It's good to be back (again!). Canada trip report.

[e6941tb@gnn.com]

Fellows!

I am finally back in Philly and on-line. Life in a q-list deprivation
once again proved to be difficult to cope with.

First off, maybe you remember that I was anxious to fix two major
problems with the red Q before the then forthcoming trip through winter
Canada, which was to last for more than a fortnight.

The first one was with the rear brake calipers, binding the rotors after
a few agressive stops and/or a cabin full of passengers. The pedal
itself would easily travel maybe about 40-50mm (as if air were in the
sys, which was not!) after which it would feel like a rock. The
effectiveness would drop by one-half. After 5 min of standing still
everything would get back to norm. This was so difficult to catch that I
had to drive with a 2.5 ton hydrolic jack as a passenger. One day I
drove like crazy, made the brake bind and quckly jacked up the whole
rear axle of the car. I could hardly turn BOTH rear wheels by hand, as
if the e-brake was pulled up by a coupla clicks. Naturally I started to
suspect either a proportioning valve ($$) or both rear calipers($$$),
altough leaning more towards the prop valve since 1)I have rebuilt the
calipers this past summer and 2)both calipers were binding with the
equal force (give or take a coupla kg) and I do not believe either in
miracles or coincidences. I ordered a prop valve, which turned out to be
a rare item.

Fortunately for me Jad Duncan had posted a similar problem about his '89
90 at_the_same_time, to which Al Powell, Bob Russell and Mitch Loescher
responded by saying that the Master Cylinder was sticking. It had
suddenly occured to me that the damn MC was the only original part left
in the brake sys on my '89 200. Good guess, gentlemen! Thank you very
much. It was the MC.

My gratitude also goes to Mark Show for suggesting to check the
hydrobooster for leaks at the same time. It is still OK, although it is
the only original component left in the hydro sys, that I've not
replaced/rebuilt yet.

The MC was $200 from my local parts go-getter ($470 from a dealer -
ouch!). Jim @ Blau suggested a 5000 unit for $98 which according to him
would've fit. Without questioning Jim's competence (he knows Audis
pretty well), but given a substantial price differential, I've asked
myself a question: where's the catch? Oh, well, back to my collection of
microfiches for all 44 bodied Audis. All 200 owners please take note of
the following:

A 10v 200 will take 3(!) different MC's (and 2 different hydroboosters):

1. VIN up to 44_K_010 000: 447 611 021 (25,40x18/18)
2. VIN up from 44_K_010 001 on: 441 611 021A (25,40x17.5/18)
2a. also use: 853 612 129

A 5000 will take 2 different MC's:

3. 443 611 021 (23,81x19/17)
4. 447 611 021 (25,40x18/18) for vehicles w/larger permissible load (and
wagons).

Please note that §1=§4. Which means that a 5000 unit would probably fit,
but hey, we have a 200 with a larger (25mm vs. 23mm dia.) bore in the MC
for the improved braking ability. To me it was definetly worth extra
$100 and I ordered the original one.

After I installed the new MC (naturally after bench bleeding it first)
and replaced the brake fluid with 2L of fresh DOT4 Pentosin, I couldn't
resist the temptation to take the old MC apart.

Audis would be the only cars I owned, on which I haven't ever rebuilt a
MC. Audi's MC is not rebuildable and the repair kit does not exist for
them. That's a damn shame! The last MC, that I've rebuilt, was from a
320i, that I had briefly owned, workes well up to this day. (Somehow I
never got to like a Bummer, but that's another story).

Well, fellows, it took me a lot of drilling, filing and chiseling to
open up the sucker. I addition to a regular locking C-clip in the groove
SOB had a 2cm cavity ander it filled with....EPOXY! The cylinder is
sealed permanently, I haven't ever seen an MC built like this.

Secondly, unlike the Bummer and the rest, our MC has 2(!) shafts with
the sequential action. During the first half of its travel the pedal
operates the rear shaft (and its piston), which sends the pressure to
the rear wheels. Then the rear shaft hits the front one and the later
starts to move (with its pistons), activating the front brakes.

NOW everything has become clear to me! During a spirited driving with hp
in the neighbourhood of 300 but on the crappy OEM (or Metalmasters) pads
the fluid starts boiling, warming up its whole volume, eventualy
convecting into the MC reservoir and causing the rear shaft of MC to
stick in the IN position. That, in turn, caused the pedal to travel
rather freely for about one-half the distance, coz I was pushing air
behind the rear shaft/piston.

After a short cool down the MC rear shaft would shrink a coupla microns
radially and release itself from the trap.

Eric, Scott, I recall our August conversation about my brake fade during
the Watkins Glen event and now I completely agree with you: It happend
because the street MMasters couldn't take the heat and caused all of the
problems with fluid boil and MC sticking (even though I've been using 
ATE Racing Blue and DOT4 Pentosin german brake fluids).

The second problem was with the Control Pressure Regulator. The car
required a foot on the pedal for the first 5 min after starting it at
subzero temperatures (°C). I suspected a faulty reg (or a bimetal
strip).

I want to thank Geff Goggin for faxing me a gazillion-page WMB pamphlet
on udjusting the CPR, Dave Head for offering me his fuel pressure tester
(I have my own) and Phil Payne for the advice on testing procedures.

The CPR passed all of the tests with flying colours. "Puzzling", sez I
plugging everything back in (including the electrical connector). Let's
see how it behaves in subzero climat of Quebec.

The red Q performed flawlessly, exhibited excellent manners abroad (I
was not ashamed of it) and in the morning would start from a 1/4 turn of
the crank down to -17°C, that we've seen in Canada. My guess is since
the electrical plug was last touched in Ingolstadt in May of 1988
(according to the build date), its contacts have plated themselves with
a layer of Ag2O3 thick enought to disrupt the continuity. Being an E.E.
I should've thought of it before hand! Just unplugging the connector and
plugging it back in must have scraped the contacts and reinstated
continuity. A text book case, shame on me!

To all of the fellow Canadians on the list: you live in a beautiful
country and are a wonderful folk. Thank you for your hospitality! We had
a great time.

I have the impression that Montreal (and especially the old Quebec City)
are about the only places in North America, that carry a distinctive
european charm.

Igor Kessel