I have an issue which I need help diagnosing and fixing. I may leave it to a pro but looking through the Bentley manual it looks really easy to replace the master cylinder.

So I flushed and bled my brakes because my braking was not great and pedal travel excessive. After I was done the pedal is better after driving a bit but not like I thought it should be. It requires some travel before it begins to brake. When it does engage the brakes are solid. Immediately after bleeding the pedal was really low and sucked, but much better after driving a bit. Another point, I have been monitoring my brake fluid and its been the same for a couple weeks now after the flush. So I don't have a leak.

After looking through the Bentley manual under problems it says that a low pedal after bleeding is a faulty master cylinder. How can I be sure? My brakes work pretty well, I just don't like the lower pedal and don't want to autocross that way.

Second, what about the vacuum booster? After my car has been shut off and sits for a while the pedal is rock solid and I have read on here that is possibly due to a leak in the booster.

Any help appreciated,
k

Oh, and is replacing the master cylinder as easy as the bentley manual shows? I have heard of having to bench bleed a master cylinder before installing. I have no idea what that is. Do you just bleed a new master cylinder like you would if you were flushing the system?

 

Sounds like a faulty master cylinder to me. It's not the brake booster, the pedal will be rock solid all the time if it were.

They are very easy to replace, you just need to remove the air box and the right partition and that's it. As for bleeding, if you have a pressure bleeder handy, that will do the trick just fine, you won't need to bench bleed it. And bleed it as you were flushing the brakes, making sure the bubbles stop coming out before you close the bleeder.

 

Thanks for the response. If I don't have a power bleeder can I just bleed a dry master cylinder the old fashion two man way? I have also read that the master cylinder and brake booster are recommended to be replaced together, is that true and why?

Also, I am pretty sure I have some sort of vacuum leak. After I shut the car off 5 minutes later the pedal is rock solid and no vacuum present. The vacuum should be able to remain over night right? I am going to get a mity-vac hand pump and check the booster to see if possibly the check valve is faulty.

Can the mity-vac pump be used to power bleed as well if I end up replacing the master cylinder?

Lastly, is there a good source for quality rebuilt master cylinders? My dealer sells it for $280 through my local mini club discount. Classic sells it for a little less but I would have to pay shipping.

 

I went out today to some empty parking lots and back roads and really heated the brakes up. I am assuming my pedal travel is with in normal limits and I am just expecting too much pedal feel. Stopping was great after many repeated full on 50 - 10 and 60 - 10 stops. I just have to track down the little vacuum leak...