77 530i brake booster removal???

[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? Cant get at with 13mm wrench or get a socket on it. Has anybody been there and done that?

[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.

[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.

[Mike W.]

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.

My guess would be brake fluid, not oil. Leaky master cylinders have been known to do that.

[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.