2004 Jetta TDI, 125K, Pads are fine. When you pump the brake pedal 2 or 3 times it looses -for lack of a better term- power brakes. the pedal becomes Hard, like you no longer have power brakes. I have no idea how this VW works, but it's as though you've exhaused the reserve of vaccum in the brake booster and it can't replenish the supply fast enough. First pedal push is always fine. and you can ride the brakes for an extended stop without this problem happening. only happens after you've pumped the brakes 3 or so times, then you get the hard pedal and braking is SIGNIFICANTLY reduced. Any ideas? Thanks,
Loss of Power Brakes on 2004 Volkswagen Jetta TDI
by KenGar in Edgerton, MO on September 30, 2010
ANSWER by dandd on October 01, 2010
There is a vacuum pump for the Diesel Engine Jetta that powers up the Vacuum Brake Booster. I would test that to make sure that it is working at full strength. Then make sure that the Brake Booster Check valve is holding enough vacuum, it may leak or not hold vacuum properly when you apply the Brakes, so that could be why the pedal gets really hard. Here is a web site that has very good repair info for your car. http://bit.ly/mitchell_repair_manuals_online Hope that this helps!