2001 S40 has a knocking noise, which I can feel in the pedals, when coasting. While accelerating, no knocking noise or feel, nor when braking. It's only when i'm coasting, going from accelerating to braking, there is a knocking noise and feel. It's really prominent in the driver side, front wheel well. Could this mean there is an issue with my suspension, such as needing new springs and struts, or other issues like tie rod or CV joint?

There has never been a knocking noise until they replaced the brake lines up front, a knocking noise for the first couple of days, then nothing for the past 6 months. Now it's the same knocking noise, but only when coasting, not during acceleration or braking. Could it be engine mounts too? Thanks for any suggestions!

 

Knocking down by your feet? Check the bushing for the anti-sway bar where it goes up under the car on the driver's side. Easiest to see with the wheel removed and a strong light. (A 100 watt compact florescent in a drop light works well. Won't burn you or start fires either) On mine the aluminum bushing broke allowing the anti-sway bar to hit the sub-frame as the car bounced around normally. With the car jacked up (and secured with jack stands) the anti-sway bar will rise up away from the bushing mounting point if it is broken. If it's not broken the bushing will be secure to the sub-frame via a single 10mm bolt and the anti-sway bar will be held close to the sub-frame.

Other knocking sounds encountered: Up high was the strut mount and bearing. Knocking sound from behind glove box turned out to be the pax side strut mount and bearing.

Bad motor mounts: I remember this mostly as the whole car shaking with your foot on the brake with the car in gear.

There are several other potential problems too. From a bad CV axle to a worn out ball joint to worn bushings on the lower control arm. You can test for movement with the car up on jackstands while you try to move the tire.

 

It feels as if the knocking is more prominent behind the pedals, so I figure its on the driver side. I've tried to listen as well while going slow and the sound is much more prominent on the driver side, up front. when testing for movement, what am i looking for? I will check the antisway bar bushing wednesday. I need to get some jackstands. Are there any repair manuals that I can purchase in store for a 2001 S40? I've only found one online, from rockauto.com.

Also, wouldnt the sound be constant if it was the antisway bar? Not just during coasting? I dont really hear the knocking much while going over bumpy roads either.

 

For books I have only found the European version of Haynes that IPD sells. I did buy VIDA later due to having 2 Volvos and needing more information. It only works with 32bit Pro version of Windows, XP Pro and 7 Pro. Does not work with 64bit versions.

Testing for movement is kind of generic, works for any car. With the car jacked up and secure, grab the tire at 12 & 6 o'clock. Try to rock the tire. You do not want any movement although there may be a tiny bit as things wear out. A worn ball joint and/or wheel bearing will show itself here. Then grab the tire at 3 & 9 o'clock. Again try to rock the tire back and forth. Here worn steering components will show themselves with excessive tire movement. If you find too much movement then get a helper to wiggle the tire while you look behind it with a strong light.

For the broken bushing on the anti-sway bar I'm just suggesting what has already happened to me twice (once each side). It's a quick check and you can also look at other components while you are in there. Stuff like loose bolts and bracing. Also a good time to crawl under and look at the bottom 2 motor mounts. Is the rubber cracked? You have a knock under your feet. It's there somewhere......

 

So I checked the bushing, no damage I can see. No free movement with the anti sway bar either. No movement regarding the tire from 12-6, or 3-9. I have noticed the engine is making the car shake a bit more than when i first got it while stopped and an in drive. I tried to create the sound while the car was on the jack stands. No noise even with turning the steering wheel while tires were spinning. Noticed that weight distribution makes the noise louder during left hand curves, but pretty much goes away during right hand curves. Thinking its putting pressure on whatever is loose/broke. I haven't changed my struts or springs ever since i've purchased the car back in Oct of 2000. Could it be a combination of needing new motor mounts, and new struts and springs?

 

I just had a friend listen to the car while driving. He suspects the ball joint due to just replacing a ball joint on his Eclipse and having the same kind of sound. Could the ball joint be the problem. Also, how would I be able to check besides the actual knocking noise? My friend states to get under the actual car and use force to try to move the ball joint around. He says it shouldn't move at all. If this is the case, how long would it take for me to replace, or how much would it cost for a mechanic to replace?

I check the tire movement while on the jack stands and no movement 12-6 nor 3-9. From what I've read, if the 12-6 movement is over 15 degrees, the ball joint has failed. Is this correct?

 

If the ball joint is bad the tire will move. This also means your steering will be very loose too. How does the car steer at speed?

Since you mentioned the shaking with the car in gear have you looked at the lower motor mounts? Upper mounts? The motor mount over the trans is close to the anti-sway bar mount.

On my 2005 the car made a nasty knocking noise under acceleration. After much searching I found the upper motor mount on the pax side was sheared in two. The knocking was metal-on-metal as the rubber wore away.

Don't you just love a hard to find knocking noise? It's there somewhere...

 

For books I have only found the European version of Haynes that IPD sells.

 

Could the Ball Joint just be going bad, and then eventually my tire will move or if it's bad or going bad, there will be movement? I haven't checked the motor mounts yet, but that will be the plan for this upcoming weekend, if it's nice instead of snowing. If i purchase the european version for the repair manual, is there much difference than the one i can purchase on rock auto, in regards to tools, and measurements?

 

The Haynes manual at RockAuto is the same one that IPD sells. It's for the European model. Notice the picture says for Petrol cars and N Reg, both United Kingdom terms.

In my experience the ball joint simply wears out slowly. By the time it's so bad that you notice movement it's time to replace it. In other words, all ball joints have wear once they have a few miles on them. Only after many, many miles do they get loose enough that you can feel the tire move. If you can't feel the tire move then odds are it's something else causing your knocking noise. JMHO.