The Audi B6 and B7 S4 models, known for their powerful 4.2-liter V8 engines, utilize a timing chain system. This article serves as a comprehensive guide to understanding the Audi S4 Timing Chain system, common issues, maintenance, and repair options. Whether you’re a current owner or considering purchasing a B6/B7 S4, this information is crucial for maintaining your vehicle’s performance and longevity.
Timing Chain vs. Timing Belt: What’s in Your Audi S4?
To clarify, the Audi B6/B7 S4 is equipped with a timing chain, not a timing belt. While some 4.2-liter V8 variations use timing belts (like those found in the C5 A6 4.2), the S4’s engine specifically employs a more durable chain-driven system.
Location of the Audi S4 Timing Chain System
Unlike timing belt systems typically located at the front of the engine, the audi s4 timing chain system is positioned at the rear of the engine, facing the firewall. This rear placement significantly impacts accessibility and maintenance procedures.
Audi S4 V8 Engine Diagram
Common Misconceptions: It’s Not Always the Chain Itself
When discussing failures within the audi s4 timing chain system, it’s important to understand that the chain itself rarely snaps. Instead, problems usually arise from the wear and tear or breakage of related components. The most common culprits are:
- Cam Adjusters: These components control camshaft timing and can develop issues over time.
- Chain Tensioners: Hydraulic tensioners maintain proper chain tension and are prone to wear or failure.
- Chain Guides: These plastic guides direct the timing chain and can break or wear down, leading to chain slack and noise.
The Infamous Cold Start Rattle in Audi S4 Engines
A common concern among Audi S4 owners is a rattling noise during cold starts. According to Audi’s Technical Service Bulletin (TSB), this cold start rattle is often considered “normal” to a degree. Here’s why:
The camshaft adjustment in the 4.2 V8 is hydraulically controlled by engine oil pressure. When the engine is off for an extended period, oil pressure decreases, and oil can drain from the camshaft adjusters. Upon cold start, it takes a few seconds for oil pressure to build up sufficiently within the adjusters. During this brief period, a rattle or knocking noise may be audible. Audi states this noise should typically last only 1-2 seconds until oil pressure is fully restored.
While Audi considers this brief rattle normal, persistent or worsening rattle, especially beyond a couple of seconds, could indicate wear in the tensioners or other timing components. It’s a signal to pay closer attention to your audi s4 timing chain system’s health.
Tips to Minimize Start-up Rattle and Prolong Timing Component Life
While you can’t entirely prevent wear, certain maintenance practices can help reduce start-up rattle and potentially extend the lifespan of your audi s4 timing chain components:
- Frequent Oil Changes: Many Audi S4 enthusiasts recommend oil changes every 3,000-5,000 miles. Sticking to a more frequent schedule than the factory recommendation can help reduce wear on chain guides, though it won’t prevent eventual component failure.
- High-Quality Engine Oil: Using premium engine oil of the correct viscosity (0W40 or 5W40) is crucial. Brands like Mobile 1, Lubro Moly, and Motul are popular choices among Audi owners. Quality oil ensures optimal lubrication and protection for all engine parts, including the audi s4 timing chain system.
- Proper Vehicle Care: Treat your S4 with care. Allow the engine to warm up properly before demanding high performance. Avoid aggressive driving when the engine is cold. Regular scheduled maintenance and prompt attention to any emerging issues are key to maximizing the lifespan of your engine and its components.
Is Timing Chain Failure Inevitable in All Audi B6/B7 S4s?
No, audi s4 timing chain failure is not a universal issue across all B6/B7 S4s. While it’s a known potential problem, only a relatively small percentage of these vehicles experience catastrophic timing-related failures requiring major service. However, due to the potential cost and complexity of repairs, it’s a factor to consider when owning or purchasing one of these cars.
The 100,000 Mile Myth: Timing Chain Failure Mileage
There’s no definitive mileage marker for when audi s4 timing chain component failure becomes inevitable. Failures are case-by-case. Some engines may experience issues as early as 40,000-50,000 miles, while others exceed 140,000 miles without problems. Polls and anecdotal evidence suggest that the average mileage for timing component issues tends to cluster around the 100,000-mile mark.
