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Re: Audi brake fluid
>I think I goofed up big time with the brake fluid type on my audi 90 (1988).
I think you're okay there. See below...
>Couple of weeks ago, I posted that the grommets under the brake fluid
>reservoir is leaking and seeked advise. I managed to replace
>the grommets and the leak stopped. However since then I have noticed that
>the feel of the brake pedal had changed. Today I noticed that with light
>pressure on the brake pedal, it sinks to the floor indicating a bad master
Perhaps there's still air in the brake lines. You should bleed the brakes
>The brake fluid that I used was the generic DOT 4 type. The owner manual
>says that the brake fluid and the power steering fluid are the same type
>and I remember that there was discussion a while back regarding power
>steering fluid and how important it is to buy it from Audi. This combined with
>the fact that my master cylinder has gone bad is making me suspect that the
>brake fluid is incompatible with the rubber inside the system.
No. The brake fluid that goes in the reservoir above the master cylinder
should be DOT-4, as you have correctly used. There is a separate cylindrical
reservoir for the power steering (and power brake servo on some models)
that requires hydraulic fluid. Some Audi models specify Dexron II ATF,
while most others requires a special mineral oil from Audi. If I remember
correctly, the Audi 90 uses a vacuum brake booster (rather than hydraulic),
then the hydraulic pump is used only for the steering.
>1- Do you guys agree with my diagnoses.
>2- Why Audi is not more specific regarding this in their manual or on the
> warning on top of the reservoir. They specify DOT 4 that
> meets SAE J1703.... which is what I have put in.
You did the right thing. On Audis that require special fluid, the
reservoir does have a label stating so.
BTW, I recommend Castrol LMA brake fluid. LMA stands for low moisture
absorption, which means that it minimizes the chance of brake system
>4- Audi is quoting $290 for the master cylinder and they do not carry rebuild
> kit. Are there cheaper sources. Also are there rebuild kits for the
> master cylinder. The brake system is Girling.
>From the sound of it I don't think you have damaged your master cylinder.
Try a real good bleed job.
/// Ti Kan vorsprung durch technik
/// AMB Research Laboratories, Sunnyvale, CA. USA