2.0 fsi brake pedal

[vinnoh]

Hi, the brake pedal on my 2005 2.0fsi when engine is started starts to drop to the floor. To the point that the brakes engage on their own. You can depress the pedal when it's running and the pedal stays down, you have to lift it with your foot to disengage the brakes. I have been advised that this is relatively common, but it can be any number of things. I would like to get some real opinions as to what it may be. I am leaning toward the power booster, but that means the vacuum would be on the wrong side to create the issue.

[Crasher]

Manual or auto?

[vinnoh]

It is a 2.0 fsi auto tiptronic

[Crasher]

Yes I thought it may be an auto, these are often fitted with an electric vacuum assist pump in addition to the mechanical one and the system can over assist. You may be able to hear the electric pump running, pressing the brake pedal repeatably should tigger it so difference means it may be stuck on.

[vinnoh]

Thank you, very helpful. So this means that the pedal will for the want of a better description (suck its way down to a brakes on situation?) alternately stay on when pedal depressed?

[Crasher]

Could yo private message me the cars VIN?

[Crasher]

Yes you have the electric booster pump as your first post made me suspect, it may be running too much as actually sucking the pedal down. You need a VAG specific code read now to see if anything relevant is stored and there is a vacuum sensor in the system so the actual values can be read and there may be a pop value if VCDS is being used. Unfortunately in the UK that car and engine (BLR) are very rare which is a shame as it is much better than the 1.6FSI we have to put up with.

[vinnoh]

Thank you. On to it now, I don't have a VCDS so I have dropped the car to a local specialist to look at. Hopefully the fix is relatively simple.
Having a timing belt kit through it at the same time, it's a wee bit overdue. Cant find a record of it ever being done. It only has 74000 kms on it but should have been done a couple of times during the last 15 years.