I'm ready to rebuild the brakes on my 97 M3 that's equipped with ABS and ASC. The Bentley manual warns readers (and DIY's) that this should be done by an authorized dealer. Is there something that I should be aware of before I start, or can I proceed using good common sense and a fair amount of experience with lots of brake work? Thanks for any advice in advance, ---- Mike B.
Afaik, it's nothing unusual, just don't let the lines drain out. If you're pulling the calipers, cap or do something to keep the fluid in the lines; I think the problem arises if you get air through the system and into the abs/asc unit. Avoid that, and I'd think you should be able to bleed like normal.
There is also a trick that cycles the ABS by pulling the relay and shorting to pins. To cycle ABS, pull the ASC relay from the fuse box under the hood. It is located on the firewall on the driver's side. Jump pins 30 and 87 (look under the relay to figure out which pin is which) using a jumper wire with spade terminals at each end, you should hear the ABS cycle.
Nothing to be worried about like mentioned above just make sure the system doesn't run out of fluid during the repairs. Air in the system is really a pain to bleed back out. If you do wanna jump the relay just make sure to use a large enough gauge wire so you don't melt the fuse box. Investing in a pressure bleeder may not be a bad idea either, makes bleeding much easier and a one person job.
Many thanks for the information. Steel brake lines are included in this brake rebuild but It sounds like if I minimizing getting any air in the lines I should have no issues. In the event that I start bleeding the brakes (yes I have a power bleeder) but find that I'm having a difficulty removing all of the air from the system, would by passing the ABS relay with the jumper wire help with bleeding the system?
When my hard lines were replaced I found it necessary to enlist my wife and do the two person method to bleed. It took a few times to run fluid through the lines until I felt comfortable. I wasn't happy using the vacuum method.
As long as you keep fluid in the lines from the reservoir to the end of the line (& thus no air in the ABS unit), actuating the ABS solenoids shouldn't be necessary. Similar to Steven's experience, I've gotten a better bleed using a pressure bleeder vs. a vacuum unit. If you don't have a 2nd hand to enlist, if you ensure the end of your bleed tube is submerged in brake fluid, you can add some pedal pumps for some positive displacement pressure - if the tube end stays submerged, you won't draw air back into the calipers with the pedal return. I've used my phone camera to record the bleeding to doublecheck for no air bubbles you might see when pumping the brake pedal. If you have an old master, don't pump it beyond your normal pedal-actuation range, you could blow the master internal seals if there's any rust on the master piston; flooring the brake pedal (probably) isn't a problem if your master cyl. is new or not too old.
Thanks for all of the input, your comments and suggestions were very helpful. I installed the new SS brake lines but was very careful to minimize any air into the system by loosening the connection farthest from the caliper then capping the line with a rubber cap. Then I installed the brake lines on that wheel, removed the cap and connected the line and lost very little brake fluid to that wheel. Obviously the back wheels were a little bit more challenging and the car needs to be high enough on your jack stands so that you can get underneath that lower control arm and see the brake line connections. I bled the brakes with a power bleeder and had no problems getting a firm pedal. Use your head before you grab the wrench and its a pretty straight forward job. Again thanks for all the input.
