Caliper Replacement - Bleeding Air From ABS Control

[2002Silver4.6is]

OK.. so $150 at the dealership got me the information that I need a $500 brake bleed with the X hooked up to the GT1 computer.

I don't get it. Why should the computer have to get involved with a simple brake bleed?? I took the X5 home and am going to do some research before doing anything. Right now my brakes work but not great.

Not too sure what my options are the indy dealer says they did what they could and they do not have the most up to date diagnostic equipment.

[fast4d]

if the caliper's pistons are not moving then you've got air in the line. at the dealer they have a machine that plugs into the abs system and cycles it as they bleed the system. I'm not sure if there's air stuck in your ABS though.

[2002Silver4.6is]

Now the rear calipers are engaging the issue now is a bit of a soft pedal. I think the cycling of the ABS is what they propose.

[JCL]

I agree that there is air in the system around the ABS valves. Pinching off the lines as was mentioned in an earlier post reduces the risk, but if you replaced the calipers and bled the fluid it is almost certain that you have residual air trapped.

This highlights one of the risks of working on modern high-tech vehicles. There are lots of posts here and elsewhere suggesting that people change their own brakes, fluids, etc, but there are potential consequences for DIY'ers. This is one of them.

This clip (I think it is from a Popular Mechanics Q&A) describes the process in general:

The secret is to not ever introduce any air into any antilock brake system. You have some air lurking inside the ABS controller's internal plumbing. This gives you a spongy pedal, prevents the ABS from doing its job properly, and may well cause the brake warning light to come on.
To rid your car of this air, you'll need a scan tool that can interface with the ABS controller. It's necessary to cycle the ABS pump and valves with the scan tool to move air along to where it will be carried out of the system at the caliper bleed bolts. Generically, this involves holding your foot on the brake pedal while telling the scan tool to cycle the ABS, and then bleeding the system at each corner. The specifics of how different systems need to be treated are quite different. You'll need a shop manual and a scan tool for the correct procedure for your truck. Or maybe it's time to throw in the towel and have a shop mechanic finish your job--if you can get the truck there without crashing.
It's possible to flush an ABS-equipped car's brake fluid without a scan tool. The operating principle is to keep the reservoir at least half full all the time. I use two assistants--one to pump the brake pedal while another hovers over the reservoir and keeps it topped up with fluid. Bleed until the fluid runs clear. Another solution is to use a compressed-air-powered pressure bleeder. Now that you've got air in the ABS controller, however, you'll need a scan tool to do the job properly

Good luck.

[2002Silver4.6is]

JCL - Thank you very much. I think that is exactly what is going on.

I feel like an idiot for not knowing the risks of removing the calipers. I do not think I have any other option than to pay the dealer $300 more bucks....

I do not think just doing a brake job without removal of the brake hoses could have the consequences that I had.

Well now we have some information that could save the next guy $450!!!!

You guys can thank me later for taking one for the team!!!

[Eric Le Baron]

Wouldn't it help if you would bleed the brake system with a large quantity of fresh brake fluid.
Like a couple of gallons?
I use the Black Label European Power Bleeder from motiveproducts.com and 2 of their bleeder bottles.
Works really well.

[2002Silver4.6is]

I know my indy dealer did a pressure bleed and said they were unable to get the system back to normal. It really seems like the BMW GT1 Diagnostic computer needs to "talk" to the ABS unit to perhaps "cycle" it to get the air out.

[Tomaz]

Originally Posted by 2002Silver4.6is

I know my indy dealer did a pressure bleed and said they were unable to get the system back to normal. It really seems like the BMW GT1 Diagnostic computer needs to "talk" to the ABS unit to perhaps "cycle" it to get the air out.

In order to "cycle" the brake system would need a loop. Each brake line dead ends at the caliper. If there is a software reset, the entire operation should take a few minutes. It appears that the Diagnostic computer is programmed to rip you off.

[JCL]

Originally Posted by Tomaz

In order to "cycle" the brake system would need a loop. Each brake line dead ends at the caliper. If there is a software reset, the entire operation should take a few minutes. It appears that the Diagnostic computer is programmed to rip you off.

While the brake lines dead end at the calipers (where the bleed screws are) there are also dead ends in the ABS controller where the valves and solenoids are. That is where the air is trapped. The "cycle" referred to is the opening and closing of the valves and activation of the solenoids; there is no loop as such in the plumbing.

The computer doesn't do a reset, which would be very quick, but rather needs to operate the valves in the specific sequence to purge the air.

I may be wrong, but I don't think this specifically requires the BMW computer, simply a scan tool with a two-way communication and the correct program to cycle the ABS controller. It is likely simplest to just pay the dealer to do the work. I don't agree that this is a programmed rip-off, simply a consequence of having a computerized brake system with air in it.

Jeff

[chubyball]

Have done many brake jobs on most expensive cars suck as Lexus and Bmw. I know when bleeding the brake you need to have the engine on running because the ECU constantly get update information from your brake sensor and etc.... I think the master cylinder does not work right if your engine is off when you are bleeding the brake.