Hey guys,

I'm going to do the valve cover gaskets and cam chain tensioner seals job next weekend, and I plan on using this DIY: http://www.audiworld.com/tech/eng107.shtml

I have a few questions:

1. The DIY is for the 2.7L bi-turbo, but my 2.8L NA engine is similar enough where it should be mostly the same, correct?

2. Do I need to have the engine in TDC before starting this procedure?

3. Does the use of VAG special tool 3366 to release the tension on the cam chain affect the timing?

4. He mentions a 12 point 24mm bolt on the crankshft pulley he used to manually turn the engine because he was concerned that the tension on the chain didn't return after he removed the VAG 3366 tool. In your opinion, was that step necessary if the same thing happens to me? Will a regular 24mm socket work on the 12 pit crankshaft bolt, or is there another tool that will work?

The only thing that worries me about this job is the timing. I don't want to screw up the timing and end up with bent valves, etc.

While I understand what TDC means in theory, something I read confused me because it was talking about TDC on a compression stroke, or something like that.

Is there one and only one TDC, or is there TDC for different strokes?

If someone could help me understand how timing works on the 2.8L, I would be forever grateful.

 

Just a bump hoping that someone will respond.

 

I suspect I will be doing my valve cover gaskets in the semi-near future as well and have been trying to wrap my head around the process with many of the same questions that you have:

1. Yes. Once you get the covers off everything should look exactly the same.

2. If you are not doing the cam seals you do not need to be at TDC because nothing should be moving/have potential to move.

3. Releasing tension on the chain should NOT affect the timing, as long as the chain maintains the proper number of links between the cam sprockets and nothing else moves.

4. IIRC when I did my timing belt a standard 24 mm socket was sufficient to turn the crank (honestly I don't remember if it was a 12pt socket or not).

There is pretty much only one TDC. One turn on the crank gives 1/2 rotation on the cams so you can set the crank to the TDC mark and have the cams 180 degress off (make sense?)


The above represents my limited understanding. Please don't rely 100% on any of it as fact. Hopefully someone that knows can give US some confirmation or definitive answers.

 

When talking about TDC piston positioning, it occurs twice in any full engine cycle. Four stroke engines in cars (intake, compression, power, and exhaust strokes) have a piston reach TDC twice (compression and exhaust strokes) and BDC twice (intake and power strokes).

Check out www.howstuffworks.com for a breakdown, or if it's still online anywhere, years ago Sport Compact Car magazine did a 14-installment engine breakdown that covered the range, from "this is an engine" at the beginning, to variable cam timing, timing retard under boost, nitrous operational chemistry, etc at the end. The series was called "Suck, Squish, Bang, Blow" for the four strokes of the engine. If you can find it, read it - it's superbly written and phenomenally instructive.

 

Thanks guys!

Jeremy, can you confirm that I don't need to worry about TDC unless the chain moves, like Beau indicated? Just want to make sure of this before I start.

Maybe I should paint the chain at the two arrows on the cams so that if anything moves I can make sure there are still 16 links between the two?

 

You don't need to worry about TDC at all when doing Cam Tensioner Seals.

When you insert the special tool to compress the tensioner the position of the valves may provide to have too much tension, thats why you need the 12pt 24mm socket to slowly rotate the crank so that tension get loose and the chain starts to flop. When the chain has slack you can move the tensioner up and down allowing you to slide out the two piece seal. Your not removing the chain or the timing belt..... So no timing concerns need to addressed.

 

Thanks Audi Tek, that's exactly what I was hoping to hear.

I've read that some guys with manual transmissions use the "rocking the car in 6th gear" method to get slack in the chain. Is this method possible with a tiptronic?

Btw, I took Jeremy's advice and I've started to read a bit on four stroke engines and how they work. Fascinating!

 

how did this end up going?

i just changed valve cover gaskets in my 2.8 and its smoking like crazy behind there..

 

It went fine, but like you, the first time I tightened everything down, I still had a leak out of one of the valve covers. Had to take it off, clean it up and then tighten it down again. Good as new!