Timing Belt: 12V 2.8 (LONG procedure)

[Elliott Potter]

david kroth wrote:
> 
> Anyone ever change the timing belt in a 12v 2.8
> engine?  My '95 A6 is past-due and I'm balking at
> the $500 - $600 estimates I'm getting from the
> dealer and independents.
 
$500-$600 is relatively pretty good, actually.  However it's not so hard
to do yourself (take that, you 5-cyl guys).

> I have the Bentley, but it is little short on
> details for this procedure.  All the mechanics I've
> spoken with did recommend changing the water pump
> and idler/tension pulleys at the same time.
 
I agree with your mechanics.  And the Bentley is a little short on
details for everything...

> If there are any tricks to getting the old belt
> off and new one on I'd appreciate hearing about
> them.

Here ya go; I'm going to post the full procedure to the list for the
purpose of peer review, and if it's good it's going on my web site
(12v.org) whenever I get to it.

Tools you'll need/want:
- 5mm, 8mm, and 10mm allen wrench sockets (that go on your favorite
ratchet ... regular allen wrenches won't do)
- 6mm allen wrench
- 10"-12" socket extension
- Flexible socket extension
- 10mm 6-point deep hex socket (or shallow socket with a short
extension)
- 24mm (? I think so) 12-point socket
- Of course your ratchet to go with all of that
- A torque wrench is handy too.
- Audi tool #3242, the crankshaft holding tool.  This is VERY handy. 
You cant rent it at Blau, I think.
- Audi tool #3243 is also helpful -- the camshaft holding tool. 
Conceivably you could do without this one.
- Two large buckets
- Safety glasses
- Big flat head screwdriver
- Channel locks
- A small razor blade with a long handle...I have one that's made for
scraping window glazing that works very well.
- <insert your favorite method of lifting the car a few inches here>
- A spare mode of transportation is helpful, in case anything goes wrong
and you have an emergency trip to your local parts shop.

Parts you'll need/want:
- Timing belt (duh)
- Accessory belt (why not, you're there, right?)
- Water pump
- Coolant thermostat with o-ring
- Timing belt tensioner
- ~1 gallon of antifreeze (get phosphate free stuff that's safe for
aluminum)
- ~1 gallon of distilled water
- little rubber o-ring for the coolant drain plug on the block

Right.  You can see some of these parts in pictures at
http://eep.burdell.org/dev/12v/engine.php?section=diags

