Why do i need to change cam belt and tensioner at the same time? is it a must

You buy a complete kit

That includes the water pump,timing belt,all
idler pulley's ,so you don't have to go back
there when the water pump fails

Just like you replace brake hardware, sometimes,
as it rusts,wears & heat cycles

You do your belt at 140,000 km (84,000 miles) about
every 7 years (12,000 per year)

I think that if belt is wore out that the tensioner wont be to far behind it or the reverse if you change tensioner the belt cant be far behind , and its not something you want to go back in and do over in a few thousand miles .I hope this was helpful.
Woody

A tensioner will generally outlast only one timing belt, Longa, and it's a lot cheaper (for YOU) to change both at the same time than it is to open the engine twice - once for the belt, and again later for the tensioner.

The timing must be off. There is a crank lock that must be installed when changing the belt and also a holding "jig" that holds the cams in place while you are changing the belts. Also the cam pulleys must be separated and free from the cam shafts when installing the belt and tensioning in order for the engine to be timed correctly.

Belt tensioner puley.Sience you said timing belt was done , that means water pump was replaced too.
Just had same thing in the shop , weard noise hard to tell were from , happened to be a serpentine belt tensioner puley.Can't replace puley only , it comes as assembly.

Did you try www.autozone.com? Might help

ring your local audi parts dealer with your reg plate

I need to find a diagram to show the placement a serpentine belt, for an 1999 adui a4 2.8. I also nee to know if ther are any trics on how to get it on.

thanks

CHANGE THE BELT AND TENSIONER. These are interference motors and absolutely have a required service interval for the belt and tensioner (and a mix of other pieces as well). Gchevere001, please do yourself a favor and don't listen to the friend you mentioned. If you follow his advice you will be paying for a new motor down the road.

Audi calls for the full timing belt job roughly every 60k miles. If you're not sure (as in, you haven't seen receipts showing) when the job was done last, spend the money and do the job now. You don't want to pay to replace one of these engines.

There are various kits that you can buy, including varying numbers of pieces, and no one mentioned which engine they have, but the basics of what you need to do are the following: Change the timing belt, timing belt tensioner, serpentine belt, serpentine tensioner, timing idler roller, relay level for the t-belt, water pump, water pump gasket, G12 (pink) coolant, and thermostat. Often cam seals and front main seal are done now as well, and if yours are leaking oil or look damaged, then do them too (if they are sealing fine and look good, don't mess with them and risk creating a problem). You're going to want to invest in at least a Haynes manual to walk you through it, plus supply the torque specs for the various parts you're installing. Also, on www.audidiy.com and www.audiworld.com there are step-by-step procedures for doing the job on some of the A4 engines, so take advantage of those as well. But yes, you do have to change the timing system - at least the parts I mentioned, not just the belt.

The 1.8T is very common in the US. We don't have any diesels here in the A4, but the 1.8T is all over the place.

What exactly do you need to know? You were posting it in the title to your question but it got cut off and I don't know exactly what you're looking for in terms of info for changing the cam chain. If you mean the timing belt, that's a belt, not a chain. I thought that the 1.8T drove both cams off of the belt, unlike the 2.8, where only the exhaust cams are belt-driven by the timing belt, and the intake cams drive off their respective exhaust cams via a chain and tensioner assembly. If you can clarify this, we can proceed.