My S6 (V8 4.2L C4 platfrom) is due for a timing belt change. Water pump and engine is very quiet when running. I want to simply fit a new belt for now, and re-use the old tensioner and idler pulley, if they look good.

I planned on lining up all the timing marks before removing the old belt. So will I really need a camshaft holding tool?

Well, how shoud I say it... If this is Your first timing belt change, or You aren't familiar with (what is this 0.01mm timing clock) clocks, it's easier to use locking tools.

My experiense of Audis V8 engines are, they wery sensitive of timing. Even You use locking tools, maybe engine doesn't run smootly or it will use extra gas. This can come because with locking tools there is 5mm tolerance in crank shaft. And syncronising cam shafts with crank shaft exatly, You will have to use timing clocks. Then Your engine run smootly and it will use 10l/100km in mixed drive. In towns it use less than 11.4 l/100km.

So, when You have used locking tools, and You start Your engine. If it doesn't run smootly, re-install everything again... and again... and again. So many times Your engine run smootly from beginning.

Locking tools cost ~120€ wit taxes in Finland, and we are expensive coutry. But if You compare it to price 1800€ they charge changing timing belt, it pays off. Is there any friend You can borrow theese locking tools?

And my addvice to bearings and rolls... Change them all !!!
Nothing isn't moore frustrated than braking Your engine because of 23€ bearing. When I bought my car from Germany, I noticed somebody hasn't change bearings. They kept bad noice. All bearings, belts, spark plugs, air filters and gas filter cost totally 430€. Of course it's a lot of money. But You car drive next kilometers without problems.

/pete

I'm not agreeing with Pete. When You will keep distances (in belt's teeth) between characteristic points of every gear pulley, there's no possibility to change timing. Notice, that after tensioning a belt, there's no posiibility to change timing (telling differently: change position of crank, and each camshaft) by less, that ONE TOOTH distance. So any "milimetric" errors in timing are not possible at all.

But I agree in 100% with second part of Pete's post: Saving some pences on new bearings and tensioner isn't worth a grief, when You must pay for another engine in place of Yours - internally damaged due to timing crash...

So - JohnW - buy complete set for Your machine, and after that - take a great care with changing timing set yourself. In audi V8's it's really complicated. Turn attention, that You can tension the belt with two bearing: tensioner, and excentrical mounted roll bearing. Study properly, how tensioner works, and guess propelrly what for addidtional tensioner exists!

look here: http://www.audipages.com/Tech_Articles/enginemechanical/tbreplace0.html

it might be some help for you.

Johan.... that's more than 2 years ago...

i´m sorry,i didn´t look at the date in the post