Steering wheel shake while braking

[xxaarraa]

Hey guys,

03 C4S. 32k miles. PSS10. Driving to work today, there was a loud clunking noise as I was merging on to the highway - felt like something fell off the front of the car, but banged and clanged its way through to the back. I looked in the mirror and coudn't spot any pieces flying around but my first instinct was I either picked up a big rock or something came loose and rattled its way back. Car drove fine so I kept going.

• [*]I get to work and notice that as I brake from 20-25 mph, the steering wheel shakes badly.[*]As I go over bumps, there is a rattling noise.[*]When I brake hard from 10-12 mph, there is a clunking noise and feels like something is loose. Best way to describe is that it feels like ABS is kicking in.

What I have managed to isolate so far:

• [*]There is no pulsing on the brake pedal (I thought it might be rotors)[*]Braking at speed seems OK. [*]I looked over the paperwork from the previous owner and the PSS10s were done less than 2000 miles ago and they did strut mount bearings as part of the job. [*]Cannot find anything in the previous paperwork to indicate rotors or pads were ever done. Currently at 31,600 miles.

Any tips on how to go about checking this stuff from easy to hard? Cross drilled rotors cannot be turned correct? Usually, I'd just say heck with it and do rotors and pads, but the clunking I heard today makes me hesitate.

Thanks a lot for your thoughts,

Edited April 17, 2013 by xxaarraa

[mghorayeb]

Get it on a lift ASAP, take the front wheels off, and take a close look at all components. No sense in speculating.

...and while you're down there see if there's any residual damage along the bottom of the car.

We're with you, Boston.

Edited April 18, 2013 by mghorayeb

[JFP in PA]

I agree 100%, get the car up in the air, pull the front wheels and start looking. I also would not be driving the car until it is inspected.

[xxaarraa]

Guys, thanks but thats exactly my intention also. I am asking if anyone has tips on what to check inspect that might be a common wear item on these cars. "take it to a shop" is easy, but looking for more insight.

[logray]

If you have clunking and rattling noises I have a feeling it is going to be apparent when you are inspecting it.

[JFP in PA]

Guys, thanks but thats exactly my intention also. I am asking if anyone has tips on what to check inspect that might be a common wear item on these cars. "take it to a shop" is easy, but looking for more insight.

You need to start looking at the entire front suspension and steering, giving things a good shake as you go. If something fell off, and now the steering wheel is shaking, I cannot imagine looking at the car and not seeing anything wrong........

[xxaarraa]

Taking it down the street to put it up on a lift tomorrow. Will keep you guys posted on what I find.

[xxaarraa]

Alright guys, had it up on a lift and found the problem within 30 seconds. Quite scary. Ready for this?

BOTH my front A-arm (or trailing arm I guess) bolts are missing. Its the bolts that hold the front of the arm to the subframe. Gone. We were able to just wiggle the A-arm back and forth as it was held on by only the rear bolt.

I guess this is good news and bad news. Good news because we know what the problem is and it's an easy fix. Bad news because I want to know how the heck a critical bolt like that just vibrates off, especially the pair of them.

Car is parked at the shop as I didn't want to drive it. Going to call Porsche in the morning to see if they have the bolt in stock. Anyone know if they would or a specific part # I should be chasing down?

Edited April 18, 2013 by xxaarraa

[JFP in PA]

I thought it might be easy to spot. See if this helps ID the part you are looking for:

[xxaarraa]

I thought it might be easy to spot. See if this helps ID the part you are looking for:

Hey JFP, thanks man. Do you have the part #'s that correspond to this diagram? I called a porsche dealer on the west coast (past business hours in boston) and described the bolt. He said he thought it was part # 90037832901. Trying to cross-reference that against your diagram might help me isolate.

[JFP in PA]

Part # 90037832901 would be item #4 in the diagram.

Go to http://www.autoatlanta.com/ website, look up your model and you will find that diagram under the steering/front end section with the part numbers for each item. You can also find the same info if you have access to a Porsche PET. Good luck!

[xxaarraa]

Part # 90037832901 would be item #4 in the diagram.

Go to http://www.autoatlanta.com/ website, look up your model and you will find that diagram under the steering/front end section with the part numbers for each item. You can also find the same info if you have access to a Porsche PET. Good luck!

Thanks. Item # 4 does not look like the part. I think the bolt I am looking for is # 11. But I will print this out and take it to the car this morning and confirm.

FYI, I found these on Porsche.com also. http://www.porsche.com/all/media/pdf/originalparts/usa/996_USA_KATALOG.pdf

Edited April 19, 2013 by xxaarraa

[JFP in PA]

Part # 90037832901 would be item #4 in the diagram.

Go to http://www.autoatlanta.com/ website, look up your model and you will find that diagram under the steering/front end section with the part numbers for each item. You can also find the same info if you have access to a Porsche PET. Good luck!

Thanks. Item # 4 does not look like the part. I think the bolt I am looking for is # 11. But I will print this out and take it to the car this morning and confirm.

