While in stop and go traffic the other day I noticed by 2001 volvo S40 was producing a pretty loud Knocking coming from the front driver side. As i sped up (over like10mph) it seemed to go away. However, after listening for it, it is present at higher speeds, and it is faster as the wheel turns faster, but while coasting only. The sound seems to go away, or at least be softer while braking or accelerating. Having just replaced my front struts, mounts, and sway bar links i know its not either of those, and just took the wheel off to look for anything loose. Didn't find anything. With the wheel up, I tried rotating the wheel to see if i could reproduce. I didn't notice it just by rotating, but if I quickly turned it back and forth, it sounded like I got a solid metal on metal knock. Is that normal?
What would you all suggest to check out?

 

My first guess would by a CV joint. At low speeds like in a parking lot and making a sharp turn do you hear the knock? Most CV joint failures become more noticable when making a sharp turn, but I have had one that knocked when going straight... that was on an old VW bug but the CV joint was pretty much the same as modern ones.

Other than that I know you said you had just replaced alot of suspension parts... did you do the work yourself? The parts might be good but maybe something wasn't tightened down enough.

Also about the knock, is it just a random knock, or does it seem to knock once with every revolution of the wheel?

 

Is the sound down low, like in front of your feet? If so you describe the sway bar mounts. Not the end links that connect the sway bar to the control arm, but the mounts that connect the sway bar to the frame. If you take off the wheel and get a strong light just follow the sway bar as it goes under the body and above the engine frame. The sway bar hitting the frame is where the noise comes from every time you run over a bump.

If it's not the sway bar mounts then consider the motor mounts. The main suspects are the bottom two mounts. You should be able to see if the rubber has cracked enough to cause noise in this case. I've not heard of the trans mount failing before but anything is possible.

 

To answer your questions, I did replace the suspension myself. struts and mounts. So that was my first thought too, maybe something came loose after the work, but I completed the job over 2 months ago, and just started hearing the noise in the past week. So, I went in and checked tightness on everything I touched. It was all still good.

Then knock itself might be with every rotation, and seeing as how it seemed to speed up with wheel revolutions, might be with every rotation? I had someone slowly roll the car down the driveway while I listened. It was definitely coming from or behind the wheel, but I couldn't pinpoint anymore than that.

I'll check the mounts, but the sound is occurring on good flat roads, driving straight. It doesn't seem to be caused by hitting bumps. I wouldn't think motor mount noise would increase with speed?

Of course, I didn't hear it on my commute this morning after taking the wheel off and looking around this morning. Figures.

 

Lug nuts? That was what my knock was. I'd tightened them with a torque wrench, too...

 

Varies with speed makes me think either wheel bearing or CV joint. Wheel bearings tend to make a grinding noise that slowly gets louder over time. It will also cause heat that will transfer to the wheel when it's really bad.

Every bad CV joint I've had made a clicking noise as opposed to grinding. I've read of others having a vibration with a bad CV joint. This one is a bit tough to diagnose without taking the joint apart or replacing it with another.

 

I inspected the boots on the CV boots and they were still good. Could the joints still be bad under unbroken boots? Its definitely not the grinding sound from a hub, its a solid knock/click/clak. Tried tight slow turns in a parking lot tonight too, no luck in reproducing.

I thought the lug nuts might have been it too. Especially since I didn't hear it today after tightening them. Would be weird though that they weren't making noise until now, 2 months after being touched last? And they weren't when I took them off today either...

 

Mine didn't start right away either...

Suspension Knocking Noise?

 

just today actually we put a brand new hub assembly on the passenger side front of my s80 t6. the noises that you are explaining are exactly what i had been dealing with, right down to the intensity at different speeds and such. we have a lift and heated garage with every tool under the sun so it took an hour and ten munutes from pulling it into garage to pulling out. not bad. give it a try, but hurry because the more you drive it you may actually damage brakes as the bearing wears.... let us know how u make out

 

The knocking hasn't come back since I tightened up the lug nuts, so probably was just that. Thats everyone.