Wheel Bearing?

Hello, after some advice (again!) Just taken the car out for a drive and noticed a light knocking through the steering at low-speed (can hear and feel it). Not getting any drone/noise at higher-speed. I put the car up on the lift and went over the front-end. I cant see any movement in any of the bushes etc. However I can get some movement (can see and hear it) in the front drivers-side wheel, if I grip the tyre at the top and bottom and push/pull it. Looking at the top of they tyre, it looks to be moving relative to the spring/strut (a tiny amount, 1mm or less). The noise seems to be coming from the hub area. In the past, working on other older cars, that usually means the wheel bearing is shot. However reading online, when other people have posted similar issues on forums, it has been have suggested that you wont identify a bearing issue in the 996 via this route and that tie-rod ends are a more likely culprit for the steering knock. Am debating do I go with my instinct and just do the bearing. Or do I go belt and braces and do the bearing and the track rod ends (will mean getting the alignment done...) Welcome any views. Cheers Ben

Slight play top and bottom movement on the wheel will probably be in the shock absorber but i would have a very close look at the bottom coffin arm ball joint .. you need a second person really to rock the wheel whilst you look . A wheel bearing cant make a knocking noise .. well if it does your in big trouble .. it will be a drone and similar to tyre noise .. it will be louder when cornering on one side .. far more than cornering the other side. I take it this isnt when brakeing but just low speed driveing . best test for the coffin arm ball joint is a lever bar between it and the hub with the wheel off the ground .. look for any movement .

I would not expect a knock from a wheel bearing unless it was totally shot, usually you get a whining noise that is loud when you corner in one direction and not in the other as the bearing load changes. I would have thought that knocking is more likely to come from a failed joint steering ball joints for example.

deMort, you beat me to it and with a better reply as usual. Excellent!

All that matters is that the OP gets some answers . We also come to the same conclusions and that always reinforces the idea . :thumb:

Both- thats brilliant. (DeMort am always amazed that you spend your working week on these cars and then give up your free time to help people fixing them!) Will get a pry-bar and test the ball joint on the coffin arm (the arms themselves look very new and the rubbers look in great condition).

Ive been haveing a think about this .. you can "feel" the knocking through the steering wheel .. thats a little unusual . Have a good pull up and down and outwards on the link rod that side .. thats more the sort of thing if you can feel it i think .

really appreciate all the help. I followed your advice and just went back out to the garage, I took the air-flow plastic (guess it directs cool air onto the disks) off the arm, so I could get a decent lever onto the lower ball-joint. There was no play at all....looking at the arm, I would guess its fairly new. So I followed your second tip and got someone else to help. With my wife rocking the wheel (12 o'clock and 6 o'clock) and me under the car, I could see and hear that in fact the movement is much higher up than I thought, its actually at the top-mount.........Sorry, I know I said it was coming from the hub, it sounded that way when I was beside the car, but underneath it was clear it was not coming from the coffin arm and there wasnt any movement there. Just googled top mount and knocking at low speed, there are millions of threads on it, looks like its a common issue. Now to work out what to do about it....

Top mount makes perfect sense .. just replace it .. its a bearing and a rubber mount .. you really need a geo after replacement but you can get away with just marking the nuts then useing that mark . If your good with spanners then its a home job .. if your not so good then ill suggest a garage .. there are a couple of bolts that might cause issues if your not used to this ... Hell there are a couple of bolts that have given me no end of grief in the past .. and i work in a fully equipped workshop ! EDIT .. Ill bet your wife loves you .. clean hands .. this time of night and wiggleing a wheel !! She has my sympathy .

Thanks DeMort - will have a go myself, whilst new to Porsches, have worked on plenty of cars (mainly older/simpler e.g. Minis and Mk2 Escorts). Just read a few guides and looks ok. You correctly guessed that my wife was 'delighted' to help, especially as I came in asking for help just at the point she was trying to sit-down having put the kids to bed. Then to add to her misery both kids re-appeared, with various well-trodden excuses for being back out of bed.....

Sorry, silly question. Do I need to do both top-mounts, even though I only have an issue on one side?

Yes it would be daft not to do both. I had a saga with top mounts, bought the cheap ones from design 911 and they failed soon after. Remove the plastic trim above the top mount. Remove the plastic circles. Get in your frunk and bounce up and down (seriously) whlst holding your finger on the big nut. You will feel it knocking. Your neighbours will think you are crazy You may need a buzz gun impact wrench to get the big bolt off. Some people use mole grips at the very top of the damper shaft wrapped in tape to stop it rotating. You can remove the cup washer and see the rubber top mount, see if its separated. On a C2 you can get top mounts out without removing the struts (the ARB bolt securing the damper will be stuck). Jack the front up. Use spring compressors to ....er.... compress the spring lots. remove the 3x top mount bolts. Push down hard (you are fighting the dampers) on the top of the shaft. The damper will try to slowly rise Quickly pivot the strut out of the wheel arch before it rises..... Swap the top mount. I think I also removed the brake caliper to do this so not to stress the line. Maybe I also loosened the coffin arm bolt too to as not to stress the rubber bush.

Use the SACHS brand top mounts from autodoc.co.uk £20 each. Mine came with Porsche part number ground off...they are the same as you would get at the OPC. You may also need the ball bearing from your OPC only. Oh, and you should get a geo check afterwards. I marked my 3x top mount bolts first to get them approx back in the same place. I also had a shock with play as Demort said. And inner track rods knocked only when hot. Everything in the supension was worn on my car over 110k miles.

Thats brilliant, really appreciate the write up, thanks Wasz. Will get the bits ordered ....I had found your other threads on the cheaper part - I will get them from the same supplier. I have a couple of cordless impact wrenches, so hoping the bigger (makita dtw450) will do it, its not failed me yet.

You dont have to do both sides but the way i look at it .. they are going to be the same age .. maybe do the bad side and see how you go and save the other side for a later date I love that the kids showed up .. they can sense when something is going on bless them .. well bless them if they goto sleep on time perhaps ! My sympathys to your poor wife