Therefore, if you’re considering an Audi S4 with around 100,000 miles, it’s wise to be aware of the potential for audi s4 timing chain related maintenance in the future. It doesn’t mean failure is imminent, but it’s a factor to keep in mind.
Symptoms and Diagnostic Codes Indicating Potential Timing Chain Issues
Recognizing the symptoms of potential audi s4 timing chain problems is crucial for timely intervention. Here are common indicators:
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Cam Over-Advance Codes: Fault codes related to “Cam Over-Advance” often point specifically to issues with the cam adjusters. In these cases, replacing just the cam adjusters might be sufficient and can sometimes be done without removing the engine from the car. Access is tight, but experienced mechanics can replace them by removing the rear timing covers while the engine remains in the vehicle.
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Persistent or Worsening Start-up Rattle: As mentioned, a brief cold start rattle can be considered normal. However, if the rattle becomes louder, lasts longer than a couple of seconds, or occurs more frequently, it’s a stronger indication of wear in tensioners or adjusters. Possible causes include worn tensioners or failing adjusters.
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Misfires and Reduced Performance: Experiencing engine misfires and a noticeable decrease in performance can signal a more advanced stage of timing component wear. This suggests the issue is progressing and requires attention soon. Possible causes include failing tensioners or failing adjusters.
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Limp Mode: If your Audi S4 enters limp mode (reduced power and engine malfunction warning lights), this signifies a serious problem demanding immediate attention. Stop driving immediately and have the car towed to a qualified repair shop or dealership. Continuing to drive in limp mode can lead to further engine damage. Possible causes: broken tensioner, broken adjuster, or broken tensioner guide.
If you observe any of these symptoms, it’s essential to seek professional diagnosis to pinpoint the exact issue within your audi s4 timing chain system.
Visual Evidence of Timing Component Failure
Here are visual examples of damaged timing components commonly found in Audi S4 4.2 V8 engines:
Audi S4 Timing Chain Service and Replacement
Engine Removal: Is it Necessary for Timing Chain Service?
For a comprehensive audi s4 timing chain service, including replacing chains, tensioners, and guides, engine removal is generally required. Due to the rear location of the timing chain system, accessing it for extensive repairs is virtually impossible with the engine in the car.
However, as mentioned earlier, in some cases where only cam adjusters need replacement, it might be possible to perform the repair with the engine still in the vehicle.
DIY Timing Chain Replacement: Is it Possible?
Yes, a DIY approach to audi s4 timing chain replacement is possible for experienced mechanics. However, it’s a complex and time-consuming job, definitely not a weekend project for beginners. Plan for it to take significantly longer than a weekend, even with assistance.
Resources for DIYers:
- Engine Pull DIY Guide: ENGINE PULL DIY (Note: Link may be outdated, research current forums for up-to-date guides).
- Cam Adjuster Replacement Video (Bank 2): Replacing the Bank 2 Cam Adjuster VIDEO (YouTube).
