xpl0sive

So I bought this 2007 S550 with 130k miles on it, noticed it had some noise in the front when I bought it.

Figured it probably needed brakes. Put new pads and rotors on it. Nothing changed. Then I figured it was the wheel bearings. Changed the bearings in both front hubs. Nothing changed.

It's making a loud metal on metal grinding noise whenever the wheel is turned left. Only does it when driving. Cannot replicate the noise when the wheel is off the ground. I've posted a video on youtube, maybe you guys can have a listen and tell me what you think it is. I'm at a loss here. It's not the dust shield, the wheel doesn't seem to be rubbing on anything....

Mike5215

Not a mechanic by any stretch but it sounds to me like it's in the steering rack/pump. Let's see what ALX thinks. Once in a great while I guess correctly and I feel like a big shot for a couple of days.

superpop

If it is 4matic it could be CV joints.

xpl0sive

not 4matic, just RWD. I took apart everything on the front end and could not see any places where there was evidence of metal to metal contact.

Mike5215

If you go fully left steering lock while the car is parked will it squeal like that or no?

xpl0sive

no it only does it when the wheel is turning. It's not the power steering pump or the rack. It's coming from the wheel area, doesn't have to be turned at full lock, starts doing it as soon as the wheel isn't rolling straight

superpop

try doing that same test but shut the motor off on the turn. Could be something rubbing only while the engine is running and wheel is turning. Also, put light pressure on the brakes to make sure it is not a hung caliper or rotor issue. Are you sure the bearings were properly installed?

xpl0sive

Tried applying the brake while turning, still grinds the same. Tried Lifting the car up, turning the steering wheel and spinning the wheel/tire by hand with the engine on or off. Does not grind. Bearings are fine, I think if they weren't, it would grind whether or not the wheel was on the ground.

superpop

Maybe suspension bushings? If they are work through you could get some grinding. Also, a bearing can grind under load and sound quiet when up on a jack.

xpl0sive

ya the only thing i haven't checked were the control arm bushings. I just can't understand where it would grind, since it only happens as the wheel turns. As far as the bearings go, the noise is exactly the same as before replacing the bearings, which leads me to believe that the old bearings were just fine and the new ones didn't make any difference

604benz

I see you are in the Vancouver, BC area, my independent shop is Henneken Auto he deals with only German cars, I would get him to check it out for you, ask for Hans, he's not cheap but his work is better than dealership quality

alx

Remove serpentine belt and try again. This will rule out accessory (ps pump). It sounds like dust shield is touching the rotor somewhere. Remove dust shields and try again. Also check pads if they are not stuck crooked...

xpl0sive

ya the only thing I haven't tried is removing the dust shield completely. I will try that tonight

xpl0sive

Took everything back apart. Can't see any evidence of metal to metal contact anywhere. Put everything back together, made sure all is correct. Grinding still there. Gonna get another set of rotors tomorrow and try that. I swear it's coming from the brakes.

DaveW68

You might be onto something here. It could possibly be the brake wear indicator. With the turning of the wheel, there may be just enough camber to hit the indicator, especially if the pads are worn down.

alx

Before replacing rotors spray them liberally with some brake cleaner and see if it makes a difference (sound gets better or worse).

xpl0sive

tried that already. when I had everything taken apart I cleaned everything with brake clean before putting it back together. The only thing I can think of is that the rotor is warped and making inconsistent contact with the pad. The only thing is that the sound stays even when the brakes are applied...

alx

i would try new pads first before new rotors.

also enlist a helper and when you circle the cul del sac have him/ her stay outside close to the car and listen where the sound comes from. you might just have the source wrong.

one more thing- does it do it when you go in reverse?

xpl0sive

- I already installed new pads. Nothing changed. I actually had new rotors on hand, but when I looked at the ones that were on there, they looked fine to me, so I just put the new pads on.
- I have asked someone to listen and they confirmed the noise is coming from the front wheel.
- It does make the same noise in reverse.

xpl0sive

Well it's not the rotors. Now I'm literally out of ideas. I'm getting tired of throwing parts at it. Only thing I haven't changed is the caliper. Could that be the issue?

superpop

Doubtful, if it is there regardless of brake usage then it is probably not a brake issue at this point. That only leaves, bearings, rack, suspension, has to be one of those if it is coming from the wheel area. I would start looking at the rack and how it relates to the motor pulleys, if the rack or pulleys are out of whack that would explain the behavior.

Mike5215

I said rack first if there's any sort of prize involved.

alx

How is your power steering fluid? Brake fluid?

As a last resort I would remove the caliper and hang it on a wire behind the wheel so it doest interfere (with something solid between the pads). If your pins are stuck pads might drag just the right amount to whistle.

Also, does it do it if you push a bit the emergency brake? Humor me... Maybe it comes from the back and you have tunel hearing

A long shot also is a dried up wheel bearing. They have no play, but will whistle when pushed hard.

If not any of the above- I say just drop it at dealer and have them run some chassis ears to pinpoint problem. At his point 1-2 hours of troubleshooting is well worth your money and sanity.

xpl0sive

power steering fluid is fine. the power steering pump is a bit loud, probably needs to be replaced at some point.
I don't see how the rack/suspension would make that noise. The noise only happens when the wheel turns. that would lead me to believe it has something to do with a part that rotates. There are only 3 parts that move... the wheel, the rotor and the hub.
The wheel isn't rubbing on anything, the rotors and pads are brand new and i just replaced the bearings in both hubs and packed them full of brand new grease....
I think I'm gonna take it to a shop and put it on a lift. I simply can't see the whole picture underneath the car while it's up on jack stands...

superpop

When you turn the wheel a lot of things move including the steering rack, if that rack is near a moving part and either are out of whack, that can cause the noise you describe. Jacked up you may not see the conflict but with the suspension compressed with the weight of the car the geometry could change enough that something is rubbing when you turn. If the noise is isolated to one event, IE when you turn, you have to look at everything that could cause the noise based on that event.