Worrying Wobble

[Mark Elder]

Couple of weeks ago I was driving along at no great pace when I noticed quite a wobble in the steering - definitely coming from front of car, bit like really bad wheel balance but I was only doing about 40. It did not go away with speeding up and down (except it got slower or faster) - so probably not balance. Road I'm familiar with so probably not the road.

Seemed to be getting worse so I started looking for some where to stop, then I went around a roundabout and the problem vanished (it had lasted for a couple of miles).

So I just thought the road must have been affected by the hot weather and I thought no more about it.

This morning it started again (different road and again one I know). Similar symptoms. There is no noise associated with it. Again after a couple of miles it just faded away and it did not happen again in rest of my journey (another hour). Had a good look around car when I parked up and nothing obvious is wrong.

Any ideas what it might be?

 

[cd1957]

The most common failure for this sympton is,the rubber dampers between steering rack and track rod.Jack the car up and try and turn steering,you may find about 3inches of movement if damper fails,sometimes it will lock back in position.

Chris

 

[clyde]

Check your front pads aren't binding on Mark.

I had this not long after I got the car and had it into the OPC a couple of times but they couldn't find anything wrong with it (didn't charge me though which was nice). It happened sporadically and for no apparent reason. I eventually sussed out that when it occurred the whole hub area got incredibly hot and I think (but never managed to confirm) that this did something really weird to the ABS sensors which then caused the pulsating feeling I suspect you're getting. I always stopped quite quickly after it started so don't know if it would have went away by itself, however, if I stopped for say a minute or so and started off again it would have gone.

Corrosion behind the stainless steel plates in the callipers prevents the pads moving off the disc as they should, resulting in them (sometimes) rubbing and eventually overheating. A quick fix is to grind the backing plates down so they are smaller and able to slide. Extreme I know but OPC's do this, or at least used to. A proper fix is to remove the plates, clean the corrosion off the callipers and fit new plates. I got an indi to do this because I didn't much fancy the thought of trying to sort it out if I snapped one of the small fixing screws or rounded the cross-head.

 

[A Ward]

Definintely worth jacking the front end up and check your wheel nuts/studs and also rocking the wheel itself to see if there is any play in the wheel bearings - best to do this cold as it could be masking the problem when warm due to thermal expansion - hence why the problem goes away after driving for a while?

 

[JB 3.2]

Mark, I have exactly the same problem. My local independent was unable to find excessive play in wheel bearings or suspension/steering bushes. I had the front wheels rebalanced followed by 4 wheel alignment but the car doesn't feel any different in normal driving.

At the MOT they suggested brake discs were corroded on the inside face so these have now been skimmed and at the moment the vibration has not returned but I'm not totally convinced it has been cured.

I have a feeling that certain coarse road surfaces may start the vibration but thats as far as I've got.

Will watch the thread with interesr, trust its not a repeat of loose wheel nuts again.

 

[nfearn]

It is also possible (albeit reasonably unlikely) that the front tyres are worn unevenly around the circumference - i.e. along the length of the circumference so that they take on the appearance of a 50p piece viewed face-on, though not as pronounced of course.

Spinning the wheels with the car jacked up should show up this kind of wear.

When I had this on an E39 5 Series it was also accompanied by a bearing-like drone at motorway speeds. The cause is, I would guess, a combination of tyre construction and damping.

Good luck with finding the solution.

Nick

 

[997GT3_KO]

Check that you dont have a slow puncture...?

 

[Mark Elder]

Wow - thanks for all the suggestions!

My disks are definitely corroded and do create a (much lighter) wobble under braking - I'm about the replace them - but I'd not really linked the two things on the grounds that the brakes were not in use on either occasion so I assumed could not cause it - BUT Clyde's post has just reminded me that the car is sometimes self braking (like the handbrake is lightly on) when I stop on gentle slopes. That must mean the brakes are binding... in which case it starts to add up.

I'll jack it up in the morning and have a look at the other ideas.

>>trust its not a repeat of loose wheel nuts again.<< Well remember John! - although there was no noise this time.

Clyde - can you remind me of the name of that indie in Edinburgh you mentioned - I'll give him a go at sorting the disks&pad which need doing anyway.
Thanks
Mark

 

[clyde]

No probs Mark, he's Brian Miller at 2C Lanark Road. Tel 0131 443 7806

You may not be able to see anything wrong if it's the brakes binding on or at least I couldn't as they didn't seem bad when I jacked mine up when I was having the problem. Presumably it was the same for the OPC when they looked at it. I think normally they moved back enough not to bind but once in a blue moon they didn't. Possibly due to the force exerted on the pedal? But if you take the big pad retaining spring off the pads should be a little bit loose in the calliper. If you've still got the pesky anti squeel shims they wont move much, however, if you grip the outside edge with pliers you should be able to move them to some degree fairly easily. I would suggest that if you've got rust on the inner face of the disk then there's a fair chance that jamming pads are your problem.

 

[Mark Elder]

I've jacked it up and had a look around and pulled stuff about and it all seems rock solid steering wise at least.

The offside wheel is pretty rough as you manually turn it - in comparison to nearside. Anyway have now booked it in for a whole load of things to be done next week including replacing front disks and calliper clean out and possibly implementing the suggested grinding of the backing plate - but unless the callipers are well corroded themselves I hope this won't been needed with new pads going on.

I'm also going to get three "heating fault codes" sorted (showing up from my Durametric tester) - various flaps and motors not working. Was fine when I tested last autumn, then in March two faults, now 3! - I blame the bad winter.

 

[zrcg1]

I'd go with the pad/disc corrosion too, this happened to me more times than I care to mention in the past, but strangely not on my current set of discs/pads.

Doesnt help if your leave the car outside (in the wet) for a number of days without driving. The imprint edges of the pad left by the dry area (under the caliper/pad) leaves a rust outline which seems to create a heat build up when the pad rubs over it until its cleaned off. Never happened to me on any car but this one.

More than once i've pulled over on the hard shoulder checking each corner - it happened roughly the same time into each journey and was cured by stopping or reducing my speed to a slow crawl for a while. Put it down to the fact the pads started to bind then cool or release themselves at standstill.

Leaves a darky blue residue on the discs too, so you should be able to see something if its this causing it.

Out of the ordinary, but most issues I've had with my 993 are outside the norm.

Chris

 

[John Maddox]

I had this and I agree with comments re backing plates on front. I checked mine and found the pads were failing to move properly. I carefully sprayed wd40 behind the caliper plate and used an old feeler gauge to remove the corrosion. It took some time to do carefully but it worked a treat and braking and wheel wobble has been fine for last two years.

 

[Mark Elder]

ORIGINAL: zrcg1



Leaves a darky blue residue on the discs too, so you should be able to see something if its this causing it.

Oh - I get that all the time - been wondering why my disks look blue when others' are a clean silver colour!
Anyway - the disks need to go and I've known that since the winter...

 

[Pete B]

I've had exactly the same happen to me. Just the once - that was enough!
The car had been serviced only weeks before and the techie said that the brakes needed a good stomping on to clear the surface rust and the mark of the pads which had imprinted themselves on both front disks. I took the car for a longish drive and used every opportunity to stand on the middle pedal when the coast was clear. After about 15-20 neck wrenching stops I decided to drive home on the scenic route which involved a nice quiet stretch of newly surfaced dual carriageway. Halfway down the slip road the steering wheel nearly wrenched itself from my hands and the front of the car started to shake violently. Touching the brakes made no difference and after about 300 yards it disappeared never to return. The disks were certainly clean! I rang the garage and they reckoned it was a local deposit of disk pad material which had temporarily attached itself to the disk.........