[s-cars] Timing Belt and Headgasket replacement update, observations and lessons learned - long

[Ingo Rautenberg]

As you may recall, some weeks ago I sought to replace the headgasket and
timing belt and water pump on my 200q20v.  I finally finished the job,
though I definitely recommend against trying to do a job like this quickly,
because you never know what things will pop up.  A big 'Thank You' to Kneale
for use of the timing belt tools -- I really can't see doing the timing belt
in confidence without them -- plus you'll
need a 3/4" 255 ft. lb torque wrench.  Also, as I was going to replace the
suspect headgasket (three ballooned leaky expansion tanks and a replaced
pressure cap despite lead to suspected incomplete headgasket seal), I
enlisted the help of a friend to remove and reinstall the cylinder head with
intake manifold/exhaust manifold & turbo as one.

The removal of the turbo down pipe is highly recommended -- otherwise turbo
to downpipe studs will need to be extracted -- not too difficult when unit
is removed, but damn near impossible when trying to install in the car-- I
did it, though.

I didn't expect to see anything obvious with the old cylinder head gasket,
as the compression check was well within spec before(150-150-145-150-150),
and didn't see any obvious failure.  The original headgasket was of the
composite metal-fibre type, with the obvious metal-reinforced cylinder bore
rings.  The replacement is an all-metal multi-layered composite that would
appear to afford much higher sealing properties (we shall see).  I inspected
the head and valves for problems/variances between cylinders and could not
find any cracks.  The pistons and combustion chambers had minor carbon
build-up and cylinder walls revealed cross-hatch honing marks after 162k
miles (gotta love the bottom ends of these motors).

I thought I'd simplify things when I removed the cylinder head with
manifolds and turbo attached and disconnected the turbo oil feed line at the
block (actually the oil filter bracket) instead of at the turbo.  Bad idea!
Reconnecting this is a bear, as there is a certain amount of tension on the
fitting and the threads nearest the block in my case were stripped!  I
happened to have a replacement in case I needed it (for my Urquattro
upgrade), but would have also needed the oil filter bracket to engine block
gasket, which I would have had to order.  Solution:  Use 1/4" Allen bolt
instead of 6mm -- it works!  Also use new gasket ;-)

I replaced the water pump as a preventive measure (one on there was original
with VW/Audi OEM castings) and the idler pulley, which was definitely on its
way out (noisy bearings) and recommend that it be done as a matter of
course while doing the timing belt. I also made sure not to have the timing
belt too tight, being sure to turn the motor a few revolutions with the
crank bolt  a few times to recheck (remember -- counter-clockwise).

Replaced turbo side motor mount (which was totally separated and useless).
Still need to do passenger side one.

I reattached all the electrical connections, vacuum hoses, replaced the
distributor cap and the turbo bypass valve and started her up with  no
problems... yippee!  Or so I thought.  During a midnight test run I popped
the lower turbo to IC hose at the turbo three times (apparently used the
wrong clamp) and under minimal boost (<10lbs).  With that solved, I ran into
my second-scariest problem (after the stripped oil filter adapter mount):
Rough running (four cylinders).  I pulled each plug wire staring with No.1
and ending with no. 5 (culprit).  So now I new that something was wrong with
no. 5, but was it Spark or fuel or GASP! headgasket failure?  Compression
check was exactly as before (150-150-145-150-150), so headgasket failure was
unlikely.  I removed the plug wire and checked continuity ~6.4 k ohms
(within spec).  So then I swapped injectors and retested.  No difference.
Swapped spark plugs. No difference. What was I missing?  Swapped plug
wires -- aha!  Inspected suspect plug wire again and found cracked rubber
insulation where the connector connects to the top of the spark plug, which
is a big problem in our cars, because the spark will go to the path of least
resistance (in this case the surrounding spark plug cavity from the top of
the valve cover to the spark plug threads in the cylinder head.  Temporary
fix is 600v rubberized electrical tape wrapped around the rubber spark plug
connector.  So far so good (but a new plug wire set on the way).

Unfortunately, I had replaced the seriously-dirty leaky expansion tank with
a new one and was now getting it really dirty, with apparently some of the
oil mixing in with the coolant during the  headgasket replacement procedure.
I was reminded that back in my dealership days we had similar problems with
944 turbo oil/water heat exchangers that had sealing problems.  P*rsche
recommended pouring half? a bottle of SHOUT laundry detergent into the
cooling system, running the engine for 20-30 minutes and subsequently
flushing the coolant system.  I did this a few times because some time ago I
had used one
of those copper-particulate radiator stop leaks and wanted to flush as much
of this stuff and other particulate matter out of the system as possible.
In addition, the pervious owner had switched the coolant to the newer Audi
Red stuff (similar to Dexcool?), and I wanted to have coolant that I could
obtain readily in emergencies -- plus I still believe in replacing coolant
every few years.

Will post update later, but so far so good.  I had ordered additional crank
seal, but did not use as old one was not leaking -- hey, if it ain't broke
don't fix it, right Bernie?

Conclusions (in no particular order):

1.  Have patience.

2.  It helps to have someone assist (though not necessary for timing belt/
water pump and related-only job).

3.  Problems often have simple solutions (i.e. plug wire).

4.  Replacing motor mount significantly reduced trans noise when
decel/coasting in 3rd and 5th gears (trans mount had been replace 1 1/2
years before).

5.  Moaning from the engine on light boost (1-3 psi) was eliminated with new
bypass valve (ending in 108) which replaced 102.

6.  Spare vehicle is a good idea :-)

-Ingo
'91 200q20v...Slightly modified and back on the road
'83 Urquattro
('90 v8q RIP)
http://hometown.aol.com/quattringo/index.html