Essential Tools for DIY Timing Chain Service:
- Crank holder / Pin
- Trim Wedges
- Multi-point Socket Set
- Camshaft Locators
- Setting Gauge
Specialty tool kits for audi s4 timing chain service can be purchased or rented from automotive specialty tool suppliers. HERE & HERE
Cost of Parts for Audi S4 Timing Chain Overhaul
The cost of parts for an audi s4 timing chain overhaul can vary based on what components need replacement. Here’s an estimated parts list for a complete overhaul:
Essential Parts:
- Cam Adjuster: (079109087N) [2]
- Cam Adjuster Bolt: (N91086201) [2]
- Control Housing (Bank 1): (079109210H)
- Control Housing (Bank 2): (079109204L)
- Control Housing Gasket (Bank 1): (079109092B)
- Control Housing Gasket (Bank 2): (079109091B)
- Chain Tensioner (Bank 1): (079109218D)
- Chain Tensioner (Bank 2): (079109217J)
- Tensioner Chain Guide (Bank 1): (079109510E)
- Chain Guide (Bank 1): (079109514B)
- Chain Guide (Bank 2): (079109513C)
- Center Upper Chain Guide: (079109469AD)
- Left Lower Chain Guide: (079109469AA)
- Left Lower Chain Guide: (079109510F)
- Lower Chain Tensioner/Guide assembly: (079109507G)
- Lower Chain Tensioner: (079109467AE)
- Cam Position Sensor (Bank 1 & 2): (06E905163) [2]
- Hydraulic Controller Seal: (079109293C) [2]
- Coolant/SAP Gasket: (079131120A)
- Center Lower Gasket: (079109139A)
- Kombi Valve Gasket (Pipe 2 timing cover): (079131120B)
- Kombi Valve Gasket (Valve 2 valve): (078131120K)
- Diamond Disc Washer: (079105193) [2]
- Fuel Injector Seal Set [8]: (035906149A)
- Intake Manifold Gaskets [2]: (077129717Q)
- Valve Cover Gasket Kit (Bank 1: 1-4): (077198025B)
- Valve Cover Gasket Kit (Bank 2: 5-8): (077198025C)
- Oil Filter Housing Seal (Double O-Ring): (079115111A)
- Oil Filter Housing Seal (single O-Ring): (N90959701)
- Rear Water Manifold O-Rings [2]
Optional Chains (Consider replacing during major service):
- Timing Chain Center Upper: (079109229)
- Timing Chain Center Lower: (079109229D)
- Timing Chain Upper Left: (079109229K)
- Timing Chain Upper Right: (079109229L)
Estimated Parts Cost:
- Complete Overhaul (with Cam Adjusters): Slightly above $3,000 (USD)
- Overhaul (without Cam Adjusters): Approximately $2,000 (USD)
These prices are for parts only and do not include labor or special tools.
Shop or Dealership Service for Audi S4 Timing Chain
Labor Costs for Professional Service:
Labor costs for audi s4 timing chain service vary significantly depending on location and shop labor rates. Quotes can range from $5,000 to over $10,000 (USD). It’s crucial to get quotes from experienced independent Audi specialists or Audi dealerships with proven experience in this specific repair. This is a complex and critical service that requires expertise to avoid costly errors.
Used Engine Replacement vs. Timing Chain Service?
In some cases, the cost of audi s4 timing chain service might approach or even exceed the cost of a used engine. While a used engine might seem like a cheaper alternative initially, consider these points:
- Unknown History of Used Engine: A used engine may also have timing chain components nearing the end of their lifespan, potentially leading to future issues.
- Peace of Mind with New Components: Investing in timing chain service provides peace of mind knowing that critical components are new and properly installed.
If considering a used engine, insist on leak-down and compression tests to assess its internal health. Look for engines with lower mileage and ideally some form of warranty.
Additional Maintenance to Consider During Engine Removal
Since engine removal is a significant undertaking, it’s wise to address other maintenance items or upgrades while the engine is out of the car. This can save labor costs in the long run. Consider these items:
Maintenance:
- Clutch and Flywheel (if manual transmission)
- Motor Mounts
- Engine Accessories (Starter, Alternator, Power Steering Pump, AC Compressor)
- Serpentine Belt
- Valve Cover Gaskets (even if replaced during timing service, double-check)
- Spark Plugs
Performance Modifications (Optional):
- Performance Headers / Downpipes
- Upgraded Intake Manifold / Spacers
- Oil Cooler Kit
- Lightweight Crank Pulley
- Snub Mount Upgrade
- Performance Shifter Components
By addressing these items during the audi s4 timing chain service, you can proactively maintain your vehicle and potentially enhance its performance.
Disclaimer: This information is for general guidance only and should not be considered professional automotive advice. Consult with a qualified mechanic for diagnosis and repair recommendations specific to your vehicle. Always refer to your vehicle’s service manual and follow safety precautions when performing any automotive work.
