Brake light question

[Al Powell]

I saw your message...I assume that you're relatively unfamiliar with cars.
I'm glad to see that you have a Hayes manual and use it - that puts you
ahead of many folks!  Don't forget to check the owner's manual for your car,
as it tells you which  specific functions are covered by a specific warning
light.  I'll copy this note to the Q-list in case anyone else has
corrections or additions.

My comments are below, with * in front.

Original Message:
From: "Rafhia" <rafhia.hamilton at verizon.net>
Subject: Flashing Brake Light??

Hello everyone,
The This group was so helpful when I first brought this used car, so I am
hoping that you can help me with another problem. I have a 1988 Audi 5000
CS, that has developed a problem, that I need to fix right away. Brake light
warning came on when I turned it on this morning and I'm not too sure if
this is an indication that I need new brakes or just need more or new brake
fluid.

**If I remember correctly, the brake warning does not indicate brake wear!
That's a different light.  The brake warning indicator warns of low brake
fluid or low pressure in the hydraulic system. The low pressure light
indicates that the "bomb" or hydraulic pressure accumulator is wearing out.
It also indicates that the parking brake is on - the light is lit as long as
the handle is pulled up.  If memory serves, it also indicates low fluid
level in the hydraulic system reservoir next to the brake reservoir.  Worn
brake pads give a warning indicator kind of like this: ((O)).

I pulled out the Hayes manual so I could locate the brake fluid
reservoir and added some more fluid. From what I could see inside, it seemed
like there was fluid in there.

**But where was the fluid in relation to the fill line? There's a maximum
and minimum fill line.  "Fluid in there" is not sufficient.  You must have
it above the minimum fill line or you should see a warning.  By the way, use
only DOT 4 brake fluid in this car.

When I added more the line of fluid really didn't move.

**That cannot be, unless the reservoir was so empty that you were filling
the lines when you poured more in. If this were the case, you would have air
in your brake lines and the brake pedal would feel mushy.  I really don't
understand this statement - when you add fluid to a reservoir, the fluid
fill level MUST go up. Once again, make sure to fill the reservoir to where
the fluid is above the minimum line.  You can see this more easily by
holding a flashlight on the opposite side of the reservoir when filling
it...most of those reservoirs are so old and dirty that it's hard to see the
fluid level.

When I started the car again the "OK" light came on and
everything seemed fine. Then I turned off the car so I could put the fluid
in the trunk. I decided to turn it on one more time just to make sure that
the car was okay, but the light came on again.

**This sounds more like low hydraulic pressure than a brake fluid problem.
try running the car for 1 minute with the engine at 2000 RPM or so. Make
sure the parking brake is OFF, because that light stays on whenever the
parking brake is on. If the problem is the bomb, then after the engine has
run for a while it should build up pressure and the light will turn off.  I
suggest you also check the level of the hydraulic fluid in the large
reservoir next to the brake reservoir.  DO NOT - I say again, DO NOT put
brake fluid in the hydraulic reservoir! Your car uses only Pentosin (a
synthetic mineral fluid) for the hydraulic system.  Adding brake fluid or
power steering fluid will damage the seals.  If memory serves, your car
takes Pentosin type 7 - there are two types.  Check your owner's manual, and
there may also be a label on the reservoir stating the type of fluid it
requires.  If the level of hydraulic fluid is low, you WILL get a warning
light.  (See why it's important to know exactly the functions that light
covers?)

Could you guys give me some
indication of what the problem could be. I would like to fix this myself if
at all possible. The last 2 times we went to the mechanic (for a new
radiator, replacement of hoses and belts, pump, etc) it cost us over
$1,000. I didn't realize how hard it is to maintain an Audi on a grad
student budget.

**The more you do yourself, the better off you will be. But don't buy parts
or service from an Audi dealer!  I hope the above info helps you isolate the
problem, and that it turns out to be low fluid.  If you have to replace the
bomb, you can do so and there is plenty of info in the archives - but do it
correctly, because that system has 2200 PSI of pressure in it - that's
dangerous if you don't release the pressure before opening the system.

************************
Al Powell
Fort Collins, CO
apowell at gocougs.wsu.edu
************************