In this post I will be giving a look at the inner workings of the timing system on the 4.2L BAS code Audi V8. This engine was commonly found in the Audi allroad in 2004 and 2005 as well as other V8 Audis. This was the first generation of the 4.2L V8 with timing chains as opposed to a timing belt. Of course timing chains have the advantage of longer service life than the timing belt, but when they need changed, you find that
they are conveniently located on the rear of the engine between the engine and transmission. This requires removal of the engine and transmission to access the chains. This is by no means meant to be a write up on the procedure for carrying out this job. We do not have the time for that sort of thing, we are busy fixing cars. It is merely an entertainment piece into the inner workings of Peak Transport and what we do day to day.
This customer has serviced there 2004 allroad with us for the last 5 years and over 50000 miles. The mileage at the time of this work was 143000 miles. Lack of maintenance would not seem to be the cause of failure in this case. The car has always had synthetic oil. The main complaint was a ticking noise at idle. Car ran fine and had no fault codes. It was obvious that the noise was coming from the rear of the engine.
Since the timing chains are about the only thing that can make this noise, the owner decided to replace the chains. This turned out to be a very good decision as two of the main chain guides where completely missing from their proper locations. Pieces of them where scattered all throughout the timing cover and oil pan.
I will let the pictures below describe the fun the ensued.
Above you can see with the front of the allroad out of the way, the engine is much more accessible. The amount of engine and cooling systems that German engineers can pack into a small space is truly amazing. We had done valve cover gaskets on this car about a year ago and the cleanliness of the top of the engine as well as the old oil residue can be seen here. Also of note, nothing is run by the ACC belt but the alternator. All other accessories are run by the timing chains. More on that in a bit.
The whole burrito in all its glory. Four timing chains, a slew of guides, tensioners, and the accessory drive in the lower left.
The close looker will see the upper guide and left side guide of the primary chain completely missing.
New chains and guides in place ready to start the reassembly journey. In the end the engine ran like new again and of course the ticking was gone. If you have a ticking noise in your chain driven 4.2L then I highly suggest you get that looked in to. And remember, we are professionals, don’t try this at home.