BMW Stiff – Hard – Brake Pedal – 1, 3, 5, 6, 7, X3, X5, Z4 Series
car year: 2005
car model: 545i
I recently changed out my vacuum pump after reading blogs about the hard brake pedal and plus it was leaking oil, well the problem is still there and the brake is still doing the same thing. i even pulled the hose off the vacuum pump to check the in line check valve. at this point i don’t know what to do, can u shed some insight. thanks
The late model BMWs that have the “N” series V12, V8 and 6-cylinder engines (most 2004/06-on BMWs and some earlier models) with the Valvetronic variable valve timing system, use an engine driven vacuum pump to supply vacuum for the power brake booster. The brake booster works similarly to a common vacuum operated power brake booster with the exception that the vacuum is originated by a pump rather than via intake manifold vacuum.
A somewhat common problem with these systems is a hard, or stiff, brake pedal. The diagnosis is typically either a faulty vacuum pump or a faulty booster. A few years ago BMW did perform a recall on various V8 & V12 models that use this system. The recall replaced the vacuum pump (due to leakage) and if oil was found in the vacuum booster, the booster was replaced. Now, a few years after the recall, we are seeing a common issue with the boosters failing, on all models (6-cylinder, V8 & V12), as well as continued pump failures. Sometimes there is oil in a failed booster, but not always.
Since you have already replaced the vacuum pump, and you are still experiencing the firm pedal, it is likely that your booster is faulty.
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