Brake Problem

pippip

Hi folks,

Think this may be the final nail in the coffin for my car.

02 Audi A4 b6 1.8T (150k miles)

Driving yesterday in bumper to bumper traffic and brakes seemed extra sensitive as in brakes coming on too quickly. And when i took my foot off the pedal there was a 2sec delay in the them letting go. As I went on this got worse to the point at next set of lights I had to fairly rev the engine to get it moving and this continued until I reached about 20kph then they completely let go of the wheels.

Being wary i saw a slow down far in the distance and went to slow down only to have no brakes, couldn't push the pedal at all, rock solid. As I continued and was about to park at the side of the road I tried them once more and all complete perfect again? Stayed fine until i reach my destination a very short distance away, all perfect as I parked.

Anybody have any idea what might have been the cause?

Car is parked up now and haven't been back to it (bus was not fun).
Given the car is 02, worth about €1000-€1500 max, nct next month, needs 4 types possibly more minor repairs. I really feel like its time to get rid of it but would like to know what the brake problem may be.

jca

Servo sticking maybe? The very hard pedal would be a sign of servo trouble, it could be something as simple as a split/perished vacuum hose going to the servo. Start the engine and listen around the servo area for hissing. Is the car running ok otherwise? Usually a split hose of that diameter will give idling problems too.

pippip

I'll go out and have a listen under the hood.

Car is running fine apart from cold starts, I actually started this thread a few weeks back but it had started behaving since.
http://www.boards.ie/vbulletin/showthread.php?p=98018164

Once running a few minutes all is good, no abnormal engine problems or performance issues.

pippip

Tried it just there and car is running smooth, no sign of leaks or hissing noises.
Went back and forth in parking spot and all fine, nothing strange with the braking at all, absolutely perfect.

I'm thinking a sticking servo too. I suppose that would be couple of hundred for parts and labour?

jca

I had a look at your other thread. I think you're getting an intermittent vacuum leak which is why it's difficult to start when cold. Try and have a look around the crankcase breather setup, if that's gummed up it could be the source of both problems. Don't be afraid to bend and squeeze a few rubber pipes with the engine running, as soon if you find the dodgy hose the engine note will change, revs will increase as the mixture leans out. Obviously take care not to have anything hanging from you (neck tie, long sleeves/hair etc.) that could get caught in the moving belts, fan.

pippip

Cheers for that. I'll have a good look tomorrow and examine everything as you suggest.

Waterson

Very good advice from jcan there. Those 1.8T have a really complex vacuum hose setup complete with one way valves which may stick closed intermittently. A vacuum leak could be checked with a spray bottle of water, with engine running spray water around hoses and brake booster and listen for a gurgling sucking noise that would indicate a leak.

pippip

Mechanic got back to me today. Two test drives and didn't experience any irregular braking...typical.

Anyway he did a bit of research and turned up the same info I had come across. Plenum chamber under windscreen blocked, he found water in it which we are assuming worked its way into the brake servo. Said all the calipers and lines looked fine so all pointing to servo.

Looking at a quote of €350 to replace. Happy enough with that. Going to get a pre nct check first with him before I give him the go ahead.