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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Mechanical Maintenance: Break-in / Oil & Fluids / Servicing / Warranty > bleeding brakes



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      07-23-2013, 06:31 PM   #1
tennis_pr0
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bleeding brakes

So I just have a few quick questions about bleeding the brakes. I know before you start, you should suck out the old fluid from the reservoir and put new fluid in. Now they say to never let the reservoir become empty, so how come they say to such out all the old fluid and put new fluid in?

Next, once the tube is connected to the bleeder screw and bottle with fluid in it, do I have to have an assistant for this? They say you have to have an assistant so you can yell "up" and "down" to so they can much and release the brake pedal in accordance to the opening and closing of the bleeder screw, but I also saw that you can do this just with one person and you don't have to do it that way.

Please clear these few things up for me
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      07-23-2013, 08:59 PM   #2
mlifxs
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Quote:
Originally Posted by tennis_pr0 View Post
So I just have a few quick questions about bleeding the brakes. I know before you start, you should suck out the old fluid from the reservoir and put new fluid in. Now they say to never let the reservoir become empty, so how come they say to such out all the old fluid and put new fluid in?

Next, once the tube is connected to the bleeder screw and bottle with fluid in it, do I have to have an assistant for this? They say you have to have an assistant so you can yell "up" and "down" to so they can much and release the brake pedal in accordance to the opening and closing of the bleeder screw, but I also saw that you can do this just with one person and you don't have to do it that way.

Please clear these few things up for me
haven't tried it yet but I believe you can do a one person job with one of these:
http://www.motiveproducts.com/

I think you will find threads on this forum describing this product and how it can be used.
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      07-23-2013, 10:03 PM   #3
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You never suck all the fluid out of the reservoir to allow air to get in the lines from the reservoir side. The idea is to not introduce air into the brake lines, or you will have to bleed it out.

In your method, yes you do need an assistant to pump the brake pedal. But be careful, you don't want the assistant to bottom the pedal out because it could damage the master cylinder. If you're good at it, you can use a broom stick to push the pedal down, but you need to make sure the hose on the bleed screw is a tight fit on the nipple and the open end is in plenty of fluid so air will not get back into the caliper.

Bleed the brakes from the farthest wheel to the closest: Right rear, left rear, right front, left front. Right being passenger-side; left being driver-side. Pump till the fluid is clear, then as the assistant is slowly pushing the pedal down, close the bleeder screw. Repeat for all 3 other brakes. Keep an eye on the fluid level.

My wife is great at the assistant part; she's been helping me for 20+ years bleed brakes (she thinks it fun). I can loan her out for a fee...
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      07-24-2013, 01:52 AM   #4
tennis_pr0
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Quote:
Originally Posted by Efthreeoh View Post
You never suck all the fluid out of the reservoir to allow air to get in the lines from the reservoir side. The idea is to not introduce air into the brake lines, or you will have to bleed it out.

In your method, yes you do need an assistant to pump the brake pedal. But be careful, you don't want the assistant to bottom the pedal out because it could damage the master cylinder. If you're good at it, you can use a broom stick to push the pedal down, but you need to make sure the hose on the bleed screw is a tight fit on the nipple and the open end is in plenty of fluid so air will not get back into the caliper.

Bleed the brakes from the farthest wheel to the closest: Right rear, left rear, right front, left front. Right being passenger-side; left being driver-side. Pump till the fluid is clear, then as the assistant is slowly pushing the pedal down, close the bleeder screw. Repeat for all 3 other brakes. Keep an eye on the fluid level.

My wife is great at the assistant part; she's been helping me for 20+ years bleed brakes (she thinks it fun). I can loan her out for a fee...
haha might take u up on that!
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