I've noticed that lately my car has been making a sort of knocking or thumping sound from the front suspension. At first I thought it was something to do with the struts so I took a look and both front strut lockdown nuts are still firmly in place and the strut tower bolts are all tight and firm, no budging in there. Any ideas?

edit: The springs and shocks are new, with less than a year on them.

 

my first guess with the information that you provided would be bad bushings on the idler arm. raise teh hood, walk to teh passenger side and push down on the right fender and compress the suspension. if the idler arm bushings are bad you will hear the idler arm clunking when you compress teh fron suspension. you may be able to hear it clunk if, with the engine off, turn the steering wheel side to side quickly.

if thats not the culprit, when you changed the front struts did you replace the bearing plates (srtut mounts)?

 

if the car is COLD, you can open the hood, reach down and pull on it. if it moved up and down, then its bad

 

Whats the idler arm look like?

Also, what is the strut mount/bearing plate?

 

What's the FSM look like?


Hint: Look in the front suspension section.

 

When you installed the new struts, were you careful to make sure that the insert was aligned so that the cap nut (the huge one) could fully seat? If the insert is not aligned, then it can seat against the insert, then later the insert shifts into the correct position and you are left with internal slop.

Also, was there a spacer that was needed inside the strut tube? I can't remember which strut inserts require them, but I know some do.

And, it can be tough to tell if that top nut is tight. This is because the spring tension will take up any slop that may be there until you hit a bump or other obstacle.

And, check the bolt that runs through the bushing on the A-arm (where it joins to the cross member).

That's about all I can think of off the top of my head that hasn't already been mentioned.

Best of luck.









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Mine does the exact same thing. I know it's not the steering as everything is new, tie rods, pitman arm, and idler arm. The previous owner had new Monroe Sensatracs up front. They bob and weave on the highway. I get a knocking noise from them. I doubt they are blown. Now I bet they were installed wrong. No matter, I am going with new springs and shocks soon. Also, my front driver's side sits a good 3/4 inch lower than the passenger front.

 

Does it make the noise when you bounce the nose by hand while the car is sitting still?

If yes, that usually eliminates anything brake, wheel, or bearing related.

Only time I've had moving rattles was when I found a loose center cap on a front wheel (tire place had put the spring retainer in backwards). But that's a higher-pitched kind of clinking sound.

 

check the rod that's bolted to the lower control arm and attaches to the frame at the front with bushings. a friend had the rearward nut on the bushing end work loose causing his noise.

 

Is it making a clunk over bumps, when you steer, hard cornering etc...?

On mine, after replacing front struts, they used an aluminum nut to hold the strut down (first and last time I had someone else fix my car). That aluminum one couldn't be tightened properly, and it ended up that I needed the stock steel nut back in there. It would make a clunk just turning the wheels right and left since the force on the strut would move a bit.

So I figured out that was together there was still a little slop between the spacer provided and the strut cartridge. I added some shim stock to make up the difference and made it a friction fit / press on and all was normal.

 

The cap nut (strut lockdown nut?) is tight against the body of the strut tube. I believe I used one spacer on each strut. If this is the case, does that eliminate this for the potential problem? I really, really don't want to redo the front struts.

I notice it particularly when the suspension 'decompresses.' For instance turning right onto my street, the road tips down at probably a 30* angle and I always hear it then.

 

check that idler arm. its bolted to the "frame rail" on the right side of the engine bay via two bolts and two nuts. i can post a pic if you'd like. eliminate this part first as its a VERY common part to go bad and will exhibit symptoms as you describe.

 

Mine knocks on compression. Like the struts are settling....

 

Just went and jacked with the idler arm. It seems to move up and down about 1/16" of an inch, as well as making an audible 'knocking' sound with just me yanking on it, so I'm pretty sure it's the culprit.

So does it just need new bushings?

 

I got a MOOG idler arm....it's waaaay heavier duty than the crappy OEM Idler arm. Uses no bushings, it has a greasable ball joint.

 

Alright awesome I'll probably do the same. Is this a involved repair or is it fairly simple? Just wanting to get a ballpark of how much time I'm going to need. Does it require an alignment afterwards?

 

Amazingly simple. The hardest part for me was separating the steering link from the idler arm, but nothing a good wack from a hammer wont fix. In theory no alignment is needed after, but my steering wheel was slightly off center after I replaced the idler arm, but since I planned on replacing all the tie-rods and stuff later I wasn't too worried. I got it aligned when I did all that.

 

Alright awesome. I guess the best plan of attack would be from the bottom?

 

Yep

 

& don't freak out when the studs that mount the arm to the frame start to turn with the nuts... because they're not studs. Bolts that go right thru the frame. You can get a wrench on the heads inside the wheel well.

(scared hell out of myself that way once...)

 

I recently changed my inserts and went with re-speed coilovers. I had the same problem, I could not figure it out. I jacked up the drivers side and pushed down on my insert (where the locknut is on the top of the shock) and it went down about a 1/4 of an inch. I found this strange. After scratching my head I realized I forgot to put back one of the spacers. One spacer has a wider inner diameter.
I put that spacer together with the smaller one and the knocking is gone, hopefully you made the same silly mistake as me.

 

I will look at this as well. I kind of think it's unrelated to the struts though, because only in the last few weeks has it started making this sound. I did the suspension over a year ago.

 

I will second the use of the Moog idler arm. And I swapped mine from the top of the car, everything was well within reach.

You can get the part from Mazdatrix for about 80 bucks if I remember correctly, or from www.rockauto.com for about 50 bucks.

 

Moog's unit is a great part! for al ittle cheaper you can get aftermarket units. if you go that route, i will reccomend napa's unit. runs about $65 and does hold up extremely well.

 

the lazy man will buy the $10 of bushings, and you can replace them from the top, no jacking up car required.

10minute job.

i'm sure the MOOG is a better part, but its probably a 30 minute job to install, not to mention you have to BUY the thing