77 530i brake booster removal???

Post your E12 technical questions and comments here. Please, no off-topic posts.

Moderators: Mike W., Pierre

Post Reply
canada karl
Posts: 1065
Joined: Tue Jan 06, 2009 3:50 pm

77 530i brake booster removal???

Post by canada karl »

How in the world do you remove the bottom nut on the stud that holds the booster on? The bottom one on the drivers side in that inaccessible hell hole? :x Cant get at with 13mm wrench or get a socket on it. Has anybody been there and done that?
1976 530i. BMW 59 Triumph TR3A(rolling resto). 67 Triumph TR4A(salvageable). 86 900S Winter car
User avatar
Robert Bondi
Posts: 371
Joined: Sun Jan 11, 2009 12:33 am
Location: Austin, TX

Re: 77 530i brake booster removal???

Post by Robert Bondi »

I haven't been in there in a while, but it is doable. A starter or half-moon wrench is probably perfect for that, IIRC. Those curved handles are so useful in so many spots.....starter, exhaust nuts, clutch slave cylinder, guibo coupling, the brake booster....anywhere you need to sneak around/behind a curved obstruction.
Robert
77 530i
77 Euro 528
canada karl
Posts: 1065
Joined: Tue Jan 06, 2009 3:50 pm

Re: 77 530i brake booster removal???

Post by canada karl »

Thanks for the tip. I 'll buy one of those half moon wrenches. In the meantime I cut an old 8" wrench in half and used the 12 point end on the nut. When I got the booster out I was surprised to see it 1/3 full of oil. I probably had the vacuum one way valve in backwards at one time? Found a spark plug on the frame rail that someone probably dropped in the cave of doom below 30 years ago and cursed his luck. :lol:
1976 530i. BMW 59 Triumph TR3A(rolling resto). 67 Triumph TR4A(salvageable). 86 900S Winter car
User avatar
Mike W.
Posts: 2817
Joined: Wed Aug 30, 2006 12:12 am
Location: Sonoma County

Re: 77 530i brake booster removal???

Post by Mike W. »

canada karl wrote: Wed Jul 17, 2024 1:27 pm Thanks for the tip. I 'll buy one of those half moon wrenches. In the meantime I cut an old 8" wrench in half and used the 12 point end on the nut. When I got the booster out I was surprised to see it 1/3 full of oil. I probably had the vacuum one way valve in backwards at one time? Found a spark plug on the frame rail that someone probably dropped in the cave of doom below 30 years ago and cursed his luck. :lol:
My guess would be brake fluid, not oil. Leaky master cylinders have been known to do that.
Mike W.



02 525ita. Wife's, aka grocery getter
02 530i. New to the fleet, 3 pedals.
03 QX4, AKA the Datsun. Finally got the 4WD vacationmoble to stop smoking.
07 Xterra. Still on the DL, a purchase from hell.
User avatar
528i-1981
Posts: 570
Joined: Wed Feb 07, 2018 5:50 am
Location: Franklin, TN

Re: 77 530i brake booster removal???

Post by 528i-1981 »

This actually points to a question I've had - does removing the threaded connector to the vacuum line give access to where the fluid would accumulate? I've always wanted to check for fluid but am in no hurry to take everything apart. It seems like the whole front of the booster housing is on one side of the diaphragm.

Evidently having a little fluid in there doesn't create huge problems? I replaced a pretty crusty MC a couple of years ago but didn't inspect the booster, so I've always wondered if there's some old (hygroscopic) crud sloshing around in there.

I'm thinking a syringe with tubing could evacuate it if that's where access can be gained?

Karl, FYI, Ireland Engineering has a rebuild service for US$250 if you need it. It comes back pretty.
(oo=00=oo) Eric
1981 528i Manual
Post Reply