Why is there a clunking noise only when turning hard left, e.g., when parking or making a U-turn?

Check the cv shaft boots, if they are torn the grease inside will have come out and now the joints inside are worn out. Worn cv joints will cause noises when turning.

I would tend to believe it's more likely a worn sway bar bushing or link if it's a rattle or a small clunk, if it's a loud clunk probably a strut, try bouncing he back of the car when parked, if you get the clunk probably a strut if only when driving,turning,braking probably just a bushing on the sway bar

I know this website www.reliable-store.com that i get manuals from, and they have all models online that solve all simple/technical problems like professionals

I also brought for my 1989 BMW, such old model, they had it and it was very good manual. Go ahead, I bet.

Check the front suspension ball joints and steering joints. Check wheel bearings and adjustment. Check shock absorber mounts for condition . Check steering insert condition and top mount rubbers and bearings if McPherson strut set up.. If you have a steering shock absorber then check it's condition and mounting

I would expect to find a ball joint, upper strut mount, or control arm bushing to be bad rather than the axle joints. Usually if a CV joint is going you hear a clicking noise as the wheel is turning not just one clunk. One clunk usually means something is shifting.

You're probably going to need a shop to look at the front suspension.
With extra weight in the back, the front could have been up enough to cause something to come loose such as a strut mount. And that could happen just from old age without the extra weight.
If it is a strut mount you may not want to change it yourself since the strut has to be removed.
I would suggest getting a couple of estimates, or more. In most cases the shop will want to do a front end alignment too because of having to remove the strut.

If your car has struts, its probably the upper strut mount. Don't rule out a broken spring.

Most likely the cv joints need to be replaced. Also check struts.

the car is aging

there are other bushings and ball joints to make noises at that speed

the top rubber mounts failed for a reason

if i were on that job i would have replaced both gas struts
at the same time....

not much structure to the top strut mounts
see pictures in link
Strut Mount Early Small Chassis Audi Density Line

I had the same problem with my 2002 Town and Country Limited. I took it to the mechanic and had the sway bar links and ball joints replaced and still had the same clunking noise when going over bumps at low speeds. The van sounded great on the highway, but country roads were horrible. I was about to replace the struts and pay another 700 dollars when i read somewhere that the sway bar bushings could wear and cause the noise. I took it to the mechanic and he said absolutely not it would be a waste of money. Being the stubborn guy I am, I went to NAPA and bought the two bushings for 12 dollars and replaced them myself in an hour. I took the van for a test ride and the noise is completely gone. Please ignore your mechanic and replace the bushings ASAP! Pretty cheap try even if it doesn't work.