1995 BMW 740i M60 Crankshaft: Forged Strength, Failure Signs & Buying Guide
Learn to distinguish true crankshaft failure from common sensor issues and what to inspect on a used M60B40 crankshaft before you buy.
- This crankshaft is for the 4.0L M60B40 engine ONLY and is not compatible with the 4.4L M62 engine from 1996+ models.
- Before installing a used crankshaft, it is MANDATORY to have it inspected and measured by a machine shop to verify it is straight and within size specifications (70mm main/48mm rod).
- Symptoms like 'crank-no-start' are almost always a bad Crankshaft Position Sensor, not the crankshaft itself. True mechanical failure involves loud knocking and metal in the oil.
- Crankshaft replacement is an engine-out job with very high labor costs; swapping the entire engine is often a more economical repair.
Is It Your Crankshaft or Just a Sensor?
Many symptoms that seem like catastrophic engine failure on a 1995 BMW 740i are actually caused by a faulty Crankshaft Position Sensor (CKP), not the crankshaft itself. A bad sensor is a common, relatively inexpensive fix, while a bad crankshaft is a major, engine-ending problem. Understanding the difference is the first step in any diagnosis.
- Crankshaft Position Sensor Failure Symptoms: The engine cranks but won't start, the car stalls suddenly while driving, it has a long crank time before starting, or the tachometer doesn't move while cranking. The engine's computer (DME) loses the signal telling it the engine is turning, so it cuts fuel and spark as a safety measure. This will often store a fault code like P0335.
- Mechanical Crankshaft Failure Symptoms: These are much more violent and physical. They include a deep, rhythmic knocking or clunking sound from the bottom of the engine, severe vibrations that increase with RPM, and visible metal shavings in the engine oil.
Pro Tip: If your car cranks but won't start, and you don't hear any loud knocking noises, your first suspect should be the crankshaft position sensor, not the crankshaft itself. Checking for fault codes is the fastest way to diagnose a sensor issue.
Symptoms of Mechanical Crankshaft Failure
If you have ruled out a sensor issue, the signs of a physically damaged crankshaft are severe and should not be ignored. Driving with these symptoms will lead to catastrophic engine failure.
- Deep Engine Knock: This is the most common sign. A worn crankshaft journal or a failed connecting rod bearing creates excessive clearance, causing a heavy, metallic knocking sound from the lower part of the engine. The noise is distinct from a lighter valvetrain tick and typically gets louder and faster as engine speed increases.
- Excessive Vibration: A bent or out-of-balance crankshaft will cause a significant vibration throughout the car. This is not a subtle shake but a harsh shudder that you can feel in the steering wheel and seats.
- Metal Shavings in Oil: When you drain the engine oil, it may look like it has glitter in it. These are fine metal particles from the destroyed bearings and crankshaft journals. This is a definitive sign of severe internal engine damage.
- Low or Fluctuating Oil Pressure: Worn bearings increase the clearance around the crankshaft, causing a significant drop in oil pressure. The oil pressure warning light may flicker or stay on.
- Seized Engine: In the final stage of failure, the crankshaft will seize, and the engine will lock up completely. It will not be able to turn over at all.
Buying a Used 1995 740i Crankshaft
Because a new OEM crankshaft is often unavailable or prohibitively expensive, a high-quality used OEM part is the most practical option. The M60B40's forged steel crankshaft is a durable component, and a good used one can provide excellent service if inspected properly.
Physical Inspection Checklist:
- Check Journals for Scoring: Run your fingernail across all main and rod bearing journals. You should not be able to feel any grooves or scratches. The surfaces must be perfectly smooth.
- Look for Heat Discoloration: Blue or dark brown discoloration on the journals is a sign of overheating due to oil starvation. Avoid any crankshaft with these marks.
- Inspect for Cracks: Carefully check the areas around the oiling holes and where the journals meet the counterweights. Any visible crack means the crankshaft is junk.
- Verify Part Numbers: Confirm the part is a genuine BMW M60 crankshaft. Look for OEM part numbers like 11211729087 or 11211729261.
Machine Shop Verification (Mandatory):
A visual inspection is not enough. Before installation, you MUST take the used crankshaft to a reputable automotive machine shop for professional measurement.
Warning: Do not install a used crankshaft without having it professionally measured. Failure to do so will likely result in immediate engine failure. The required journal dimensions are 70mm for the main bearings and 48mm for the rod bearings.
The machine shop should:
- Measure Journal Diameter and Roundness: Using a micrometer, they will confirm the journals are within BMW's specified tolerances and are not worn into an oval shape.
- Check for Straightness: They will mount the crank on V-blocks and use a dial indicator to ensure it is not bent.
- Polish the Journals: It is standard practice to have the journals micro-polished to ensure a perfect surface for the new bearings.
Compatibility Warning: This crankshaft fits ONLY the 4.0L M60B40 V8 engine used in the 1995 740i and other contemporary models like the 540i and 840i. It will NOT fit the later 4.4L M62 engine found in 1996 and newer models. The M62 uses a different stroke and design.
Cost to Replace a 1995 740i Crankshaft
Replacing a crankshaft is one of the most labor-intensive repairs possible and is often not economically viable. The entire engine must be removed from the vehicle and completely disassembled. Because of the high labor cost, replacing the entire engine with a known-good used unit is often a more practical and cost-effective solution.
| Part/Service | Estimated Cost | Notes |
|---|---|---|
| New OEM Crankshaft | $2,500+ (if available) | Extremely rare and expensive. Often no longer available from BMW. |
| New Aftermarket Crankshaft | Not Generally Available | The market for new aftermarket M60 cranks is virtually non-existent. |
| Used OEM Crankshaft | $150 - $400 | This is for the part only and requires machine shop verification. |
| Shop Labor | $2,000 - $3,500+ | Includes engine removal, disassembly, reassembly, and installation. Can take 16+ hours. |
| Complete Used Engine | $800 - $2,000 | Often a more economical alternative to a full crankshaft replacement. |
Frequently Asked Questions (FAQ)
Can I use a crankshaft from a newer 4.4L M62 engine in my 4.0L M60?
No, you cannot. The M62 engine has a different stroke (82.7mm vs. the M60's 80mm), which means the crankshafts are not interchangeable. You must use a crankshaft specifically from an M60B40 engine.
What causes a crankshaft to fail?
The most common causes are oil starvation from a failed oil pump or low oil level, and bearing failure from old age or contamination. Aggressive driving on a high-mileage engine or an improper engine assembly can also lead to fatigue and failure.
Is it worth replacing just the crankshaft?
For most owners, no. The labor cost to replace only the crankshaft is so high that it usually makes more financial sense to replace the entire engine with a good used one. A crankshaft-only replacement is typically reserved for full engine rebuilds or performance applications.
Are there any recalls for the 1995 740i crankshaft?
No. There are no NHTSA recalls or manufacturer service campaigns related to the crankshaft for the 1995 BMW 740i.
Technical Specifications
OEM Part Numbers: 11211729087 11211729261
Construction: Forged Steel Engine: 4.0L M60B40 V8 Main Bearing Journal Diameter: 70mm Rod Bearing Journal Diameter: 48mm
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- BMW 740i: