Wait, Timing Chain? I Thought These Had a Timing Belt?!
The quick answer is Timing Chain. The B6 & B7 S4 4.2 liter engine utilizes a chain driven timing system which is located on the backside of the engine facing the firewall. So, service position on a B6/B7 S4 does not mean just removing the front clip, it requires engine removal unlike the older 4.2L V8’s found in the A8, A6 etc.
A question you might ask is: If this car doesn’t have a timing belt, doesn’t the chain mean this is maintenance free? Unfortunately, this is not the case. The timing chain itself may never require replacement, however, the other components of the timing system are the weak points.
A Quote Straight From the Audi TSB on This Issue
“The Camshaft Adjustment is hydraulically adjusted and controlled by the engine oil pressure. If the engine has been turned off for a long time, the oil pressure drops down and the oil partially flows back into the oil sump. To ensure an efficient camshaft adjustment right after an engine cold start, the oil pressure inside the camshaft adjusters must be built up as fast as possible. During this time, a rattle or knocking noise may be noticeable. This noise is normal at engine start and will last until the oil pressure is fully built up, which takes about 1-2 seconds. There is no applicable production solution.”
This noise is considered “normal” by Audi and claims this does not necessarily mean that you will need your timing system serviced soon. However, it does hint that your tensioners might be worn and in need of replacement.
Does This Failure Happen to All of the B6/B7 S4’s?
No, but take that answer with a grain of salt. No matter how many problems plague some engines, not all of them suffer from the same failures. No rhyme or reason to it, it’s just the way it is sometimes! When you think of how many S4’s were sold in the era between 2004 and 2007, only a portion of those cars had issues. But we also must come to grips with reality here, nothing lasts forever. So now that these cars have surpassed the decade old age mark, things start to fail because well let’s face it, mechanical items fail. Now, these issues are starting to gain in popularity… and not in a good way.
I Have Heard all the Rumors. Do These Cars Really Have High Dollar Failures at or Even Before 100k Miles?
There is no set mileage where failure is to be expected. We have seen some engines fail in as little as 40-50k miles and others well over 100k miles. There are numerous cars over 140k miles who have had no issues at all. But, are you willing to take that gamble? We have even had customers come to our shop requesting the full timing chain service with the threat of such failures. These owners typically don’t even have a rattle at cold or warm start. The majority of the B6/B7 S4 we have taken apart for this service, rattle or not, have had broken timing chain guides. They are plastic and are resting in a high friction, high heat and high vibration environment. Given these conditions and the guides being made of plastic, you can certainly expect to see cracking.
Tips to Ease the Start-Up Rattle and to Get the Most Out of Your Vital Engine Components
Here are a few tips to help prolong experiencing cold start rattle. You can also take this advice to help increase your chances of avoiding issues all together. Something that we cannot express enough—keeping up with maintenance!
- Frequent Oil Changes: Keeping your engine operating with clean oil is beneficial, but not the complete solution. However, it is merely a piece to the puzzle in keeping your engines timing components in good working condition. This also isn’t going to change the fact that the timing chain guides often crack.
- High Quality Oil: The oil in your motor is like the blood in your veins. We highly recommend using quality oil when servicing your car. The 4.2L V8 in B6 & B7 S4’s use 0w40 or 5w40. A couple popular brands include LiquiMoly and Motul
- Proper Care: If you want the maximum life out of your motor you have to take the necessary steps to take care of it. Allow proper warm up—don’t beat on the car when it is cold and expect it to last forever. Also, keep up with scheduled maintenance and address issues as they arise.
What Should I Expect to Pay?
The cost of having this job done is going to vary. Keep in mind this service is very tedious and involved, and that it should be completed by a mechanic with plenty of experience and who has previously completed the repair. At Excelerate Performance, our mechanics perform at least ten timing chain and guide replacements, if not more, per year.
The motor is out for the Timing Chain Service, what else should I do?
With the motor out of the car, there is an opportunity to take care of maintenance, modifications, and other failing parts that are easier to access with the motor out. By performing these services or modifications while doing the timing chain, you will minimize the labor associated with each respective item. Here are some items to consider when performing the Timing Chain Service:
In addition, all of our timing chain service kits include the Updated Timing Chain Guide. These guides are still plastic but are reinforced with metal for superior longevity and to prevent cracking.
Contribution from Audizine member joeycuccaro and this thread.
Are you the DIY type person and have the tools to do it yourself?
Or are you a shop with the abilities but need the parts?
The link references part number TCK-B6B7S4-JHM