'97 Bonneville Front Suspension Knock

[markr]

Have a light knocking noise in the front end. It coincides with the wheels going up and down over bumps in the road, mainly at low speeds. Not very noticeable at highway speed. Seems worse in cold weather. Have checked out all ball joints, tie rods, stabilizer links---everything is tight. Leads me to believe it may be in the struts. Could the struts have a loose spot in them somewhere or could a bad mounting component of the strut cause a noise? Has anyone run across a similar problem. Can't find anything loose that would cause a rattle.

[PLAGUE PHANTOM]

Friend had this same issue. He replaced the struts and the coil springs and the knock was gone. His car was a 1995 Bonneville SSEi.

[willwren]

It's more likely the upper strut mounts, but if your front struts are older than 100k miles or so, I'd do them at the same time.

Quickstruts can save you some time and effort if you do the job yourself, but you'll need an alignment regardless when the work is complete.


Do NOT rule out subframe bushings though. Take the time to inspect them for rust, particularly since you're in the rust belt (OH). I'm giving you things to check, not a concrete diagnosis (If I was closer, I'd come over and help you though!)

[willwren]

Another idea just hit me (at 4am believe it or not).

Spray some white lithium grease into the tops of the strut towers. The strut caps just pull off. You can get it at most auto parts stores, and use the straw. Work it around in the upper bearing/mount. See if the noise changes or goes away. If it does, it's the mounts.

[markr]

Ok, since originally posting this, I have recently replaced the struts, strut bearing plates, and strut mounts. I thought surely this would take care of this (needed this stuff anyway). Nope! Noise still there. Car had alignment after all this. Nothing else shows bad in steering. The noise coincides with the wheels going up and down on bumpy roads at low speeds. Not a real metallic clunk, more of a padded,plastic or rubber on metal clunk, but sure does seem to transfer up through the area of the strut towers. Anything in the inner fenders that could be loose and bouncing? Stabilizer links are good. I can hear a noise when I rock the front end pushing down on the front fenders, but it is hard to replicate without the wheels actually bouncing up and down. Got me puzzled!

[MattStrike]

Did you check the sub frame bushings?
I would inspect the sway bar mounts on the sub frame to make sure the rubber bushings are intact; also you might have a hollow sway bar. The ends on the hollow bars are prone to splitting apart. A good test for sway bar noises is to find a speed bump or something and compare the noise when both tires hit at the same time, and each one by itself. The goal is to get one side to compress and the other to stay level to see if you can isolate the location of the noise. Also, having all 4 wheels on a flat surface tends to make the sway bar sit in a neutral position so you cant tell visually.


If those bushings are bad, they could cause the clunk.

[markr]

OK! Thanks for the info! Will check! Sub frame bushings LOOK to be OK, but I will inspect further. What about A-arm bushings?

[MattStrike]

Possibly... I doubt it though, I haven't seen control arm bushing fail yet and I'm pushing 250k miles in the snow belt. Best way to find out is to check them that way you know for sure.

[razmatazz]

probally already check this but just putting it out there. just double check that nothing is loose under the hood. like a reserve tank or battery. like i said just throughing it out there cause i had the same mysterious "knock" in my rear end. i spent a day replacing struts and looking through the suspension.... turned out to be that my spare tire was loose..... i dont think i could of cussed any loud than i did when i found that out.

[Bob Dillon]

turned out to be that my spare tire was loose..... i dont think i could of cussed any loud than i did when i found that out.

Quit whining-it needed them anyway.

[razmatazz]

lol ya it prob did. I wasn't whinning. It was more like a "really that's what is was" feeling

[markr]

Did you check the sub frame bushings?
I would inspect the sway bar mounts on the sub frame to make sure the rubber bushings are intact; also you might have a hollow sway bar. The ends on the hollow bars are prone to splitting apart. A good test for sway bar noises is to find a speed bump or something and compare the noise when both tires hit at the same time, and each one by itself. The goal is to get one side to compress and the other to stay level to see if you can isolate the location of the noise. Also, having all 4 wheels on a flat surface tends to make the sway bar sit in a neutral position so you cant tell visually.


If those bushings are bad, they could cause the clunk.

I'm leaning more towards these bushings. They are in the area that the noise seems to be coming from. Also, today. I took notice that there was hardly any noise on a curve (as one side would sort of tighten up as the car leaned), as compared to flat, straight road where the sound is noticeable, especially since the stabilizer links are tight, there would be no play there, and the noise WOULD coincide with the wheel bounce over a bump or rough road. Makes sense. I never knew there was a hollow sway bar. That would tend to even amplify the sound! I have seen even the solid bars break. Can you tell a difference just by looking? I would almost bet that it is these bushings. Thanks for your suggestion! Have you ever changed these (bushings) before? Just wondering what I would get into here.

[willwren]

I strongly doubt the swaybar center links as your problem. Even if the rubber wore out enough for the bar to move, you'd never hear it. Nor have I seen any car on this Forum since 2002 that REALLY needed to replace them. They simply don't wear out, and when they do, they don't matter.