DIAGNOSE THE PROBLEM - all connected?

[polecat]

Audi RS4 B7 - 2006. 60,000 Miles - Brand New Conti Tyres all 4 corners, less than 1000 mile on em. Brand new rear discs audi, yellow stuff pads, front discs 5000 miles from new, skimmed less than 1000 miles ago, new yellow stuff pads at same time. New braded hoses all round, top spec brake fluid, and racing hydraulic steering fluid -top spec

Problems - all of these things happen intermittently, then sometimes all together - but usually one or the other symptom manifests,

On braking, intemrtnet brake judder through steering wheel, slight wheel pull, although not at every time I brake,

On braking, intermitent violent JUDDER through left side of car cabin, rattling seats etc - absolute brake fade at high to moderate speed, even at warmed discs or from cold.

On braking now and then, the stoppers actually stop me, damn quick, less frequent than they actually do not stop me though.

Steering wheel feels quite light, with, slight play.

A grinding noise seems to be coming from left side front wheel area, if as though calipers were not fully disengaged, and this becomes more noticable on a smooth surface or when I turn the wheel or go around round abouts, over time its getting louder,

On reverse and full lock, bit of a grinding noise coming from left front end wheel area.

General increased vibration in cabin


Before any tit says torch the car, ive already thought of that, and im not allowed to play with matches.-

Any diagnosis of collective problems and or similar experience what it can be?......I /we have our suspicions and its a process of elimination, expensive elimination.

tHANKS
p cAT

[adsgreen]

Hmm

My 'gut' feel is a sticky piston, calliper or pad.
If the pad isn't disengaging from the disc properly then it'll heat up.
If its only one side then that side will work much faster than the stone cold one.
This can cause pad material to build up on the disc giving the effect of a warped disc (wobble through steering wheel at speed and light braking)
If this goes on for too long the pad will overheat and start boil the fluid giving massive brake fade.

Here's what I'd do:
Jack the car up and spin the wheels by hand. See if something is fouling or similar.
Start the car up and ask somebody to apply the brakes as you spin the wheel to see if the pads are sticking.
Note- disc brakes do make a grinding noise as they do just hover over the disc. What your looking for is differences between the wheels.

The rs4 discs are floating - did they take off the disc to skim or do insitu? Wonder of they didn't torque or skim the discs properly so they are skewed / running out.

Finally take the pads out and look at them - if they are overheating you can sometimes see the effects on the pad.
Oh you could also drain the brake fluid to see if it's gone a funny colour. I've seen fluid go a bit sludgy after brake fade on track.

[polecat]

THANKS - interesting, and along the lines pretty much for one of the problems - sticking piston.

Discs were taken off and skimmed, im not too sure what the measurement readingsare are now though.

[PhilT]

Might not be it, but wheel bearings are consumables too.

[polecat]

Phil, cheers, exactly in part, some of the symptons are mimicking a wheel bearing - in fact classic signs,,,,,,which also could be brakes, but this is the dilema I have, and discussed with mechanic, process of elimination, what collectively, and or independently is wrong, which I must get to the bottom of, before I crack up, as its no joy to drive the car.

personally - I believe there are 4 faults to the car - 1 Caliper sticking, pad clogging, identified by Adsgreen, 2 Wheel bearing, the grating noise etc, Phil T - lets see what else anyone can I dentify.
Thanks - P Cat

[P_G]

Have you identified whether the judder is coming from front or rear discs?

I would say the same as adsgreen, sticking piston / misfitted pad causing pad build up if the discs are skimmed true. There are not many people who can skim floating discs without making a block to bolt the disc on to to skim it. Could be that the rears have pad build up on them hence why I asked the question of whether it is fronts or rears that judder. If you can strike out disc / pad / caliper issues then it is on to brake fluid and proper bleeding. Supposedly this need a VCDS linked machine to do it properly to counter the ABS but it can de done normally. Failing that then bearings. May want to check wheels and tyres are true also.

[polecat]

PG - I believe you are taking your car down to Revo in Dunston next week?...............let me know when, and you can have a drive and see for yourself,,,,,,,,,,ask Glenn Copeland, the only consistent aspect, is the inconsistency of juddering etc, and it doesnt do it, then it does it, wheel woobble, then no wheel wobble - the only constant constant, is the wheel type grinding noise, which I thought sticky piston or bearings grinding.

at 60% of the time, I say judder from front, then, when it violently judders, its from left hand side, passenger seat backwards, 40%, whole left hand side, feels like the car is going to vibrate itself apart, travels through steering wheel, handbrake, seatbelts, seats rattle. its awful, and I hate the car, as much as I love it, if you know what I mean.

I have read that to check warped back discs, you need to carefully apply light handbrake, while travelling v ery slowly, avoiding flipping car, to see if judder comes through handbrake, but article I read advised, get a 2nd person in car, to lighly do this, knowing the biting point not to knacker hand brake.

everything is pointing to piston sticking, pad, maybe rear disc/pad, but im convinced too, it is a bearing also,,,this giving me at least 3 problems isolated, which all come together and mimick a similar problem.

Thanks for response - Graham........im thinking on a manifold clean as you had, but obviously wont do anything until all this sorted, just not fun to drive anymore.

Cheers Martin... AKA - Polecat

[lma07]

I've suffered from a wobbly sensation. Had my front discs/pads changed as I had warped discs. 6 months on I felt the same problem. Took it to audi and they said all 4 of my alloys were buckled. After getting a 2nd opinion on my wheels they were indeed buckled. So £2400 later I had 4 new alloys from audi. I thought it was time to put on New tyres. Put on New front and rear discs and pads, brake fluid change and car feels like new again. Skint now though

[mondo2126]

i had similar problem on my 1st rs4 after 2 sets of discs in 2 weeks as the vibrating persisted they found out the hub was not running true, replaced hub problem solved

[P_G]

I've suffered from a wobbly sensation. Had my front discs/pads changed as I had warped discs. 6 months on I felt the same problem. Took it to audi and they said all 4 of my alloys were buckled. After getting a 2nd opinion on my wheels they were indeed buckled. So £2400 later I had 4 new alloys from audi. I thought it was time to put on New tyres. Put on New front and rear discs and pads, brake fluid change and car feels like new again. Skint now though

Were they so buckled they couldn't be straightened? I had buckled alloys as weel (could see them on the dyno and had them straightened for less than £50 per wheel when they were being refurbed.

[lma07]

I've suffered from a wobbly sensation. Had my front discs/pads changed as I had warped discs. 6 months on I felt the same problem. Took it to audi and they said all 4 of my alloys were buckled. After getting a 2nd opinion on my wheels they were indeed buckled. So £2400 later I had 4 new alloys from audi. I thought it was time to put on New tyres. Put on New front and rear discs and pads, brake fluid change and car feels like new again. Skint now though

Were they so buckled they couldn't be straightened? I had buckled alloys as weel (could see them on the dyno and had them straightened for less than £50 per wheel when they were being refurbed.

I have arranged for them to be sent away to see if they can be repaired. Would be handy to have a full set for winter wheels. Still to hear outcome though.

[P_G]

Laura, my local Wheel Specialist straightened mine but they have Alloyfix round the corner for more heavyweight work if necessary including alloy welding should they crack the alloy when straightening it. Would recommend either, the former is a franchise so may be near you.

[lma07]

Thanks for the info. I've still got them so I'll look at getting them repaired