I have a '97 A4 1.8TQ with 55k miles. This morning after driving about an hour at highway speed my brakes failed when applied as I exited the highway. The air temp was a crisp -14 deg f. The pedal felt as though it would not compress and I came to a stop by driving onto the shoulder up a long uphill exit ramp (fourtunate). I then drove very slowly trying to pump the brakes and they started working normally again after 2-3 minutes.<p>The dealer service folks have found nothing wrong yet. I assume something froze. Anyone have an idea what would freeze and how I might prevent it in the future?<br>Thanks!

have you had the fluid changed? could moisture have worked its way into the sysem and frozen<br>in the lines?

I find the 4 disks get wet very easily, especially with (very open design) after-market rims. The first time I hit the brakes after being on a wet highway there's nothing there until it dries out.<p>Is it possible there was ice on the disks or the pads after a long highway drive at that temp? This would explain why it's working now and the dealer can't find anything.

Along the lines of the "unabimmer", possible other causes is loss of vacuum boost. Vacuum line might have frozen.

After about an hour @ -5 or so my pedal wouldn't depress at all. Luckly I came to a stop and pumped a few times and it came back. Very strange and mine is brand new!<p>-mikep<br>99 1.8TQSTip Wett