Need a brief education on timing systems on the Audi V8’s.

[atikovi]

I may be working a deal on a 2005 S4 that will need a timing chain job and understand the engine has to be pulled since the chains face rearward toward the firewall. The RS6 uses a belt but does it face backward too? You also have to pull the engine to replace the belt? And aren’t they the same basic 4.2 engine except for the turbos on the RS6? If so, why the difference? Did the later model S4 and RS4 change to front mounted timing system such that no engine removal is required for parts replacement? If so what years?

[hahnmgh63]

The RS6 has the timing belt in the front. Audi made Mx possible by allowing the front end to tilt outward from the top, called the Service position. The 4.2 in the S4 chassis was a tight fit and Audi shortened the engine slightly by doing the timing chains, and yes they are on the back( they also ended up swapping the timing chain 4.2 in the A8 D3 chassis around 2007). The engine must be pulled to do the timing chains but at least it's not a Turbo car with the extra plumbing. It is easiest to pull the engine & tranny as a package. If it isn't a real high mileage 4.2 the timing chains should be good. The 3.2 V6 is prone to short timing chain life but the 4.2's were much better. Quality oil and regular changes are important to the life of the timing chain also.

[marklar182]

The chain is not usually the issue, its the plastic guides that fail and disintegrate, and cause the infamous chain rattle.

[bethridg]

Visuals are helpful.

B6 and later 4.2 timing chain - more pics (http://redlinespeedworx.com/audi-v8-timing-chain-service-real-story/)

http://redlinespeedworx.com/wp-content/uploads/2014/12/V8_audi_timing_chain_failure_repair_1.jpg

RS6 4.2 timing belt (bumper/core support removed)

http://i.imgur.com/grZVPqfh.jpg

[atikovi]

First pic I assume is the back of the engine? So not only do you have to pull the engine, you have to separate the transmission and remove the clutch and flywheel? What does a full service shop charge for that and doesn't it basically total a 10 year old car?

[mrdave]

Yes that first pic is the rear of the engine. Check out that "more pics" link with more info.

That timing chain is one of the main reasons I ended up with an RS6. I originally started out wanting a B6 S4. Then I found out about that timing chain mess and said, hell why not an RS6? At least I can do the timing belt myself.

And now that I think about it, that's how I got my S6 too. I wanted a 4.2L Allroad but quickly learned it was the timing chain version while the S6 has a nicely accessible belt.

[bethridg]

I just found this MEGA thread over on AZ with some cost estimates

http://www.audizine.com/forum/showthread.php/414598-B6-B7-S4-Timing-Chain-FAQ-Information-Discussion-Thread

[Bigglezworth]

The primary reason I will never own a car with an FSI engine in it. I do difficult mechanics, and even I wouldn't want to piss with the hassle of this - all because of some UHMWP that snaps due to heat stress or wears down from chain friction. A 3hr timing belt service for the cost of parts is just fine for me.

[lswing]

First pic I assume is the back of the engine? So not only do you have to pull the engine, you have to separate the transmission and remove the clutch and flywheel? What does a full service shop charge for that and doesn't it basically total a 10 year old car?

Parts and labor around $7-10k, looked into many times. Yes, that's why these are for sale cheap starting around 75k miles.