djvegas

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First i should point out i have an '86 Audi 5000s. KZ Engine. Non Turbo, Non Quattor, Non ABS

So heres my problem;

When i brake normally the car brakes fine, but when i slam on the brakes the pedal doesnt budge at all and then after about a second, starts to go down. Its quite annoying because the only time you slam on the brakes is when your 2 feet behind the car in front of you, and when you slam on the brakes and the car doesnt budge at all for a second, it gets scary. Also when i put the brake down all the way, the pedal vibrates a bit, and kicks up about half an inch.

On severe moments, that happen rarely, but seem to be much more frequent in the last week or two....

The brakes are nearly shot all together. I would SLOWLY apply brakes and it feels like it hits the bottom, and the car doesnt slow down at all, about 3-4 seconds later it starts to brake. So when this happends it feels like i have a lag of about 3-4 seconds before i can brake, i have to start slowing down for a stop sign 2 blocks in advance. BUT when i pull over and turn off and then restart the car, the problem goes away.....anyone have the slightest clue what the problem is?

It doesnt leak any hydraulic oil.

My guess is i need a new master cylinder and a brake pressure accumulator.

ANY help would be greatly appreciated, the problem is getting more severe. Would be nice to brake in time before writing off a new TT

DanA100

Yes, i would take care of the Master Cylinder ASAP. Sounds bad. ALSO ... bleed the system first. If you have air trapped somewhere it will cause a bunch of crazy things.

Will Ng

I was under the impression that only turbo cars were cursed with hydraulic boost.
If your car uses a standard vacuum brake booster, I'd suspect you need to replace it and the master cylinder.

Pedal vibration is usually caused by warped rear rotors. But if your system does use hydraulic boost, you could be suffering from lacking of hydraulic pressure from the pump or bomb.

slamming on the brakes and getting a stiff pedal at first, makes me suspect the brake servo.
Even with a bad bomb, the pump should be supplying enough pressure for one stop.
The bomb supplies reserve pressure for when the car's engine has stalled, and when the ABS pulses.

So the standard bomb test....shut off engine after 3-5 minutes, then pump the brake pedal. If the pedal goes stiff before 15-20 pumps, the bomb is dead.

SteveJ_in_TX

With the symptoms you described, you need to take the car off the road.

Now.

Why? Because not only are you endangering yourself, you're endangering _others_. And woe be unto you if the opposing lawyer found out you posted about your crappy brakes here before you hit some shmoe.

Put the car up on blocks, then pull all four wheels. Check all your pads/shoes/discs/rotors and replace whatever is 'shot'. Check your wheel cylinders for any leakage, and check to be sure your calipers are not binding. Another strong possibility is that your guide pins on the calipers are frozen, so the pressure is going only to one side of your front rotor(s).

Once you have all new or cleaned/refreshed hardware, flush all the crappy, old, nasty fluid out of your lines.

Break your plans for the weekend and do this immediately, you never know when the system will fail completely - probably when you need them the most.

the red pill

Brakes are the most vital component on a car. I drove around on my 5ktq just last month with the rear-right pads grinding into the rotor and even with downshifting to avoid using the brakes as much as possible it was still pretty scary and I slapped new pads and a new rotor on there just as soon as I could.

When changing the brakes you'll want to check the guide pins to see if they rotate and move in and out freely. I noticed on my right rear wheel the pins were frozen in place and my outer pad looked brand new while the inner pad was deep in the metal. The outside of the rotor was all rusted too.

djvegas

cheers guys, i'll take everything into consideration and check it all out. I'll curb my car for a week and use my gf's car for the time being.


Keep the comments coming though if you think of somethin

DaveN

my favorite guy was the one with the squeeky brakes, put the anti-squeek on the pads rather then where it goes, then promply drove into a tree.

srigs

Mine was slightly different. After a hard break the pedal would not do anything for half of the way down and then would engage reluctantly. When hot all 4 breaks would drag. The pistons in master cylinder would jam partial closed.

The Audi specialist said this is very common due to our master cylinder is right behind the radiator fan. He replace the cast iron one with an aluminum one for $85 for the part and $100 for the labor. A new cast iron one is $280 just for the part.

Try that an insist on the AL part its cheaper and works great.

djvegas

also with the bomb test, i hit the brakes once, and they're already stiff


am i just not feeling it right? does that sound TOO extreme?

crotext

I agree that without the "bomb" you should still have braking albeit stiff, without the problems you describe. Look to the servo and master cylinder. It's a cheap fix when compared to a front end on yours and rear end on another, not to mention the skin on your forehead and lawyer fees. Park it until it is fixed.