The BMW N47 and N57 Timing Chain: Why It Stretches, How to Diagnose It, and When to Replace It

Quick Summary

The BMW N47 and N57 diesels carry a built-in weakness—the timing chain sits on the transmission side, which makes access difficult. On early N47 versions (2007–2011), the chain can snap before 62,000 miles. The main culprits are worn plastic guides and a failing tensioner. You can diagnose the problem without removing the transmission, but replacement requires dropping it. This guide is for owners and buyers of used BMWs with these engines.

The Problem

You get into the car on a cold morning, start the diesel—and hear a metallic knock from the transmission side. That’s the classic sign of a stretched timing chain on an N47 or N57. Unlike most engines, where the chain sits up front, here it’s hidden behind the flywheel. The only way in is to remove the transmission, and the job takes 12–20 hours of labor. On early N47 engines (2007–2011), chains have snapped before 62,000 miles—abnormal for a chain that’s supposed to last the life of the engine.

Symptoms

• Metallic knock or rattle on cold starts, lasting 10–30 seconds
• Fault codes 2A82 and 2A87—camshaft timing correlation faults
• Metal shavings on the magnetic drain plug or in the oil filter
• High oil consumption
• Noise from the transmission side at idle

Causes

Worn guides and tensioner. The plastic guide shoes lose elasticity over time, crack, and crumble. Once the guides wear, the chain starts to slop around, which accelerates stretching. The hydraulic tensioner can also stick or stop holding tension when contaminated oil gets into it.

Operating conditions. Stop-and-go city driving with constant starts and stops puts cyclic loads on the chain. Mileages above 93,000 miles and city use speed up the wear. On highway cars with steady loads, the chain lasts noticeably longer.

Inadequate lubrication. On a cold start, thick oil reaches the tensioner and guides slowly. Rev the engine hard right away and the chain runs oil-starved. Infrequent oil changes make things worse: dirty oil lubricates the timing components poorly.

The Fix

Diagnosis Without Removing the Transmission

1. Listening. Start the engine and put your ear—or a stethoscope—near the flywheel area. Any noise that doesn’t belong points to chain or guide wear.
2. Borescope inspection. A technician removes the camshaft sensor and feeds a borescope into the opening—this gives a visual read on the chain and guides.
3. Fault scan. Read the camshaft timing codes. Even if no warning light is on, a code may be stored in the DME memory.
4. Oil check. Pull the oil filler cap and shine a flashlight inside—glittering particles mean wear.

Chain Replacement

Replacing the chain means removing the transmission—the chain lives on the flywheel side. Labor time runs 12–20 hours (versus 4–6 hours on a conventional engine). The recommended replacement point is after 62,000 miles or at the first symptoms. If you’ve bought a used BMW with over 62,000 miles and no service history, chain replacement should jump to the top of your list.

When you replace the chain, always check the oil pump, especially if shavings turned up in the oil. Metal particles may have reached the oil galleries and damaged the crankshaft and camshaft bearings. If there’s debris in the system, plan on flushing it and replacing the oil pump.

Prevention

• Oil changes every 6,000–9,000 miles; in city driving, every 6,000 miles
• Use only BMW Longlife-04 5W30 oil
• After a cold start, give the oil 20–30 seconds to circulate, and keep revs under 2,000–2,500 rpm for the first 5–10 minutes
• Check the oil level monthly
• After 62,000 miles, have the chain inspected every 12,000–19,000 miles

Used BMW N47/N57 Pre-Purchase Checklist

• Witness a morning cold start—listen for a knock from the transmission side
• Scan for 2A82 and 2A87 codes—a direct sign of chain trouble
• Inspect the oil for metal shavings
• Gauge oil consumption: more than 0.5 liter per 1,000 miles is a red flag
• Ask for service records: regular oil changes every 9,000 miles is a good sign

The Bottom Line

The timing chain is the known weak spot on the N47 and N57, and it demands attention past 62,000 miles. The main thing: don’t ignore a cold-start knock or 2A82/2A87 codes. Timely diagnosis without dropping the transmission—listening, borescope, oil check—catches the problem before the chain lets go. Regular oil changes every 6,000–9,000 miles with Longlife-04 5W30 are the most effective way to extend the chain’s life. And if you’re shopping for a used BMW with an N47/N57, always check the cold start, the codes, and the oil consumption.