Get Boosted! BMW 3-Series E36 Brake Booster DIY

Maybe your BMW’s brakes have you scratching your head the way ours did. After years of reliable, solid braking performance from this BMW part, our brake pedal had degraded into a soft, mushy mess usually around the 2^nd braking zone of a track event. We first noticed things were awry last year but this season it turned for the worse – leaving us essentially devoid of brake feel. As we don’t need to tell you, the BMW community is big, and a little digging turned us on to a curious finding – after 20+ years (23 in our car’s case), The BMW e36 brake booster (like many others) go weak – not actually failing but frustrating those of us who demand the performance of high quality and fresh BMW brake parts. Get your new BMW 3-series E36 brake booster.

With essentially every other BWM performance part new or refreshed in our braking system, we decided to undertake this straightforward if messy repair. It worked out great, after the fix below, the brake pedal provides excellent feedback that we need on the track. Full disclosure, while our brakes are back to their BMW OEM glory, we’re unrepentant fans of a firm pedals and will be exploring a big brake upgrade in the future (that will benefit from the new brake booster).

While some consider ditching the brake booster entirely, doing so almost always loses ABS (and requires re-piping the brake lines). We tried several races without ABS and found that our tracks are just too bumpy – critical time was lost in a corner or two at each of our local tracks.

Remove as much fluid as possible from the BMW’s brake reservoir with a syringe or turkey baster
Disconnect or cut the BMW vacuum hose and clutch/ABS brake hoses running to reservoir. Be prepared for spillage. Also remove electrical connectors from BMW parts such as the reservoir cap and brake booster.
Using flare nut wrenches, disconnect the BMW brake lines from master cylinder. Tip: use rubber caps for ends of closet racks (available at hardware stores) to cap off open brake lines. Loosen 2 nuts affixing BMW master cylinder to brake booster and remove master cylinder. While some suggest leaving the master cylinder attached and removing them with the brake booster, we found it was far too tight to do so because of the ABS pump.
Remove clevis pin attaching brake pedal to booster and 4 nuts securing booster to firewall.
Disconnect BWM brake lines running to ABS pump. Loosen single nut at lower front of ABS pump. Remove electrical connection and remove ABS pump by pulling up and away with the front of the pump.
Remove the BMW e36 brake booster like it ain’t no thang. Use screwdriver to pry out circumferential wire that hold pedal sensor into old booster – you’ll reuse this.
Remove your nasty old transmission parts like the BMW clutch feed line that runs through firewall and to clutch master cylinder. Access to this is nigh impossible with the booster installed, so if your booster is original, chances are so is this line. Order a new BMW clutch reservoir hose. Now’s also a great time to replace the BWM feed lines to the ABS pump since I already tricked you into cutting them and the braided hose.
Install the new BWM e36 brake booster and reinstall ABS pump and hard lines. It’s a good idea to also install a new check valve.
Fit new brake booster seal and reservoir grommets, reinstall reservoir on master cylinder (sealing plug and O-Ring)
“Bench bleed” the BMW’s master cylinder. The quotes are because you do not want to do this on a bench – install the master cylinder to the booster in the BMW and connect the ABS and clutch lines to the reservoir first. Then, hook up a bench bleed kit to the two master cylinder outlets and have your driver make screeching sounds while slowly operating the BMW’s brake pedal (3 seconds in, 3 seconds out) until all air is evacuated from the master cylinder.
Reinstall the BMW’s brake lines to the master cylinder and bleed the clutch and brakes thoroughly. Extra credit: while bleeding, activate the ABS by jumping Pin 30 and 87 under the ABS relay or just go terrorize your neighborhood by engaging ABS repeatedly and make sure to give your system one last courtesy flush after doing so – you’ll likely get a few more bubbles that were trapped in the ABS pump.