Thumping noise - 2003 Corolla

Getting the car ready to drive 1500 miles cross country, I took the car to a mechanic for a check up. I asked him to pay particular attention to a thumping noise from the right front side below the floor every time the car goes over a small bump at low speeds. The car has 128 K miles. He tells me everything checked out fine except the attachment points of the sway bars are worn and that is the cause of the noise. He said that apart from the nuisance factor its not a safety issue and that I could leave it alone. Alternatively, replacing the bar/s would cost around $300.
What is a sway bar and what does it do. Anybody concur with his opinion? I’m planning to trade this car in about a year from now. Till then it will be mostly used in city driving and commuting. It will be driven around 12K miles a year.


“attachment points of the sway bars are worn” . . . ?

Is he saying that the sway bar brackets are worn?

Is he saying the threads on the frame are worn . . . where the sway bar attaches?

My general philosophy is car makers do not spend money putting in useless parts. $300 is pretty cheap to make sure there are no issues.

A sway bar keeps the car from leaning (rolling) too much when you make a turn. If the end links are worn, you can get a thumping sound, but your mechanic is right in that at this time it is more of a nuisance than a safety factor.

However, some Toyota’s, the sway bar doubles as a training link. The trailing link keeps your wheels from moving longitudinally with the car. This is not the case with your Toyota though.

URGENT update. My daughter also owns a 2003 Corolla that makes that thumping sound on the passenger side front. I visited her this weekend and decided to take a look at it and from what I found, if yours is the same, it is not the sway bar or its links.

The sound is the engine cradle, aka subframe bushing has burst or the bolt holding the subframe has come loose. You can see this for yourself by turning the steering wheel all the way to the right. Then look behind the wheel and you will see a vertical rod about 1/2" diameter and a foot long with ball joints on each end that goes from the top of the strut down to the sway bar.

Right behind this vertical bar, about 3-4" from the bottom, you will see a black rubber bushing about 2" in diameter that goes between the subframe and the body of the car. Now have someone push the bumper up and down and you will see the subframe moving up, fully compressing the bushing and hitting the body of the car, and you will hear the sound as well.

I am going to investigate this further, but at the time I discovered it, it didn’t seem particularly dangerous. But now I am having second thoughts. If it is simply an air filled doughnut shaped rubber bushing that has burst, then I am less concerned. If it is due to the bolt that holds the assembly together coming loose, then this could be very dangerous. Also if the constant banging were to cause the bolt to fail, it could also become very dangerous.

If that bolt were to break and the cradle fell down at that point, it could cause the front wheels to suddenly go out of alignment from the pull of the axles or it could even pull the axles out of the CV joints where they would spin around and potentially do a lot of damage.

Have your mechanic check this out and if he thinks that the bolt is tight and not likely to break, then let us know. I will update more when I get back to my daughters to check out here car again. The subframe is captive, that is a failed bushing will not cause the subframe to fall out and the bolt looks to be pretty hefty, but I am going to look into this a little further myself.

Keith. Thanks for the detailed description of the bushing. I looked underneath like you described but could not locate the “black rubber bushing about 2” in diameter that goes between the subframe and the body of the car". The boot at the lower end of the 1/2" rod on the right side looked OK except had a little grease on it, whereas the one on the left was dry. All the bolts holding the rod and the other links were tight. Also, when I push on the right front corner of the car I don’t hear any bumping noise at all.
I’m wondering if this noise is the dust shield under the fender resonating when the car goes over a small bump at low speed.
I look forward to know what you found with your daughter’s Corolla

I’m going to try to get down to see her sometime this weekend to do a little more checking myself, I will take my camera and get a pic or two.

I have to eat a little crow here, it wasn’t the cradle assembly bushing that was loose. It also wasn’t the sway bar links. I actually don’t know for sure yet, but I had quite a bit of time to investigate and teh thumping is coming from either the strut assembly or the upper strut mount. I’m not sure which, but the car handles good and the struts stop all bouncing immediately after release.

I do not think it is dangerous, even if it is the upper strut mount. I have had upper strut mounts completely separate the two halves and they don’t fall out of the car until the strut is unbolted from the steering knuckle. In fact, until they are unbolted, compression holds them in place so they can’t move.

The sound could also be indicating that the strut will soon need to be replaced, but for now it is working just fine, just that annoying thumping sound.

EDIT: In looking at new struts for my daughters car, I found that there is a bumper that fits inside the dust boot. Since the dust boots are torn on my daughters car, it is not holding the bumper in place, so the sound could be the bumper hitting the bottom of the strut mount. If that is all it is, then I really won’t worry about it. Not sure I want to disassemble it to find out for sure.

Took another look today, I am now sure it is the upper strut mount, but I still don’t think that it is dangerous.