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Most brake boosters have a method of adjusting the push rod but I don't see it here. The reason I want to adjust is because the calipers are locking on.

Hi Mike I just measured the depth of the rod and it appears to be on spec at 1.92" so My theory that the rod is not adjusted properly is probably wrong. I do hear the air hissing coming from the booster so I believe the booster has failed. Can the booster fail and intermitenly lock the brakes on? My understanding is you can still drive with a dead booster but you have to press harder on the pedal. I can drive sometimes and stop by applying extra pressure on the brake pedal but sometimes the brakes do lock up? Would the brake lock up be normal for a failed booster or is something else going on. Karl

The measurement spec if fine, but what's important is that there's some free play. Not a lot, but some. You can't have any preload on the M/C at all.

I've been seeing some of this on Mye28.com and it seems to be caused by a bad M/C. Not quite sure how, it's not that complicated a device, maybe a plugged port or something in it. They do still seem to be available, but rather expensive. Now being the cheap SOB I am, if it's not out of adjustment I'd buy a kit and rebuild it. Coming from Latvia there's some on ebay for not a whole lot of money. On the other hand, if your M/C is rusted and pitted, a new kit won't last long if at all.

https://www.ebay.com/sch/i.html?_from=R ... 3&_sacat=0

On the booster, correct, a leaky booster will first manifest itself by not having a residual stop or two after the car is shut off, then if bad enough not providing enough or even any boost, but not automatic braking, just lack of boost.

could it be as simple as old brake hoses that won`t allow fluid to flow back...? Or are all brakes locking

dutch Stainless steel brake hoses. did you ever get your brake booster issue sorted out?

Mike I do not know how the 0.020" clearance is to be set. The brake booster on the 530i is like a big cavern. I was able to disconnect and pull back the MC enough to see inside without disconnecting the brake lines. I'm new to working on brake boosters but I assume the push rod would have a lock nut that would have to be undone to adjust the clearance.....how a person would access it way back in there beats me? Or the push rod is simply turned in or out by hand, I'm going to put a boroscope in the cave to see what's going on in there. Most of the videos you see on the Internet on how to adjust booster push rods do not have an MC like the 530i that has a 3" metal tube protruding from it. The MC was rebuilt. Best thing I can do is contact the guy I sold my 76 530i parts car to get the booster of it. It seems there was a change in the booster set up from 76 to 77.

I`m not sure about the 530i booster but on my 528 it looks like it can be adjusted by disconnecting the pedal from the rod , loosen the counter nut and turn the fork in or out.

Thanks for the info. I will have a look
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