97 Corolla

My 97 Corolla with 97K miles makes a loud knocking sound w/c appears to be coming from the left wheel. However, the sound is not always there. Heard it 3 weeks ago while driving around 5 miles from home. The following day it was totally gone. Last week or two weeks after I first heard it, it came back–again while driving w/in a 5 mile radius. The following day, the noise was gone. I wanted to take it to my mechanic but I won’t be able to let him listen to the noise if it is not there when I go to his shop–unless the noise comes back on my way to the shop. What could it be? Should I wait for the noise to be consistent before taking the car to my mechanic? Is it a safety issue? Thanks in advance!

If the knocking is rhythmnic in nature this often points to a CV joint, which is part of the halfshaft. Since it’s on the left side try making a fairly sharp right turn and see if the noise reappears. If it comes back it’s likely the halfshaft.

Other possibilities could be a rattling ball joint, sway bar link, and in some cases even a loose wheel cover (on cars equipped with steel wheels) can pop like this.
The one critical thing is the ball joint. This is the most serious suspension safety issue there is and these should be inspected quickly just to weed that possibility out.

If you’ve ever seen a car on the side of the road with a wheel splayed out flat a broken ball joint is usually the cause of that. Hope that helps.

Thanks for the advice.

I heard the noise again today. It happened when gradually accelerating when coming from a full stop. Today it sounded like it was coming from behind the brake and accelerator pedals. Does not seem like from the wheels. No change in the noise when making sharp turns to the left and to the right. Once the noise started, it went continuously.