Audi S5 4.2, need to know common issues!
 

Thinking of buying 2008-2009 Audi S5 4.2 V8, not sure if manual or auto yet. Currently i got a 3.2 Audi A6, so i wonder if this engine is basically the same thing, except the extra 2 cylinders.

What common problems/issues are there that i should be aware of?

Is the 4.2 still as fragile chain tensioner vise as 3.2?

Also i've read about the manual clutch issue it has? How much does it cost to fix it if it happens to have it at some point. What else could there be? Any other issues?

cant comment on common issues except some face rattle/vibration problems and some do not.

for clutch replacement youd be looking at 800-1300, and for some shops thats labor only.

I did the clutch on my old car which was a b6 1.8t, and this was my first time doing a longitudinal motor/trans setup(ive done FWD/transverse setups before) and it is time consuming to say the least. i have a feeling that when/if i do it to my A5 i will pull the motor and trans out to do it..

Anecdotally there seemed to be a rash of clutch issues on the 08's and early 09's, though personally I have not had any issues at all with my transmission or clutch.

One common issue is carbon build up in the direct fuel injection engine, which often requires a cleaning of the engine valves at around 40-50K miles. Other than that many of us have experienced random issues of things like headlight control modules and side assist module having to be replaced. Also the finish on the engine Start/Stop button may begin to flake off after 4-5 years - it is on mine. To make it look new again means replacing the entire start/stop switch.

I have to chuckle at your question as to whether a 4.2L V8 is "the same thing" as a 3.2L V6. No, they're not the same. Obviously the 2 extra cylinders and larger displacement results in significantly more peak HP and torque than what you had with the 3.2L. Also, depending on the year of your A6 the 3.2L may not have been direct injection.

The 3.2 is 2004 year and it's FSI, so far i've understood that its exactly the same thing as 4.2 technical wise? I'm not saying 3.2 is comparable to 4.2 performance wise.

I'm interested in the engine issues, have they made 4.2 any way better or its just 2 cylinder extension of 3.2? By better i mean tehnical way, like resolved the chain tensioner issues etc. I have to say 3.2 is pretty much a failure engine in my opinion, everything about the Audi is nice except the engine problems, i just hope they have changed something and i wouldn't have to visit my technician as often as i do in the V6.

As i see carbon buildup is still a major problem after 4 years of audi engineering...

I believe Audi made some changes in the 3.2L V6 back in 2007 at least in part to resolve the chain tensioner issue. I have not heard of any issues like that on the 4.2L engine used on the S5 pre-facelift cars from 2007 - 2011.

I have a 2009 S5, I have had nothing but problems. I bought the car in April 2017 and have had low fuel pressure issues.
I have changed the low pressure fuel pump, both high pressure fuel pumps, low & high pressure sensors, PCV valve, exhaust and
still have the issue.

I purchased my 09 S5 4.2L with 99k on the clock. Below is the list of what I have repaired on my S5, keep in mind this one WELL maintained by the previous owner. I now have 130k miles and she runs like a champ. I did all this work over a period of time. The first thing I replaced were the control arms. If you test drive one and there is a steering wheel shake between 60 to 70 mph, there's a good chance the bushings are shot. I would take a bottle of water and pour a little water in each corner of the moonroof. The front two drains should drain to a point directly under the respective door hinge. The rear two drain to a point directly over the rear wheel wells. just look for a wet spot to form on the top of the wheel wells looking up from the inside.

Engine:
Fix Oil Filter Housing Gasket Leak
Replaced Serpentine Belt (It was the original, Should have been replaced @ 60K)
Replaced Spark Plugs
Carbon Cleaned (for the first time)
Battery Replaced 3 weeks ago (Original Battery, build date 11/08)

Suspension:
Replaced ALL front Upper and lower Control Arms (Bushings were shot. Common problem with these cars)

Transmission:
Fixed Electrical Connector Seals causing the transmission to leak

Moonroof:
Repaired the front drivers side drain hose causing a leak into the cabin

Moonroof
 

How did you repair the driver side moonroof I am having the same issue

Requires removing some interior bits, there is apparently a drain fitting that breaks.