IT COULD BE A MUCH BIGGER PROBLEM!!
I had a similar with my 1990 S-10 Blazer but the cause was much more serious. On the passenger side, where the upper control arm attaches to the frame, the rear bolt tore through the bracket and was allowing control are to flex forward and backward as well as up and down, when I came to a stop and again when I released the brake from a stop. It would make a clunking noise. It had been doing it for several months. I thought it was just the floating front brake pad making noise when applied and released. I finally got it narrowed down by having someone apply the brakes while backing up while I looked under the front of the Blazer. I could see the sway bar hit the frame as the upper control arm rocked. After examining the bracket carefully the repair person noticed that the bolt hole had failed before and was welded. Now the area next to the weld had failed. As a temporary fix, the repair person modified (fabricated) a 1/2 inch thick steel bracket to hook under the existing bracket. He pounded the torn metal back in place and pit another 1/2 inch plate on other side of existing bracket and bolted it all back together. The extra metal required the removal of all the alignment shims on that bolt and adding a bunch of alignment shims to the other bolt. That was done last night. It seems to work fine and does not pull to a side. I'll be monitoring the bracket carefully for the next few weeks every time I go to drive to ensure it has not come loose. Getting the front end may now be a big problem because a professional shop will likely refuse to do it because of potential liability concerns. Next step will probably be to get a replacement bracket either from dealer or wrecking yard and have it welded to frame.
Has anyone else had this failure?
Since it was welded before, we suspect it may be a common failure.