slalom noise
 

I've been having this weird "thump" coming from the front end for a while now. When I go about 30 mph and steer left to right as if I were doing a slalom I can feel and hear this light "thump" sound and I can feel it through the floor and gas pedal only. Can't feel anything through the steering.

It's not the battery or spare tire being loose, I checked those and crossed them out. Frunk is empty. I took the car to a suspension shop while I was getting an alignment and had them check and they can't figure it out either. There doesnt seem to be excessive play in the front wheels.

What in the world could it be? Wheel bearings? I have no noise from them at all but according to maintenance records they are original at 135K miles.

2000 2.7L Manual, ROW M030 suspension, original lower control arms, drop links changed 25k miles ago. The steering is still pretty tight.

Anybody has any ideas?

Thanks,

Cristian

You put the car in the air and wiggled the tires I trust.

How about motor and transmission mounts. All original. I know in the rear but sometimes the chassis transmits things and fools us.

Thanks for the answer mike!
I put a new engine and transmission mounts myself a while back so I'm good there. Just put new tires on the front and got an alignment and with the wheels in the air we checked and there was no significant play.

I recently replaced the suspension with the M030 kit and basically went through quite a bit of the front and rear components and me and my mechanic didn't notice anything out of the ordinary. I had the same issue before the swap as well so I'm counting out springs shocks and sway bars.

It does it in gear or in neutral steering both left and right

Spare or tool bag floating around in frunk?

This doesn't sound like a wheel bearing to me. Failing wheel bearings will often sound like a constant "rumbling" noise during either a right or left turn (depending on which side wheel bearing is failing).

Even if both left and right wheel bearings started to fail at the exact same time (which would be pretty rare), you would hear the rumbling move from one side to the other as the car was driven in a slalom of repeated right and left turns.

A thump sound implies that something is moving and then hitting something else which stops the movement and its moving back and forth as the car slaloms. Often suspension and steering problems are only apparent under loads, so it can be hard to find the exact problem with the suspension and steering unloaded when its up on a lift.

Timco that was my first go to so I test drove without the spare and tool kit. Could still replicate the issue.

Thom that makes sense about the wheel bearings.

Could it be some ball joint or bushing that's not tight anymore? Coffin arms are original so are the tie rods and everything on the steering rack.

Again I did check these things to the extent of my ability but as you said this only shows under high load like very hard steering, I can't feel a thing under normal driving conditions.

Honestly if I can't find the culprit I'm gonna let it be and see if it gets worse and maybe easier to diagnose. because it's such a minor nuisance I'm not going to throw parts at it.

Any ideas are welcome guys!

Thanks again,

Cristian

you might check the lower control arms. when the bushing goes bad, it starts as a thump you can hear and feel. I first noticed mine only during cornering, then on a bumpy road. It also started as only an occasional noise, then got progressively worse. If the rubber boot around the bushing is intact, some posters have been able to inject grease through the boot and have the noise go away for several months.

Excellent tip thank you! I'll check the bushings and report back.

If I do end up replacing front control arms do I need an alignment?

Binding front sway bar bushings? If you are OEM though I think.they have the fabric type of threads in the bushing which don't require any lubrication. If they got grabby, or loose and worn out, that bar could thump around a little. To check you could lift the car and pull it but it might only happen under heavy twisting (like a slalom) but you might be able to inspect the bushing with a flashlight.

If you have adjustable drop links, the bar might be hitting the lca under full compression (a stretch, I haven't really looked at the front lately)

No alignment needed when replacing LCA with like OEM parts.

I replaced the sway bar a while back when I put the M030 kit on and bushings were virtually new so that might be a long shot but while I'll have the car up I'll check those out too.

Thanks for the input Steve!

There are LOTS of moving parts up front and many will be hard to diagnose

http://image.superstreetonline.com/f...suspension.jpg

Shock top bearings??

Control arms and coffin arms would be the most suspect I think.

Don't think it's the shock top bearings because they are almost new and I had the same issue before replacing them.

So far control arms are the prime suspect.

Is there any sure way to check if they are cracked? I think I can take the to a place with a lift where the wheels are not in the air, that would be the best way right? If the wheels are in the air then what's a good way to check? I hear sticking a pry bar between the coffin arm and checking the bushing for cracks? Are any cracks/tears allowed at all meaning could they be just superficial or if see any they are done for?

It's prob about time I replace them since they are original but i only want to buy parts if I really need to.

Why don't you borrow a GoPro camera and mount it under the car or in the wheel well and take it for bumpy ride and see what you record. Perhaps you can capture the sound and at least examine the parts as they are stressed?

With 135K on the car, I'd say it's the control arms. My 2002 with 145K made similar noises, and after I rebuilt the suspension, all is now quiet and thump-free.

If you are going to have it apart enough tot replace the LCA's, you may as well replace everything else, too. Expensive, but the results will be worth it.

That's a good idea! If I can't pinpoint the issue I might resort to that, I have a gopro. It will at least make for an interesting video if nothing else :)

I'm getting there in terms of refreshing the suspension :)
LCA and tie rods are about the only original parts on the car.

Tomorrow I'm going to replace my O2 sensors and while I have the car on the lift I'll have a good poke around and see if I can confirm the LCAs are bad. I'll report back.

Thanks to all for the input!

Cheers,

Cristian

Well.. I think I had one of those "Now there's your problem.." moments when I checked my LCAs.

http://i1314.photobucket.com/albums/...pskimezq1e.jpg

http://i1314.photobucket.com/albums/...psygfyypu0.jpg

Looks like one is quite torn. I didnt take a photo of the other side but that one also showed signs of surface cracks and is probably not far behind.