1-Remove the big black plastic cover that goes under the engine, then
remove the bracket that holds up the backside of it (two bolts to remove
the bracket).  You'll see a deeply recessed 8mm bolt at the back
(driver's side) of the engine block, that's the drain plug for the
radiator fluid.  That's why you needed the long socket extension!  It's
going to be pretty tight.  Have a *large* bucket handy; remember the
system holds 11 liters!  This is a good time to be wearing your safety
goggles, since the fluid likes to spray everywhere.  Remove the radiator
cap.  Go inside, wash your hands, and eat lunch while the fluid drains. 
You'll need the strength for later!
2-Get another bucket.  On the bottom right (as you're looking at the
front of the car) of the radiator there's a red thumb screw connected to
what looks like a little miniature faucet -- that's the other drain
valve.  Put the bucket under, unscrew, and drain some more.  If it looks
like the bumper will get in the way, you can either remove the bumper or
stick a piece of 3/8" rubber tubing on the end of the drain and stick
the other end in your bucket.
3-At the top center of the firewall, there are two 1" hoses going
through the firewall.  One of them has a bleeder screw on top.  Twist
the screw--it will break off in your hand.  That'll be $50 bucks because
the screw comes with the hose.  I was fortunate to have another plastic
screw with the same threads (I don't know where it came from or what it
was for, but it fit *perfectly*) ... works just fine.  You may be lucky
and the screw might be just fine...my car is a '93 so those extra few
years probably had something to do with it.  Anyway this is a bleeder
screw...loosen to help flush out extra fluid.
3b-Peer down behind the driver's side cylinder head, and you'll see the
coolant line that comes off the block.  It makes a 90 degree bend
towards the middle of the engine, and just after that bend there's a
sensor, and then a little screw (maybe 10mm?) with a 5mm allen wrench
head on it -- that's the other bleeder.  You'll want your long socket
extension again, and loosen this.  Only loosen it a turn or two, because
if it falls, you will never find it.
4-Remove the first layer of plastic covers on the front of the engine to
expose the accessory belt.
5-Get your 24mm socket and twist the crankshaft clockwise (as you're
standing at the front bumper) until cylinder 1 is at TDC.  At TDC you'll
notice that the oblong plates at the ends of the camshafts are pointing
towards each other, with the big hole on each closer to the center of
the engine.  Also there's a little notch scratched in the accessory
belt's main pulley that corresponds to a little arrow in the plastic
cover that's mounted directly behind it.
6-Crawl under the engine with a flashlight, a 10mm socket, the flexible
socket extension, your ratchet, channel locks, and the crankshaft
holding tool.  Look around until you see the crankshaft position sensor,
which is mounted near the middle of the engine block, up and back from
the oil pan.  It's long and flat and has a big wire sticking out one
end, and a 10mm hex bolt in the other.  Remove the hex bolt, and pull
the sensor *straight* out with the channel locks.  Screw the crankshaft
holding tool in.
7-Mark the direction that the accessory belt is mounted unless you're
replacing it -- if you put it back on, it's got to go the same
direction!
8-On the tensioner bracket for the accessory belt, there's a spot for a
10mm allen wrench -- plug your 10mm allen wrench socket in there, attach
your favorite ratchet, and twist clockwise.  This will free the belt and
you can take it off.  If you look closely, there's a little hole on the
tensioner just down from where you inserted the socket -- if you have a
handy 13-15mm bolt, you can push the tensioner all the way down and
stick the bolt in the hole and it will keep the tensioner down and out
of the way.
***note!  Step 8 is for 1992-1993 V6's and the tensioner is different
somehow for the later ones -- maybe someone can help out here?***
8b-Remove the 8 8mm bolts that hold the pulley/vibration dampener on the
front of the crankshaft.  Remember it's heavy so don't have your feet
under there.  
9-Now you need to remove the timing belt covers.  There are metal clips
on the top and bottom of each side.  Start with the one on the driver's
side.  Unclip, pull up and wiggle them around until they either come
free or break.  If they break (my left one did) make sure you get all of
the plastic bits out.  The bottom one will come off last.
10-Attach your camshaft holding tool if you have it.  The cams are
perfectly happy to stay in place as long as you don't put too much
pressure on them, but it's good to have the tool there.  If the cams do
slip, it's probably worse for your heart than the engine.
10b-Note the tension on the timing belt.  You should be able to twist it
90 degrees without too much difficulty.
11-Loosen (don't remove it just yet) the bolt that holds the timing belt
tensioner in place.  Slip the timing belt off the tensioner, then off
the crankshaft sprocket, then the other idler pulley.  Loosen the belt
around the camshaft sprockets and water pump so that it isn't stuck
anywhere.
12-Remove the camshaft holding tool, and remove the timing belt.
13-There are nine screws holding the water pump in -- remove them and
pull the pump off.  If you're lucky the gasket will also come right
off.  If not, whip out your razor (carefully now) and ***carefully***
scrape off the rest of the gasket.  ***DON'T SCRATCH THE ENGINE OR
YOU'LL BE SORRY!***  Don't let too much of it end up inside the engine.  
14-There's a big radiator hose that comes off the bottom left of the
radiator, goes up about 6 inches, and into the left side of the engine. 
That's not actually the engine, but that's what you've got to remove
next.  Take the upper part of the hose off the thing that plugs into the
engine.  Follow what it plugged into to your right, until it ends, just
to the left of where the water pump used to be.  There are two 10mm hex
bolts holding it to the block.  Remove them.
15-Now you've got to convince the thermostat to come out.  Pry it with
small screwdrivers, then big ones.  Cursing helps, as long as no small
children or spouses are around.
16-New thermostat goes in just like the old one -- there's a little vent
on the top; make sure it stays on top.  Don't forget the O-ring, which
is probably stuck to the metal duct.  Put the metal duct back on, and
re-connect the radiator hose.
17-There's a little pin sticking out of the engine that's a handy hanger
for the water pump gasket.  Stick the gasket on that, then carefully set
the water pump in place.  Make sure that the pump and the gasket are
both straight.  If the gasket isn't straight, don't try to squish it in;
remember it's paper and it will crease (and leak).  Screw the water pump
bolts in finger tight.  Then grab your torque wrench, set it at 10Nm (7
ft lbs).  If it doesn't go that low, just keep in mind that 10Nm is not
much pressure.  When you're screwing in the pump, don't tighten the
bolts in order, or the gasket will become deformed.  Do one bolt, skip
4, then skip 4 again, etc until you've hit them all -- like you tighten
lug bolts on a wheel.
18-If you got a new tensioner, now's the time to put it on.  I replaced
the other pulley at the same time, but that one wasn't in such bad
shape.
19-Loosely thread the timing belt over the camshaft sprockets and under
the water pump, then re-install the camshaft holding tool.  Now put the
teeth of the belt into the camshaft sprockets; make sure you get the
right tension.  If you were doing this the right way, you would have
loosened the camshaft sprockets to get this tension exactly right. 
We'll assume that it was already good.  If that's not a safe assumption,
one of our resident list mechanics can correct me here.  Once you've got
the proper tension around the camshaft sprockets and the water pump,
thread the belt around the idler pulley, the crankshaft sprocket, and
the tensioner (last).  Get good tension on the rest of the belt and
tighten the tensioner pulley.

The rest of the procedure is pretty self-explanatory if you've made it
this far.  Just remember these important tidbits:

- Don't forget to remove the crankshaft holding tool!  DOH!  Also don't
forget to put the sensor back in the hole when you remove the holding
tool.
- Remember, one drain on the block, one drain on the radiator, and two
bleeder screws all need to be closed for your engine to hold radiator
fluid.  It's easy to forget the bleeders...
- If you don't replace the accessory belt, remember it needs to go on in
the same direction it was in when you took it off!
- Don't get all excited and put on the accessory belt before the timing
belt covers, or the accessory belt has to come back off...

That's all that comes to mind at the moment.  Other listers care to jump
in with suggestions/comments?

--
Elliott

(*whew*)