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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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Old 02-28-2015, 03:39 PM
jxo jxo is offline
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Location: New York, NY
Join Date: Mar 2010
Posts: 71
Mein Auto: 2000 528i
Frozen Brake Booster; Time to Replace?

A few weeks ago, my 2000 528i had a frozen solid break pedal. In 15 degree weather, with the engine left on for about 15 minutes, the pedal loosened up. I carefully drove in the neighborhood and the brakes worked fine. The pedal/booster froze up again today. Same result, the booster thawed after about 15 minutes. The brakes were fine, not mushy. I don't sense that the booster is full of water.

I am assuming I got some water in the booster due to a clogged drain but it is hard to tell how much.

I assume the booster should be replaced (probably with the MC).

Any contrary thoughts? Any safe way to determine whether the booster is safe to keep? Once it warms up a bit, I will make sure the cabin area is cleared of debris and the drain is working.
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Old 02-28-2015, 03:54 PM
JimLev JimLev is offline
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Location: MA
Join Date: Dec 2003
Posts: 4,099
Mein Auto: 540/6, S60 Volvo, Tribeca
The inside could be rusted depending on how long it has had water in it.
Might be wise to replace it. The MC should be OK.

2000 540/6 Slightly tweeked...everywhere
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Old 02-28-2015, 04:12 PM
HTK12 HTK12 is online now
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Location: Finland
Join Date: Aug 2012
Posts: 1,154
Mein Auto: E39 540i
As JimLev said, it could be rusted. If it is I would replace the booster. I see no reason to replace the MC.
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Old 02-28-2015, 04:46 PM
pshovest pshovest is online now
BMW CCA 69606
Location: DE
Join Date: Dec 2009
Posts: 830
Mein Auto: '10 535iA, '00 528iTM
Mine froze ~5 years ago. I dried it out by letting it thaw and blowing compressed air to bottom of booster thru a 1/4"OD poly tubing thru the vacuum connection. It's been working fine ever since. Not sure what to do with the booster I bought on ebay.
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