Brake pedal intermittently hard/ poss servo problem?

[leigh72]

Hi all,
My A4 tdi 130 sport, has twice had the issue of the brake pedal going hard, as if the servo has failed. If it's left for 10 mins the pedal works as it should (I have had the servo replaced a number of years ago when it failed completely, that time the lack of vacuum effected the performance of the car as well).Obviously I want to sort this out soon, as I don't want the pedal to go hard when I need it, but don't want to buy a new servo if it's something else. Also I was told that vw passats of similar age had a recall on the brake servo but the A4 didn't. I have checked for any lose pipe work etc but all seems ok, the only thing I could find is that the scuttle around the servo was half full of water - thanks to a blocked drain hole, could the water have entered the servo at all? Any ideas work be gratefully received.
thanks in advance.

Leigh

 

[quattrojames]

I suspect that the water in your servo is the problem. Often it freezes (where are you?) and as it melts pedal feel is regained.

 

[Steffgj]

As James said. Had this exact problem... took the servo out and it was basically rusted through. The pedal was always solid after a cold night and also used to lose servo assistance randomly now and again (not fun). New servo was the only solution.

 

[leigh72]

Thanks for the replies both of you, i'm in wrexham, north wales James where we had no proper cold temps for a while, but both times its occured has been during a journey and not when the car is cold. Anyway I have picked up a decent seconhand servo just in case and will take a proper look at the one in the car this weekend.
Cheers
Leigh

 

[Cabbyfan]

When my B6 saloon did this it was the servo caused by the dreaded plenum chamber and water ingress.