also a sign that a deeper fault may be present.

A qualified BMW specialist with experience on the S63 platform is often the best option for accurate diagnosis and repair planning.

How Expensive Are BMW M5 F90 Engine Repairs?

Costs vary widely depending on the fault, labor rates, and whether the car needs genuine BMW parts or performance-specific components.

Small repairs such as plugs, coils, hoses, or minor gaskets may be manageable, while turbocharger, fuel system, or internal engine work can become expensive quickly.

As a general rule, the most expensive BMW M5 F90 engine problems are the ones that are ignored.

Catching a coolant leak early is far cheaper than repairing overheating damage later.

What Should a Prospective Buyer Check Before Buying Used?

If you are shopping for a used F90 M5, prioritize inspection over appearance.

A clean exterior does not guarantee a healthy S63 engine.

• Verify service records and oil change frequency
• Check coolant condition and look for residue around fittings
• Inspect for oil leaks under the engine cover and beneath the car
• Scan for stored and pending fault codes
• Test for smooth idle and strong, consistent boost
• Listen for cold-start noise and turbo-related sounds
• Ask whether the car has been tuned or tracked

A pre-purchase inspection from a BMW specialist can reveal issues that are easy to miss during a short test drive.