low hum when turning left...

john baldwin · john baldwin's Garage

...low hum from left rear only in left turns and starts as the steering wheel moves just off center. Sound increases with decreasing radius as the G's increase. Wheel bearing? CV joint? Jacking up car and pressing in on top and bottom of wheel shows no movement. Any thoughts on how to diagnose appreciated.

Jesse16 · Jesse16's Garage

Sounds like wheel bearing noise to me. Seems thats just how guys at my shop described it would be when it happens. I think rear CV noise would be more difficult to hear unless there all the time. Unfortunately two bearings, very close to one another.

twistoffat · 06-07-2011, 05:57 AM

I´d say its the bearing too. The 12 O´Clock 6 O´Clock trick doesn´t always identify it

jmohn · jmohn's Garage

That was how mine began, it got progressively louder over time, until I finally diagnosed it as probably a bad wheel bearing. Which it was. Replaced both rear wheel bearings, all is now well. BTW, there was no lateral movement on my wheels either.

Jerry M
'78 SC

hcoles · 06-07-2011, 07:05 AM

The other day we used a long wood axe handle (a 1" wood dowel or similar would be better) pressed on the arm near the bearing and held against an ear, comparing car with suspected RWB noise and another 3.2 with known good bearings, you could definitely hear the difference, could also hear the difference by rotating the wheel jacked up. There are a number of threads here on how to pull the bearings out, a puller can be made from parts purchased from OSH. If you are not careful while installing the new bearings in you might be doing it over again soon. Be careful how you use a hammer if used at all. I pulled my bearings in, but you don't have to if you can apply force only on the outer race.

mikehinton · mikehinton's Garage

Mine did the same thing, and it was the bearing. Honestly I couldn't really detect the problem by trying to rock the car back and forth. If it's not making much noise, you'll have time to attend to it before it becomes critical.

FIG · FIG's Garage

Quite a few threads here on replacing the wheel bearings (bastard of a job I might add!).

Thanks to Pelican, the job got done and the noise of the engine is the only thing I hear now!

john baldwin · john baldwin's Garage

...the guy I use when I'm stumped (he did the PPI too). He put it on the lift, (I gotta get one) while his assistant climbed up, started the car and ran it up in second gear then idle, while he took his stethoscope and listened to both bearings...pronounced both OK, but thought the right rear might be worse than the left (?) We took it for a spin, and while he could hear the groan, didn't think it was so severe as to warrant replacement. "Enjoy the summer", keep driving it, replace them next year (winter). No charge. OK then! (I've read all the threads on DIY replacement and am ready with bearings bought, but would rather see her on stands off-season rather than now!)
Thanks for all your inputs!

FIG · FIG's Garage

Does it 'groan' whilst straight line driving, under load etc other than cornering?

I found my CV's were very 'pitted' and caused a groaning noise whilst normal driving without turning. Changed them, noise gone!

Changing both bearings should take you about a weekend, changing bearings and 4x CV's not that much longer, so no real need to wait till winter if the noise is anoying you that much.

You will need a few tools (as well as some that you will have to make if you dont have the Porsche tools) and as per the threads you have already read, you will need patience and a few beers! Oh and BTW hide the swearing jar... you'll be broke!

john baldwin · john baldwin's Garage

FIG,
Thanks for your input, however I'm still not sure I want to tie up three weekends under the car...(projects always take me triple the time!)... I'd rather be sailing...New England summers are short enough!
No noticeable groan going straight...only the left turns.
Any particular tools I need to buy?..thought those DIY tools listed in these threads pretty much summed it up.

DRACO A5OG · DRACO A5OG's Garage

Ball Joint Remover ( not pickle fork but the screw press type at HB )
Spanner Wrench ( but a short socket will work to remove strut nut, just take care and watch the fender )
Punch Tool ( or piece of steel, just leave nut on end of joint bolt flush the use a Sledge )
Penetrating Oil
Torque Wrench
Ball Joint Socket & Impact Wrench ( Pipe Wrench with cheater bar will work just as well )
Brake Fluid ( you will need to disconnect the brake line, place a 24" blokc of 2X4 and depress the brake to prevent fluid leak, then bleed when done )

Most tools can be rented for FREE at a FLAPS

Take care when removing the strut, DO NOT LET IT HIT THE UNDERSIDE

Beer ( Nice reward at the end )

Jim

FIG · FIG's Garage

I also used a slide hammer which was great, along with gear pullers (for the remaining bearing piece).

Not for the faint of heart, but rewarding none-the-less. Take your time and TRY to enjoy the ride.

john baldwin · john baldwin's Garage

Thanks, Guys. I keep this thread bookmarked and go through the tool list when I revisit the procedure. I'll post my experiences when I tackle this.
Cheers!

john baldwin · john baldwin's Garage

hum still there...would like to address it the simplest way possible (obviously). Searching other threads reveals tires as a possibility (old Dunlop 8000's)...Left rear worn to the wear indicators (but why would this cause hum in left turns only?) or cracked sway bar mounts (PO had originals replaced)...not sure how to inspect these or what to look for?
Any thoughts appreciated as always.

twistoffat · 06-10-2011, 04:00 AM

If only the left rear is worn it could indicate an alignment issue. This could also explain why then the noise appears on left turns. Sounds like you are due a new set of rear tires. Get that done and realinged and see what happens to the noise

hcoles · 06-10-2011, 09:08 AM

good point, IME tires can make all sorts of strange noises sounding like bearings going bad/etc. you might try borrowing tires for a few minutes, if another Pelican or other with tires that fit and see if the noise changes

john baldwin · john baldwin's Garage

Thanks guys. Not sure I can find local Pelicanite to loan me tires but I do need to get on with replacing at least the rears. However I first need to roll or trim the front wheel lips and lower it. My dilemma is whetherr to increase the wheel dia to 17" with existing BBS centers (see garage pics), swap to Rotos or just leave it alone...I know there's more than one right answer but opinions are welcome!