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Old 11-18-2012, 08:42 AM
robertobaggio20 robertobaggio20 is offline
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Join Date: Oct 2009
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Mein Auto: car
That's your brake master cylinder. The brake booster (the large round thing behind it) is connected to the driver's brake pedal. Your foot's force is amplified by the brake booster and directed to the brake master cylinder, which squeezes the reservoir of brake fluid that it retains, through the metal brake lines which lead to the callipers at all four wheels. This arrangement is done to increase hydraulic pressure on the brake fluid to ensure maximum clamping force is made available at the callipers, which resulted in the E34 breaking world 60-0 stopping records in the early 90s. Pardon me, I had to brag a little.

It appears that part #2 in the diagram below may be defective :

http://www.realoem.com/bmw/showparts...62&hg=34&fg=25

The diagram is deceptive : there are 2 units of part #2. You can try changing both to see if that helps.

If its the nuts which screw into them which are, well, screwed, then you have to change the entire brake fluid reservoir to which they are connected to. The diagram shows that they are not a separate part of the thing. I wouldn't advise a diy workaround on this even if it was possible, as we are dealing with very high pressures and this is a literally a driving safety issue.

That said, this is a very obscure problem that you've encountered. If you need to change the brake lines/brake reservoir, I will wager that a good used unit will do fine.

You ought to inspect everything including the brake booster :

http://www.realoem.com/bmw/showparts...92&hg=34&fg=27

...to ensure that you do not have other brake related issues.

Until you have taken care of this, please do not drive at highway speeds, and keep way more distance between yourself and the car in front than you normally would. Check and top up oil before each trip that you have to make. It is best of course that you get this sorted out at a workshop bright and early on monday morning. Sometimes there's no way to avoid the expense.

If its just a brake reservoir replacement affair, it should take a professional around 30 minutes and 1 litre of dot4 oil to sort it out. However, if you need to change your brake master pump, only buy new and of the correct brand (lucas or girling) according to your car's chassis number (or just use what is already in there). For some reason, the brake master pump and the brake booster need to be of the same brand even if the part numbers for different brands are the same, if not everything gets off. Costly lesson I learned.

The brake booster may involve around 20 minutes of work to swop out for someone who has done this before.



rgds,
Roberto

Last edited by robertobaggio20; 11-18-2012 at 08:44 AM.
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