[s-cars] A4 head rebuild, Part 1

[Igor Kessel]

Hello, folks. Here's another one of my long and nerdy posts.

As you might remember, over a month ago my wife's car ('98 A4 1.8T
quattro) had spun the timing belt, with the expected disastrous results.
Below are a few notes should anyone contemplate doing the head rebuild
himself. I am CC:ing the S-list and the Q-list coz I've made a few
important observations that might be useful as a general knowledge.

PART 1 - disassembly.

1. Disconnect the battery! You don't want to accidentally spin the
engine with the timing belt off. I have a horror story or two to tell,
but I am bound by my word given to the hapless car owners/their
mechanics so I'll keep quiet on this. But take my word for it, an
accident like this WILL ruin your day.

2. The A4 is almost as technologically user friendly as its 5 cylinder
predecessors which we all know and love. As always prior to doing
anything even half serious with the engine you really want to remove
those two bolts that hold the bumper and take it completely off the car
instead of trying to be a contortionist by reaching your left ear with
your right heel.
The rest of the front end takes some careful disassembly but it is
designed rather elegantly. The radiator now has a drain valve
(hallelujah! Hans und Klaus have finally figured out that draining the
sys through the lower radiator hose is a low tech approach even by the
GM standards). Naturally I drained the antifreeze completely coz at 4
years of age it needed replacement anyhow. Plus the water pump and the
thermostat were to be replaced alongside the timing belt which is a
general rule for our cars.
The face comes out and off to both sides of the car like an open book.
The whole huge plastic radiator support with the headlights goes to the
left as an assy. The A/C condenser - to the right and gets strapped to
the RF wheel. You really don't want to step on that part accidentally.
Almost nothing gets disconnected. Freon stays in the sys. Did I mention
how service friendly the Audis were? :)
For those less comfortable with the disassembly there is an excellent
pictorial write-up on Audiworld named "Timing Belt and Tensioner FAQ" by
Andy TN.

3. The head removal is trivial, only much easier than on the 5 cylinder
Audi. Even the small stuff, like the injectors come off as a single
manifold. The hoses are on quick disconnect clamps. The turbo now stays
on the downpipe, along with the integrated wastegate. No more cursing
and bitching while removing that huge and heavy 5 cylinder head with the
cast iron exhaust manifold and the turbo attached to it! And so forth.
Nothing really to write about. Just follow your Bentley.
For the head removal you will need at least one special tool: the long
10mm 12-point Audi tool a.k.a. the "triple square". Zelenda's number
3410. You will need at least two other special Audi tools which I will
mention as we go along.

4. At 9.5:1 the 1.8T is an interference engine. This means that should
the timing belt break (or seize up due to a defective tensioner like in
many many other cars of the same vintage as mine) the pistons WILL meet
the valves. For some mysterious reason each 1.8T piston has only one(!)
flycut for the slightly offset inner intake valve (which otherwise
would've been in the imminent danger of meeting the piston). The other
two intake valves are not at risk due to the design of the combustion
chamber and their angle. Hard to explain but this becomes evident once
you look at the head from the inside.
Both exhaust valves are of a slightly larger DIA than the three intake
valves and they do interfere with the piston. But for the reason unknown
Audi has decided not to place the corresponding flycuts in the dished
piston crown. Thus if the belt breaks, within only one crankshaft
revolution all exhaust valves will start to resemble nails that I have
pulled out of my porch with a nail puller. And, as we all know, the Audi
exhaust valves are hollow, filled with Na and thus cost a fortune to
replace (the dealer price was $89/ea; I paid $42/ea, thank heavens
there's Rod and TPC).

(to be continued)

--
Igor Kessel
two turbo quattros