BMW M5 F90 Reliability: The Bulletproof Super-Sedan?
Common Failure Points & Costs
| Component | Failure Mileage | Symptom | Est. Cost (USD) | Risk Level |
|---|---|---|---|---|
| Coolant Expansion Tank | 20k - 40k miles | White residue, low coolant, injector fouling | $600 - $1,500 | High |
| Rear Differential | 10k - 30k miles | Groaning noise in turns | $200 (Fluid Change) / Warranty | Medium |
| High Pressure Fuel Pump | 50k - 70k miles | Long crank, limp mode | $1,200 | Medium |
| Rod Bearings (S63TU4) | 100k+ miles | Rare compared to F10 | $3,000 (Preventive) | Low |
Reliability Verdict
The F90 M5 is arguably the most reliable modern BMW M-car. The S63TU4 engine solved the chronic rod bearing issues of the F10. The main risk is the coolant expansion tank leaking into the injectors/coils, which can cause misfires and damage. Catch that early, and it's a tank.
BMW M5 F90 Reliability: The Bulletproof Super-Sedan?
The F90 BMW M5 (2018-2023) changed the game. It introduced M xDrive (AWD), allowing it to put down its 600+ horsepower without vaporizing tires. But more importantly, it introduced a level of reliability that M5 owners had never seen before.
After the rod-bearing nightmares of the E60 (V10) and F10 (V8), the F90 feels like a Toyota Camry.
But it is still a complex German machine. This guide covers the specific issues of the S63TU4 engine and the F90 chassis.
1. S63TU4: What Did They Fix?
The S63B44T4 is the 4th generation of the S63. BMW finally listened.
- Rod Bearings: The material and clearance were updated. While we still recommend 5k-mile oil changes, the “spun bearing at 60k” panic is largely gone.
- Injectors: Moved to solenoid injectors (more robust than piezo).
- Oiling: A quasi-dry-sump system with scavenger pumps ensures oil pressure even during 1.0G+ cornering.
Is it flawless?
No. But the flaws are “ancillary,” not “catastrophic.”
2. The Big Issue: Coolant Expansion Tank
This is the #1 failure on the F90 M5.
The Problem
The coolant expansion tank sits right on top of the engine banks. It is made of two plastic halves welded together. The seam fails.
The Symptom
- White Crust: Look closely at the tank seams. You will see dried white coolant residue.
- Low Coolant Warning: Occasional top-ups needed.
- Misfires: Danger! If the leak is bad, coolant drips down into the spark plug wells and onto the injectors (Cylinders 5-8). This causes misfires and can corrode the injector wiring harness.
The Fix
- Replace Tank: A new OEM tank is ~$150. Labor is 1-2 hours.
- Upgrade: Aftermarket aluminum tanks (RK Autowerks, Eventuri) solve this permanently.
- Cost: $600 - $1,200 depending on if you damage the coils/injectors.
Advice: Replace the tank proactively every 30,000 miles or upgrade to aluminum immediately.
3. Drivetrain: AWD & Diff
The M xDrive system is brilliant, but complex.
Rear Differential Noise
Some owners report a groaning or rubbing noise from the rear diff during tight low-speed turns.
- Cause: Fluid breakdown or incorrect friction modifier.
- Fix: Fluid flush with the specific BMW MSP/A fluid.
- Cost: $250.
Transfer Case
The transfer case transmits 600hp. It generates heat.
- Service: Change transfer case fluid every 30,000 miles. Do not believe “Lifetime.”
4. Electronics & Brakes
Carbon Ceramic Brakes (CCB)
Optional on the M5.
- Pros: No brake dust, look cool, last 100k miles (if not tracked).
- Cons: $12,000 replacement cost. Squeak loudly when cold.
- Check: Look for chips reliability on the rotor edges. Carbon rotors cannot be turned; they must be replaced.
Steel Brakes
- Cost: Still expensive. Rotors are ~$400 each. Pads are ~$300. Expect a $1,500 brake job every 20-30k miles.
5. F90 vs F10: Is it Worth the Upgrade?
The F90 is significantly more expensive than the F10, but is it worth it?
| Feature | F10 M5 (2012-2016) | F90 M5 (2018-2023) |
|---|---|---|
| Engine | S63TU (Rod Bearing Risk) | S63TU4 (Solid) |
| Drive | RWD (Traction Limited) | AWD (0-60 in 2.8s) |
| Transmission | 7-Speed DCT (Jerky) | 8-Speed ZF Auto (Smooth) |
| Tech | Dated iDrive | Modern CarPlay/Android |
| Reliability | Low | High |
Verdict: The F90 is superior in every metric. It is faster, safer, and critically, it won’t blow up randomly. The F10 is for the brave bargain hunter. The F90 is for the driver who wants one car to do it all.
6. Buying Guide
- LCI vs Pre-LCI: The 2021+ LCI (Life Cycle Impulse) got the larger infotainment screen, updated lights, and critically, revised suspension (M5 Competition) that is much more compliant on the street. Get an LCI if budget permits.
- Verify Coolant Tank: Pop the hood. If you see white crust, negotiate $1,000 off.
- Launch Control: As always, check the launch count. While the ZF8 torque converter is stronger than the DCT clutch, abuse is abuse.
7. Tuning Headroom
The S63TU4 is a monster.
- Stock: 600-625hp.
- Stage 1: 700hp.
- Stage 2: 800hp.
Because the internals are stronger, the F90 handles power much better than the F10. But remember: Tune = Warranty Void. And on an F90, an engine replacement is $30,000.
8. Conclusion
The F90 M5 is a future classic. It combines supercar speed with sedan usability and unexpected reliability.
It proves that BMW can build a reliable V8 if they try hard enough. Just watch that coolant tank.
Expert Buying Advice
Look for a 2021+ LCI (Facelift) for the best tech and suspension tuning. Check the coolant tank for white crust. Listen for rear diff groans. It's a very safe buy.