BMW 120D N47 Timing Chain Replacement – Engine Out Job

Real BMW 120D N47 Timing Chain Replacement Case Study

This is a detailed walkthrough of a BMW 120D N47 timing chain replacement we completed at Star Garage Mansfield. The job required an engine-out approach due to the extent of wear and damage. Below, you’ll find the full process, exact costs, timeline, and what we replaced.

For general N47 timing chain information, symptoms, repair options, and affected models, see our complete BMW N47 timing chain guide.

The Big Job: BMW 120D N47 Timing Chain Failure

When a 120D comes into the workshop with chain noise, we know what’s coming — and it usually means a full engine-out job. That’s exactly what we tackled this week with this BMW 120D powered by the infamous N47 engine.

Common Failure on N47 Engines

The N47 engine is known throughout the trade for its rear-mounted timing chain. Over time, the chain stretches, the tensioners weaken, and a distinct rattle or ticking noise starts — particularly on cold starts.

The problem is, the chain is mounted at the back of the engine, making access impossible without removing the engine completely. It’s a poor design from BMW that turns a chain replacement into one of the most time-consuming jobs on any diesel car.

Why Engine-Out Is Necessary for N47:

• Timing chain located at rear of engine (not front like most cars)
• Chain cover cannot be accessed without full engine removal
• Allows for complete inspection of guides, tensioner, and gears
• Opportunity to service clutch, flywheel, and oil pickup while engine is out
• Ensures proper reassembly and timing verification

What the BMW 120D N47 Engine-Out Job Involves

This is a big job and the price reflects the labour, not just the parts. Here is what it takes in:

Why This Cost?

• Labour-intensive: 35 hours of skilled work (engine removal, inspection, replacement, reassembly)
• Parts quality: OEM-spec components ensure reliability and longevity
• Comprehensive: Includes inspection of clutch, flywheel, oil pickup, and sump cleaning
• Professional standards: Proper timing verification, testing, and 12-month warranty

Cost Comparison: For a full breakdown of engine-in vs engine-out repairs and other options, see our N47 timing chain cost guide.

Engine Removed for Proper Access

Once the customer gave the go-ahead, we began the process of pulling the engine. It’s a big job: fluids drained, wiring and mounts disconnected, and the whole unit dropped out for access to the chain cover.

We always photograph and label everything during strip-down to ensure a clean reassembly later. It’s these details that matter when you’re putting an engine back together properly.

Why Is BMW 120D N47 Timing Chain Replacement an Engine-Out Job?

The N47 engine design requires the engine to be removed from the vehicle to safely access the timing chain. Here’s why:

• Limited Access: The timing chain is located deep inside the engine block, behind the crankshaft and camshaft.
• Gearbox Interference: The gearbox must be disconnected to create enough space for engine removal.
• Safety & Precision: Engine-out access allows our technicians to inspect the entire engine, check for oil sludge, and perform a thorough repair.
• Prevention of Further Damage: Removing the engine prevents accidental damage to other components during the repair.

At Star Garage Mansfield, we use specialist equipment and have years of experience with N47 engine-out jobs. We work efficiently to minimize downtime while ensuring quality workmanship.

Engine Removal Process:

1. Drain all fluids (oil, coolant, fuel)
2. Disconnect all wiring harnesses and sensors
3. Remove engine mounts and ancillaries
4. Lift engine out using engine hoist
5. Remove timing chain cover
6. Inspect for damage and wear

Timing Chain Kit Replacement

With the engine out and cover removed, it was clear the chain had started to score the guide rail — a clear sign of stretch. We installed a full OEM-spec timing chain kit, including:

• Primary and secondary timing chains
• New guides and tensioners
• Crankshaft gear and upper cam gear
• Fresh gaskets and seals

We also cleaned the oil pickup and sump while the engine was out, to remove any debris from worn chain material.

