[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

Re: type 44 brake question - long answer

At 09:48 AM 10/13/1998 +0200, you wrote:
>Hi Mike,
>Just read your reply e-mail to Steve regarding brakes and bombs and
>I have a question of my own regarding master cylinders and other
>brake parts. My brakes are totally useless, they were spongy when
>I got them back from a service last year, the discs are warped and
>thin, the pads are finished, the bomb is suspect (but might be
>related to air in the lines, I'm going to attempt a remanufacture
>sometime, can't afford a new one for this car), basically it is
>getting dangerous, but I can't pull money together for taking it
>to a workshop rioght now. So, about the master cylinder, you said
>something like $50 for a new one from NAPA or Pep boys or other
>places like that (Midas?). I'm in South Africa, so things might be
>a little different, but I'll probably be able to get the same thing
>from local aftermarket joints. Anyway, I have a 1990 200 auto
>front-wheel drive, turbo motored Audi, is it just as easy to get a
>master cylinder for these as it is for the early 5k? I'm thinking of
>a gearbox change/conversion so I might as well go find a master
>cylinder for the manual car, so do you perhaps know if is easy to find
>a master for the 1988-1991 Audi 100/200 manual or are the cylinders
>vastly different between the MC-engined car and the other N/A cars?
>Sorry for wasting your time if I have. Thanks in advance for any
>help. :)

>name   : gerard van vught
>e-mail : gerard@poboxes.com  / han.solo@galaxycorp.com
>         gerard@mosaic.co.za (work)


No, you are not wasting my time. <G>

The master cylinder on your car should be about the same as on the earlier
5K cars. Remember that Audi is in the habit of changing part numbers on the
slightest provocation - like different color paint on something we can't
see anyway, or different supplier for same part - so you MAY find that
while Audi lists 350 different master cylinders for the type 44 car, there
are really only two or three needed to cover the entire line.

The discount-Auto-Pep-Boys-NAPA-Autozone stores all have pretty much the
same stuff, and there are also specialist "Foreign Car Parts" stores who
also have this kind of stuff. If the master cylinder costs $50 US
aftermarket, we can expect it to cost between $250 and $400 at the Audi
dealer . . .

Essentially, you can quite probably go ahead and use the same master
cylinder for automatic and manual transmission cars - no changes needed. If
the supplier's cross reference lists it as fitting, you'll be OK.

Spongy, soft brakes: Test one: pump the brakes - if the pedal comes up and
you can get one or two good applications THEN it sinks down, you have air
in the brake lines. Getting the air out of the rear calipers is a pain - it
gets trapped in the area of the pressure regulator (in front of left rear
wheel) and also in the rear calipers themselves. Just keep at it - pressure
bleeding works better, but you CAN do this the old way.

If you never can get the brake pedal to be firm, the master cylinder is bad.

Don't try to rebuild the master cylinder even if you can buy the kit. This
is a false economy. Over the past 35 years, I have rebuilt hundreds of
brake calipers, wheel cylinders, master cylinders, clutch master and slave
cylinders, brake boosters, and even once did a brake job on a DC-7C
freighter - 132 pads per side, times two!

I was totally successful in ALL of these, but have had NO success in
rebuilding Audi hydraulic components except calipers. Even the clutch slave
cylinder wouldn't work for me, and it has only ONE miserable seal! I
honestly don't know why - it doesn't make any sense to me, and I do know
what I'm doing.

Bomb diagnosis: Steering effort is not affected by the condition of the
bomb. Heavy steering effort means bad pump (easy, inexpensive rebuild) or
rack (replace, period. $160 from Jorgen). Dead bomb will give you high
pedal effort, and after one or two quick stops, the pedal will feel very
"hard" and will pulsate - and the car will feel like it isn't slowing down!
Yeehaaa! That WILL get your attention.

Thin brake disks won't affect pedal feel - if they are warped, you will
feel it in the steering wheel (fronts, and only on brake application) or in
a pulsating of the brake pedal - this feels very different from the "hard"
pedal pulsating of a dead bomb - the speed of the pulsing slows down as the
car slows down, while dead bomb pedal pulsating is much less dependent on
the speed of the car - it also feels hard-soft-hard-soft, but it almost
feels like the pedal is "kicking back" at you. Warped brake disc pulsation
is much gentler, and the pedal effort doesn't change, just the pedal height
fluctuates up-down-up-down, but you don't feel the much harsher and sharper
"kick back" of the dead bomb.

And I am sure you don't want to hear this, but you COULD have both problems
at once . . .

What I'd do with this car is as follows:

1. Bleed brakes, carefully, thoroughly. Test, note any or lack of improvement.

Cost: two cans of brake fluid, some time, you need a helper. 

2. Replace pads, check all calipers for leaks and torn seal boots, and rear
calipers for stuck parking brake levers (common problem - remedy is
lubrication and work it back and forth repeatedly). Calipers are easy to
rebuild - fronts are almost trivial, rears are a little tricky - reading
the rebuild instructions that come with the kits really does help. Bleed
brakes again if system was opened. remeber to grease the slide pins for the
calipers. (While you're there, check your CV joint boots.)

Cost: About $100 for aftermarket pads, rebuild kits - this assumes nothing
is BROKEN when you inspect it. Saturday job.

Think about new discs - replace if obviously deeply scored. You can
probably get yours turned ONE MORE TIME, but they will be too thin and will
warp easily.

Cost: $5 to $10 each for turning your discs, $40 to $50 each for
aftermarket replacements.

Total brake job cost so far, about $200 - $300.

3. Inspect proportioning valve (inboard of left rear wheel). There's a
triangular shaped lever with a pivot on one end and a big spring on the
other. Under the lever are two metal pins with little rubber boots - these
are the actuating valves. Make sure the pins can move inward toward the
valve body - these MAY be frozen. I have a spare proportioning valve
(replaced with a good one from my parts car), and I absolutely cannot get
into it - tried EVERY trick I know (heat, bigger hammer, voodoo, cuss
words, dynamite, and more I won't reveal), and the valve bodies just
wouldn't budge out of the aluminum block.

Don't even think about buying this new - this is a junkyard part - test it
before you buy it!

Takes half an hour to change, wear eye protection to keep falling crap out
of your eyes as you lie on your back under the car.

4. Do the master cylinder tests above, and replace if needed. Bleed brakes
yet again.

$50 or so, as above.

Maybe an hour, plus bleed the brakes time.

5. Last, replace the bomb. You might try the schrader valve rechargeable
bomb trick - even though it can and has been done, I have not heard
anything on how well it works or how long it lasts. I paid $220 for a bomb,
on sale.

Safety issues completely aside, when these brakes are working properly,
they are GOOD!!! I'm afraid some airhead in a junk mini-pickup will
tail-end me - My car stops RIGHT NOW - and I know the brakes in whatever is
behind me are nowhere near as good, even assuming the driver is at least
semi-conscious and smart enough to realize that when his entire windshield
lights up bright red it means STOP, A**HOLE! . . . 

(I have a pair of serviceable rear brake disks which should fit your car
and a used, inexpensive but not guaranteed bomb which will fit - end of
advert - private e-mail to me if we can figure a way to get them there

I know you are in South Africa, so these quoted prices are only a guide for
you. It might pay you to figure out some way to open a conduit for Audi
parts from the US - through your job, school, someone you know who is in
import-export, or go into it yourself out of simple self-defense . . .

Hope this helps.

Best Regards,

Mike Arman