FYI, I found these on Porsche.com also. http://www.porsche.com/all/media/pdf/originalparts/usa/996_USA_KATALOG.pdf

That is an online copy of the PET, which is their parts catalog.

[xxaarraa]

It did turn out to be # 7. Special order from Porsche I have both on order. In the mean time I found a couple of M14x1.5x100 bolts at a local recycler. The #7 bolt I have on order are M14x1.5x110. I figured 10 mm shorter bolt should be ok for a few days to get me around till the Porsche bolts come in.

Assuming I'd need a full front end alignment once this is all done correct? Any special tools or machine needed or can the local shop get it aligned to factory spec?

[logray]

It wouldn't hurt to throw it on the alignment rack, but you could also just retorque those fasteners properly (I would guess they were improperly torqued), then test drive the car. If it tracks straight then I don't see why you would need to align it.

Any shop can align it and get it reasonably well, but I've found that shops who know Porsches can typically do a MUCH better job.

[xxaarraa]

Jfp, any chance you can lookup torque values for the #7 from your Bentley manual for me?

[JFP in PA]

It did turn out to be # 7. Special order from Porsche I have both on order. In the mean time I found a couple of M14x1.5x100 bolts at a local recycler. The #7 bolt I have on order are M14x1.5x110. I figured 10 mm shorter bolt should be ok for a few days to get me around till the Porsche bolts come in.Assuming I'd need a full front end alignment once this is all done correct? Any special tools or machine needed or can the local shop get it aligned to factory spec?

I would also suggest a front end alignment done by a competent Porsche shop. Considering what started all this, I would also get under the car with a torque wrench and check every non castellated nut for the correct torque specs.

[JFP in PA]

Jfp, any chance you can lookup torque values for the #7 from your Bentley manual for me?

#7 is a M14X160 bolt, spec is 118 ft. lb.

[xxaarraa]

Jfp, any chance you can lookup torque values for the #7 from your Bentley manual for me?

#7 is a M14X160 bolt, spec is 118 ft. lb.

Thanks JFP. I think you and I are looking at different fiches for some reason. Here is what I am looking at from Porsche's website and shows #7 as a M14x1.5x110.

[JFP in PA]

Jfp, any chance you can lookup torque values for the #7 from your Bentley manual for me?

#7 is a M14X160 bolt, spec is 118 ft. lb.

Thanks JFP. I think you and I are looking at different fiches for some reason. Here is what I am looking at from Porsche's website and shows #7 as a M14x1.5x110.

I was using the diagram in the Bentley manual; the PET should be more correct, although the bolt may also have been superseded, so I would stay with the PET. The torque spec (from the OEM service manual) is correct at 118 ft. lb.

[xxaarraa]

Thanks. The dealer did confirm that the part # for 7 was superceded by a different number: 90037832901 which is what I have on order. So who knows, Porsche might have superceded the 110 bolt with a longer 160 bolt precisely to avoid what happened to me!

[JFP in PA]

Thanks. The dealer did confirm that the part # for 7 was superceded by a different number: 90037832901 which is what I have on order. So who knows, Porsche might have superceded the 110 bolt with a longer 160 bolt precisely to avoid what happened to me!

Not an uncommon occurrence, Porsche is learning by experience, just as we are. I would suggest also getting a replacement for the same bolt on the other side of the car, bolts are relatively cheap, fishing the car out of ditch after the front end falls apart at speed is not.........

[xxaarraa]

Thanks. The dealer did confirm that the part # for 7 was superceded by a different number: 90037832901 which is what I have on order. So who knows, Porsche might have superceded the 110 bolt with a longer 160 bolt precisely to avoid what happened to me!

Not an uncommon occurrence, Porsche is learning by experience, just as we are. I would suggest also getting a replacement for the same bolt on the other side of the car, bolts are relatively cheap, fishing the car out of ditch after the front end falls apart at speed is not.........

hmm yeah, two bolts are on order - one for each side of the car. BOTH of them went missing!!

[JFP in PA]

Thanks. The dealer did confirm that the part # for 7 was superceded by a different number: 90037832901 which is what I have on order. So who knows, Porsche might have superceded the 110 bolt with a longer 160 bolt precisely to avoid what happened to me!

Not an uncommon occurrence, Porsche is learning by experience, just as we are. I would suggest also getting a replacement for the same bolt on the other side of the car, bolts are relatively cheap, fishing the car out of ditch after the front end falls apart at speed is not.........

hmm yeah, two bolts are on order - one for each side of the car. BOTH of them went missing!!

Just as an aside, who was the last to work on the front end of the car? You mentioned you have aftermarket suspension pieces..........

[xxaarraa]

I got the car about 500 miles ago from a private party. He was the one who put on the PSS10. He had all his work done at a reputable Porsche indy (sets up cup cars) in Framingham MA - IMS/RMS/AOS/clutch/suspension/strut mounts/etc.

All the paperwork I have for about $10k in repairs is from that shop, but I have no way to tell who did the work. It's hard to imagine they would take the A-arms off to do struts, but weird.

Edited April 19, 2013 by xxaarraa