What We Found:

• Chain had stretched approximately 5mm (normal wear is 2–3mm)
• Upper guide rail showed scoring marks from chain contact
• Tensioner spring had weakened, causing slack
• Oil pickup screen had accumulated chain debris

All components were replaced with OEM-spec parts to BMW standards.

Rebuild and Refit

After the new chain was fitted and timing verified with locking tools, the engine was reassembled and refitted into the bay. All fluids were replaced and the system bled before starting the car for the first time.

The result? No more rattle, no more error codes, and a smooth, responsive drive once again.

Post-Repair Testing:

• Engine start-up (cold and warm)
• Diagnostic scan for fault codes
• Oil pressure check
• Road test for performance and noise
• Final inspection and sign-off

Timeline: How Long Did This Repair Take?

Stage	Time	Details
Diagnostics & Inspection	2 hours	Initial scan, visual inspection, quote preparation
Engine Removal	6 hours	Drain fluids, disconnect wiring, remove mounts, lift out
Chain Replacement	12 hours	Remove cover, replace chain/guides/tensioner, verify timing
Engine Reassembly	10 hours	Reassemble, refit into bay, reconnect all systems
Testing & Sign-Off	3 hours	Start-up, diagnostics, road test, final inspection
TOTAL	33 hours	Completed in 4 days (including diagnostics)

BMW 120D N47 Timing Chain Replacement FAQs

How much does BMW 120D timing chain replacement cost?

The N47 timing chain replacement is a fixed £2,200 + VAT. If the chain has already failed and there is damage beyond the chain itself, we price that on the day, because it depends on what we find and on what parts we can get hold of that week. For a full cost comparison, see our N47 timing chain cost guide.

How long does 120D timing chain replacement take?

Engine-out repairs take 30–45 hours of labour, typically 3–5 days in the workshop including diagnostics, removal, replacement, reassembly, and road testing. This case study took 33 hours over 4 days.

Can you replace BMW 120D timing chain without removing engine?

In most cases, no. The N47 timing chain is located at the back of the engine, making engine-in replacement extremely difficult and unreliable. Engine-out is the recommended approach for thorough inspection and proper repair. It ensures the job is done right and prevents future failures.

What’s included in BMW 120D timing chain replacement?

Full replacement includes: main timing chain, upper and lower guides, tensioner, crankshaft and camshaft gears (if damaged), all gaskets and seals, fresh oil and filter, and 12-month warranty on parts and labour. Additional services like clutch inspection and oil pickup cleaning are often included while the engine is out.

Why is N47 timing chain replacement so expensive?

The high cost is due to: (1) Labour-intensive removal (6+ hours just to get the engine out), (2) Complex reassembly requiring BMW-specific tools and expertise, (3) Quality parts (OEM-spec components ensure reliability), (4) Comprehensive inspection while the engine is accessible, and (5) Professional standards including testing and warranty.

Own a BMW with the N47 Engine?

If your 1 Series, 3 Series, X1, or other N47-equipped BMW is hearing unusual noises from the engine — especially on cold starts — don’t wait. Timing chain failure can lead to catastrophic damage if it goes unchecked.

Catching it early keeps you on the fixed-price chain job rather than an open-ended repair bill.

At Star Garage Mansfield, we’ve completed multiple N47 chain replacements and know exactly what’s involved. We take the time to do the job right, using high-quality parts and professional care from start to finish.

Next Steps:

• Read our complete N47 timing chain guide for symptoms, affected models, and repair options
• View our timing chain services
• Engine removal and repair services
• Book a free N47 inspection – Call 01623 904724

Need Help? Book In Today

If your BMW is rattling on cold starts or you’re concerned about timing chain failure, book a free inspection today. We’ll diagnose the problem, explain your options, and provide an honest quote with no obligation.

Call 01623 904724
Star Garage Mansfield, NG19 9LF
Monday–Friday: 8:00 AM–5:30 PM | Saturday: 8:00 AM–1:00 PM | Sunday: Closed

Or book online: Request a free N47 inspection