Brake vibration 1.8t

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stang

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Ive got a 1999 1.8t quattro sport. ive just replaced the front and rear discs and pads due to a vibration when braking. pedle pulsing.
now my problem is the vibration is still there when braking.
ive removed and swaped the brakes over and checked run out. and was ok.
the only thing ive done prior to the brakes was replace the drivers outer cv joint and bothe lower arms.
ive checked and cleaned the abs rings and sensors and there 1200/1700 ohms. removed abs pcb and checked midle wire which was ok.
no abs light on dash
no wheel vibration.
ive run out of ideas now
thanks.
 
Vibration under braking is usually down to warped discs, are the parts you replaced brand new?
 
discs and pads new. checked on the works flat plate and fine.
 
All the pistons in the calipers are clean and free moving, no burst seals or anything and all bled out?
 
everything lookes fine. no leaks or damaged seals etc.
 
Does it happen at speed? Does it depend on brake pressure?

Could be ABS activating, quite common due to cracked reluctor rings and causes a pulsation thru the brake pedal, but it usually only does it at slow speeds.
 
the pedle pulses at all speeds. 1st gear just touching pedle you can feel it all way tho to 70 mph. abs rings are new on front and clean and the same. sensors are clean.
its almost as if its a warped disc. but there fine.
 
Its almost always a rear ring that breaks.

Unusual for it to pulse the pedal at high speeds though.

Can try checking wheel speeds in VCDS?

Actually, you could unplug the ABS controller and see if it goes away. If it does, you know its an ABS related issue, rather than a mechanical one like a warped disk.
 
Last edited:
Is the surface the discs are mounted to clean and flat if you spin the wheel is there any binding. Brakes can be a sod, took my brother and I 3 attempts to get mine bled today
 
audi upgrades
A4 rear calipers are a sod to bleed, air gets stuck in the handbrake junk inside the caliper. Been there numerous times!

The issue is at this point i'm not convinced its a physical issue at all.

I've had warped disks a few times, they almost never make themselves known at low speeds, usually high speed motorway braking etc. It also typically gets worse with more pedal pressure/heat, and USUALLY the whole car vibrates, rather than feeling the pulsation thru the pedal itself. My brothers car has warped rear disks an driving round town you dont even notice it. a hard brake on the motorway gives a shudder, and if you keep using the brakes hard (windy backroad or whatever) the vibration gets worse and worse as things heat up.

Which is why i'm thinking its more likely an ABS issue, When ABS activates it causes the pedal to bounce quite noticably, and if your listening you'll hear the pump fire up as well.
 
Yup. Same here. I bled mine 3 times!
The s4 ones were better a bit.
 
Its just hit and miss. I've had them bleed up perfectly first time. I've had it where it was so stubborn i gave up and ignored it for months.

The workshop manual has some nonsense in it about pre-filling the caliper and holding it a certain way to ensure the air is purged before fitting it, but fluid dribbles back out when you fit the line and get them connected up to the car etc so it doesnt really work.
 
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