tedrich

I have a '90 C4 cabriolet with 97K miles. I am getting vibration and howling from what seams to be the left rear wheel. I also hear an additional thump when corning to the right. I found a bad CV joint and replaced both rear half shafts with maybe a small improvement. I have jacked up all four tires and tried shaking them to see if I could feel any play, I do not. Is there a better way to determine if a bearing is bad? Also, the repair manual I have directs me to heat the suspension arm to install a new bearing. Is this necessary, or can I press the new bearing into a cold arm. Could there be another reason for the vibration?

Thanks,
Ted

Adrian

Dear Ted,
The howling is certainly the indication of a failed wheel bearing. The thump could actually be the wheel hitting something. I really do not recommend you keep driving because you may damage your hubs and your rear park brake assembly which sits inside those hubs. Having to replace your rotors gets expensive.
I would also look at the rear shocks.
Ciao,
Adrian
964C4

PS: I have never changed rear wheel bearings. I think Jeff Curtiss has and his expertise should be listened to in these areas. He is really hands on.

Jeff Curtis

A wheel bearing it very well may be...but I would check the "easy" things first.

First of all, make sure your rotors aren't warped, or the dust shield is not bent and actually rubbing against your rotor under side load. (while turning)

The CV joints/axles would be the 2nd place to look, especially if you have a "clunk" every now and then.

...but you've already addressed that issue.

I remember the only time I dropped an axle on my C2, pulling away from an ATM, with my high-spirited Nephew in tow (he was going to lunch w/me and then down to the track in Iowa when I was visiting, Summer of 2002) - I heard a few clicks, pondered WTF and went on...about 20yeard later - CLUNK!!

Eeeeeew, I hate to think of how that ruined our day...as my rig and ALL my tools were at the friggin' track!!

Anyway, sorry for the sidebar.

As for wheel bearings clunking, hmmmmm, I guess it's possible, but that would mean that they are VERY loose in the trailing arm and moving around...in that case, buy a new trailing arm too! ...you'll need it.

The bearings have to be pulled out via a nifty expensive tool from Porsche...and you can use the same assembly to press them back in. This is not a job for the faint of heart as it involves pulling all kinds of goodies apart.

If you're not into that, consult your local P-Car technician...it's about $110 for the bearing and $300 labor per side?? ...something like that.

I did mine, it was fun, no major issues. I thought one was going out, still not sure if that was it, but rolling down the highway is a bit smoother now.

I had pics all ready for Adrian's book, but cannot recall if I sent them in or not. Do a search for my post regarding wheel bearing replacement to get an idea of when I did them...think it was last May??

Anyway, I have pics if you want to see a couple - I'm just a PM away.

Phil Raby

The special tool isn't strictly necessary. If you heat the arm around the bearing you can drift it out from the inside. I wouldn't call the job fun, though

Oh, and go to a bearing supplier for the bearing, not a Porsche dealer - it'll be half the price.

Cheers

Jeff Curtis

I agree Phil, the bearing can be had at a MUCH better price...I found that out later.

As for heating up the trailing arm, etc. - while that's not exactly suggested, it would work fine...it's the act of heating it up that disturbs me.

Adrian

Dear Jeff,
No, you never did send them,
Ciao,
Adrian
964C4

PS: Sadly it would not have been possible to use them unless we had the procedure verified. I learned a lot about such things with the first book.

Phil Raby

You don't have to get it that hot. We're not talking molten aluminium here

tedrich

I shook and prodded every bit of the suspension and could not find anything that was loose, so I took the car to a trusted mechanic and after listening to it he decided that I indeed has a bad left rear wheel bearing. He replaced the bearing, as well as pads and rotors, and now all is well with my Porsche.

Thanks to all that replied.
Ted

Adrian

Dear Ted,
Thanks for the feedback.
Ciao,
Adrian
964C4