I was only able to see this with the car up in the air and the suspension preloaded.

I'm getting some new LCA's to replace and will report back with the result. Hopefully this is the only culprit as I couldnt notice any play with any other parts while checking.


Thanks to all for your great feedback!

Cheers,

Cristian

Glad that you finally found it!

If you have the money, I'd replace more than just the LCA's.

Ha! That is toast...

R&R is quite easy and you get new ball joints too!!

Have fun.

What else should I be replacing?
I do have fairly new shocks and springs, sway bars and drop links.
I checked the tie rods and no play there.

I think I'm pretty covered right?

Other than the parts you list, the front caster control arm (the front axle equivalent of the trailing arm or track arm from the back that often makes noise) has a bushing that can wear out.

The 986 part number is hard to find outside of cheaper parts of indeterminate origin, but the 997 rear trailing arm is an exact match for the 986 front arms, the part number is 99733104301. I'm running these on my car right now, both Meyle and TRW make this part.

However this can be replaced without having to take off the front LCA so you can always do it later. And to remove the old LCA you will have to take off the fork end of that arm, so at that time you can move it around and see if it rattles or moves around outside of the intended range of motion.

Here is a video that supposedly shows how to test the ball joint in these types of arms to see if they are bad:

MAINTENANCE - Porsche 996

neat trick there for checking those parts! thanks Steve!

mine dont make noise so I'll skip on these for now and check them when I work on the LCA.

I do have a question about not needing to do an alignment after swapping LCAs. considering one is torn I imagine with the weight of the car it's sitting a bit off due to the bushing. with new LCAs and new "straight" bushings wouldnt the caster be a bit off? or is that difference negligible?

Caster is not adjustable and (in my opinion) the camber is only very slightly affected if that center bushing is worn. Of course, if the center bushing is worn/torn. the rubber bushing on the inboard end of the LCA might also be worn out as well, maybe after you put it on you can get a free alignment check at a place that does those?

thanks Steve!

the bushing is bad but it's not completely torn so I'll probably not need adjustment. I will also check the inboard bushing on the LCA. If I'll be in the neighborhood I might stop by the alignment place to double check further down the road.

thanks for the new LCAs you're sending my way! ;)
glad I could take those off your hands.

New lower control arms ('coffin arms' as some refer to) will renew your cracked "track arm coupling" bushings shown as presently being cracked, your ball joints, and the inner rubber bushings as well, which is where camber is typically adjusted via an eccentric mounting bolt.

Even if you mark and line up the eccentric bolts in exactly the same positions as they were before, you will *definitely* want to re-align the car afterward.

Jake I believe that's for the rear where the camber is adjusted through that bolt. The ones I'm replacing are in the front where the camber is adjusted through the top of the shocks (the little adjustment it allows) so camber wouldn't be affected.

Even if non-adjustable, I'll bet those a-arm to frame bolts will have some slop. The rubber bushings being replaced may have taken on a set, the manufacturing tolerances of the replacement arms will never be completely consistent, resulting in dimensions being slightly off from the old ones. Any changes in effective control arm length will be amplified by potentially severe, tire-eating toe-in/toe-out angle changes, which is the main concern if you have decent tires that you care about making last. If you want to check just one thing, I'd check toe. If you don't care much about tire wear, of course, your call to forego the alignment.

I got a "lifetime" alignment for my p-car, because I expect to do a bit more suspension work going forward. I was shocked at how far off the alignment was even after trying to put things back together as they came off. Although, I suppose it's possible that YMMV. I seem to recall you've already done some suspension work, so you know the drill. Nice job tracking down the torn bushing, by the way! Good luck. :)

I see what you're saying and I JUST put on a fresh set of Hankook RS4 that I'm trying to make last so I'll most likely swing by the alignment place(for the 4th time this year :D).


This is what happened to my front RS3s with about 10k miles on them.

http://i1314.photobucket.com/albums/...ps1sc9ssbs.jpg

http://i1314.photobucket.com/albums/...psoevkizl5.jpg


They still had tread on them:

http://i1314.photobucket.com/albums/...pszlw5tuzd.jpg


I made a claim with tirerack and they passed it on to the manufacturer who calls it "ozone weather cracking" so they will reimburse me for part of the price based on the tread left. Still waiting to see how much, they came and picked up the old tires.

The tires were on the car for 8 months maybe. Driven hard and autocrossed a few times. I guess these softer compound tires dont do too well with lots of heat cycles. Good thing i spotted the cracks and will be getting some $$ back. :cool:

well.. they just reimbursed me half of what I paid for the two front tires which is pretty good considering the tires were worn especially on the inside since I had -1.5 degrees of camber.

thanks "ozone weather cracking"! :dance:

props to Tire Rack! they run a pretty tight ship!

I got around to installing the new front lower control arms in under 2 hours and happy as a bunny, patting myself on the back I went for a test drive and it still makes that slight thump.. As I was replacing the LCA's I also checked the front trailing arms and they are in good shape.

well.. I'm fresh out of ideas.. :confused:
I was almost sure that's what was causing it.

what else could be in the front that's making that causing it? could it be something else but the suspenion? like something that sits in front of the firewall around the battery, brake booster, etc and is loose?

thanks guys!

Cristian

i figure i'd update this thread.

it was the stupid spare tire causing the thumping!!!!!!!!!!!!!! :)

i know i initially thought it wasnt but i tested again with the spare tire out and no more thumping. talk about chasing ghost issues.. :D

trouble is no matter how hard i tighten the spare tire it still moves around. why doe it even have this cut where the bolt sits allowing it to move left and right? it doesnt bother me now that i know there's nothing serious but i am curious if i am maybe missing a piece or something to really make it stay in place during hard turns?