Brake problems on Ur q?

[gregory@innotts.co.uk (Ian Gregory)]

Hi All

Having got as far as I can go on sorting out my suspension whilst waiting
for parts, I have moved on to the brakes.  Whilst understanding the Brake
Fluid side of the Brake systems OK I am uncertian of the Hydraulic Power
Assist side.

When I got the car (it is an '84 UK Spec) I knew the brakes would need
looking at, they are innefective esspecially at speed.  The pedal was firm
and would travel 1/4 to 1/2 its length initially, but if pressed hard as in
an emergency stop, it would sink another 1/4 travel suddenly and then
become hard again.  The brakes are VERY front biased, the back brakes do
not seem to be used hardly at all.  They are not seized and move freely,
but the bias seems very wrong, coupled with the apparent lack of power
assist you can imagine the feeling when a deer crosses suddenly in front of
you and you are on boost in 4th?

As an interim measure I had the Fluid flushed by a garage last week, this
made no difference.  So last night I replaced the Master Cylinder and bled
the Brake fluid system fully (including the Master cylinder and Bulkhead
Bias valve) and replaced with new Dot 4 fluid.  This has made no
difference.

When pressing the brake pedal hard a short hiss comes from the area of the
"Bomb", it seems to come from the unit at the bottom with all the pipes on
it (Regulator?).  This has sensors attached to the right side and bottom as
well as various pipes from and to the Pump, Resovoire and Steering Rack.
When driving the Brake system warning light comes on after a period and the
"Voice" warns of a major brake malfunction.  If the brakes are used hard
then the light goes off for a while but comes back on after a period of no
braking or idling.  The ABS is out as well (Might not be related).

The power steering seems OK but occasionaly is stiff at very low engine
speeds (like when parking sometimes but not often).  The fluid resovoire is
full to the brim.  There are no noises from the pump that I can make out,
the belts are tight and OK.  There are no visable leeks anywhere on the
Hydraulic system, and it isn't losing fluid from the resovoire.

How can I test the various components?  What are the most likly ones to
have failed?  What order should I replace things in (Bombs and pumps are
expensive), or can some things be cleaned out and or serviced?  How do I
bleed the system?  I have bled the power steering by lifting the wheels and
lock to lock with no engine, then lowered and the same with engine running.
This made no difference to the fluid level.

Sorry about the very long post and all the questions, but I have tried to
include all the pertinent info, to help in finding the problem.  Any help
would be very much appreciated.  :-)

TIA

Ian Gregory                                       MicroStar Communications Ltd
Technical Director                                          P.O.Box 233
                                                             Nottingham
'88 90q                                                       England
'84 Urq                                                        NG8 6HD

 Tel : (115) 913 5130 - Fax : (115) 913 5129 - Email : gregory@innotts.co.uk

              a quattro is for Life, not just for Christmas!