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.

[grant19841]

Rock hard pedle, could be vac pump line is loose or broke etc.


Brake delay worn piston or fluid contaminated/old... or very low fluid.

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[grant19841]

Low fluid would indicate a leak somewhere

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[Rob69]

sounds like the valve inside the servo sticking, not releasing vacuum from atmospheric side to assist, then not letting vacuum go, holding them on, new servo needed?

[pippip]

Fluid level is normal. (I did top this up about a month ago when i got a warning on dash). It would be due a complete fluid change.

I had a look for leaks or holes, no sign of anything. Decided to let my mechanic have a quick look but cant see the car till Friday.

Tested the car again during lunch, just back and forth in parking space, and all completely fine.

Would it be strange for all of this to happen all of a sudden and then go away?

[grant19841]

Nope best get checked

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[pippip]

Yeh my initial thought was a sticking servo in which case I think it will be a new car time. Assuming a few hundred to replace that?

[Hex69]

Yeh my initial thought was a sticking servo in which case I think it will be a new car time. Assuming a few hundred to replace that?

Have you checked your plenum chamber?

Water pools there, and gets drawn into the servo, corroding it from the inside.

See here - Hard Brake pedal? Dangerous! AA couldnt find the problem Please Help! (http://www.vwaudiforum.co.uk/forum/showthread.php/140203-Hard-Brake-pedal-Dangerous!-AA-couldnt-find-the-problem-Please-Help!?highlight=plenum+chamber)

[pippip]

Thanks for that link Hex69, I'm worried now that may be the issue. I had noticed excessive condensation on the inside of the car over xmas. I even checked the foot wells but they were dry.
I'll test the plenum chamber tomorrow and see how it drains.

[spartacus 68]

Thanks for that link Hex69, I'm worried now that may be the issue. I had noticed excessive condensation on the inside of the car over xmas. I even checked the foot wells but they were dry.
I'll test the plenum chamber tomorrow and see how it drains.

There are two rubber grommets in the bulkhead. Cut them down in size or remove all together. You will probably need to shift the battery to access. Make sure you have the radio code if disconnecting.

[pippip]

Well mechanic has just come back to me and he pointed to the plenum chamber problem and sure enough he said it had alot of water in it. He couldn't get the brakes to give any trouble on a test drive but he's fairly certain the servo is the problem given the water. With the cost involved in that and 4 tyres I think I'll be trading it in.

Not a great start to the year.

Thanks for all the help folks.