 |
|
[quote=“jlevie” post=63723]Years ago I wanted to see how much fluid through the brake system to completely flush the system. I injected just a bit of dye into the reservoir at the MC intake ports and watched for the dye to at a wheel. I found that 350cc through the right rear wheel, 150cc through the left rear, and 150cc through each front caliper was more than enough. It really doesn’t matter whether you start with the right or left rear on an E30.
[/quote]Good info, thx.
Rob if you need a hand I will be around this weekend. Just let me know and I can come by, if only to help you do a brake pedal 2 man bleed. I once had a soft pedal after a power bleed and did a pedal bleed and it got really firm.
I’ve never had a soft pedal after pressure bleeding. But I do cycle the pedal a couple of times for the RR and RF bleeds. That will get any air that is in the master cylinder out.
I’ve never had a soft pedal after pressure bleeding. But I do cycle the pedal a couple of times for the RR and RF bleeds. That will get any air that is in the master cylinder out.[/quote]
Good to know. Are there any other tricks/steps in changing the MC? Looks pretty straight forward (famous last words). Pop off the old reservoir and brake loose the two fittings and then a good thorough bleed?
I’ve never had a soft pedal after pressure bleeding. But I do cycle the pedal a couple of times for the RR and RF bleeds. That will get any air that is in the master cylinder out.[/quote]
Good to know. Are there any other tricks/steps in changing the MC? Looks pretty straight forward (famous last words). Pop off the old reservoir and brake loose the two fittings and then a good thorough bleed?[/quote]
We just did a MC replacement on the 87 and it took some work to get all the air out of the system. What ended up working best was cycling the ABS system and that got the air through the system and out. Most of the air came out of the right rear which would have been first to activate ABS being the lightest corner. I ran it up and down the access road at VIR and had the ABS come on a bunch of times. we came back and bled it out and it was good to go. Theoretically the mc should be bench bled first but we didnt have the correct pieces at the track to do so.
Thanks for your input Andrew. Does anyone know if there’s a fancy computer trick/relay to make the ABS cycle? If not, I guess I’m going to have to terrorize the streets late at night. :pinch:
If you bench bleed the master you will save yourself a lot of trouble. Since you will only be removing the lines from the MC, very little air will get into the system and a normal pressure bleed (with a few pumps of the pedal during the bleed) should push any air through the ABS and out.
Have you changed your calipers or pads. I have seen the same symptoms with a brake pad hanging on the caliper bracket…new/rebuilt calipers…and the backing plate on the pad was actually bent on both sides. I sanded about .015 off each end of the pad and all was well. CB
More good information. Before changing the MC, I’ll go over the brake system really well this weekend.
Update -
Before changing the MC, I looked over the car a bit more. After jacking up both sides of the car, I noticed the passenger side wheel wasn’t spinning as freely as the driver side. I pulled the pads and they were wedged shaped. I slapped some new pads/pumped the brakes, went for a quick spin. I checked the wheel again and it spun freely. Could this caliper be sticking like suggested?
Pads wear in a wedge when the calipers twist. If this is a rear brake than replace the caliper bushings with brass bushings from BW. If it’s a front brake confirm it’s ATE and get the caliper bushings. If it’s a Girling front brake, swap them out for ATE and get the bushings.
How old are the wheel bearings? A wobbly wheel/rotor can knock the pads back. Then when you hit the brakes they need to travel further. Can make initial brake application feel soft.
Ok - problem solved. The old school brake bleed method > power bleeder.
Who wants to buy a new MC with bench bleeder kit? :silly:
Glad it worked out. BTW, I changed my procedure after following these recommendations at Pelican - http://www.pelicanparts.com/bmw/techarticles/Mult-Bleeding_Brakes/Mult-Bleeding_Brakes.htm
In sum, they recommend pressure bleeding followed by three rounds with the old school method.
Ed
[quote=“edavidson” post=64089]Glad it worked out. BTW, I changed my procedure after following these recommendations at Pelican - http://www.pelicanparts.com/bmw/techarticles/Mult-Bleeding_Brakes/Mult-Bleeding_Brakes.htm
In sum, they recommend pressure bleeding followed by three rounds with the old school method.[/quote]
I’ve never had a problem pressure bleeding, even from a dry system. However, during the bleed for each circuit I’ll pump the brake pedal several times. Sometimes I see a few bubbles from that, which would be a bit of air that had been trapped in the master cylinder.
When starting from a dry system, bench bleed the master. If the MC is mounted in the car. loosen the brake lines at the MC until fluid comes out.
[quote=“Rob in VA” post=64076]Ok - problem solved. The old school brake bleed method > power bleeder.
Who wants to buy a new MC with bench bleeder kit? :silly:[/quote]
How much?