Re-plumbing Brake Curcuit around ABS

[Z3_GoCar]

I found out the reason I've been having issues with flat-spotting. My brake system is in fail-safe mode. So how do I replumb around the ABS valve? Will I need a new proportioning valve? I'm dealing with a BMW four wheel disc's, so I won't need a residule valve like a drum system. Looks like just unpluging the actuator isn't cutting it with this particular system. How about the legality of a replacement master, if I can't get a proportional valve to work correctly?

James

[JeffYoung]

Circuitry -- in my view, all lines, valves, etc., is free. The m/c must remain stock.

ABS can be removed, correct?

Any way to just use the stock master, and then do all your own lines to the calipers? Just plumb in a prop valve in teh rear line to get balance, and at least in theory you should be good to go.

Get one of the good flare tools though, Imperial from Eastwood or the equivalent (about $300). The cheapies from autozone just suck ass.

[JoshS]

James,

How do you know it's in failsafe mode, and what exactly does failsafe mode do?

I, too, have flatspotted two tires this season. It's expensive.

Josh

[Dave Ebersole]

I replumbed / eliminated the ABS on an Audi 90 Quattro street car once. Your Bimmer still has to have a dual circuit M/C so it shouldn't be too big a deal (easy for me to say).

[buldogge]

Hey James... It's relatively easy on the BMW. The master has two lines running down to the ABS pump, F+R. The factory plumbing uses a 'T' junction at the rear of the car. Purchase a spare 'T' at the dealer.

Remove the ABS pump and put a 'T' between the two lines for the front calipers connecting to the single front line from the master. For the rear line either order a 10mm bubble straight coupler...or...add your proportioning valve by running a new line from the master into the cockpit and bend the rear line to meet it.

Good luck...

[Doc Bro]

James,

We found and solved that problem on the Z. First time we fixed it similar to how Buldogge described. This winter we just redid the system like Jeff had described to clean it up and remove a couple of extra unions. Both will work.

R

[Z3_GoCar]

Thanks,

I'll send this to Kevin, who's working on it as I type this.

James

ps. Josh, the pedal is really soft then firms up hard. I didn't realize that it was in fail safe mode myself. It seems the ABS pump needs to be plumbed around. It's funny because I was able to learn to brake around it on the RA-1's.

[JeffYoung]

Some notes on my replumbing adventures:

1. Get a good flare tool. Cheapies from autozone don't cut it (see 2 below).

2. If the flare looks bad, it probably is and will leak.

3. Do not use compression fittings.

4. Understand the type of flares on your car -- bubble or double?

5. STainless steel lines are not worth the added cost, and are a bitch to form into flares (see 2 above).

6. Plan out your lines before flaring and adding fittings. Will save you that shitty situation of being 2 inches short with a long line that you spent 2 hours bending to fit.

[Z3_GoCar]

It seems I had mutliple issues as the master wasn't working correctly. The car had sat in Ohio for a few years before I purchased it, so maybe mositure had worked into the master. I flushed it last season and then Kevin flushed it again, but moisture isn't a problem where I'm at, so as long as I keep it flushed a couple times a season it should be fine. I had Kevin go ahead and replumb it with an adjustable bias valve so we can set it correctly now.

James

[chuck baader]

James, I did everything to my car...new master cylinder, front calipers, all new lines, even a different bias valve.(by the way, I used the emergency brake tube to run the line to the rear "T") I still chased a hard/soft/funky brake pedal. Finally I replaced the brake booster...AMAZING the difference!!! Also, since anti lock brakes are specifically disallowed, pitch the control unit and associated wiring. In addition, the stock E30 circuit had a pressure reducing valve in the rear brake circuit...remove this if you don't run a dedicated line from the bias valve to the rear "T". Chuck

[Knestis]

FWIW, on the Golf we finally went to separate lines from the MC to the back wheels, with lever-type prop valves in each, independently. We initially did the T thing off of one port on the MC after we took out the ABS, and the feel was never good at all. It's lots better now.

K

[Z3_GoCar]

I'll have to check out the vacume booster when I pick it up. I'll also check for the restrictor valve in the rear line. Thanks for the heads up.

James

[JoshS]

James, I don't think you have a rear restrictor valve, or a "T", although there could be a difference between '98 and '99. Mine has two independent lines going to the back, one for each wheel.