Getting the car ready for a long road trip at the end of the week, and I noticed a few days ago that the front brakes were "clunking" when starting from a stop and when low speed braking. At first I thought it was a stuck caliper, but after a little investigation it turns out to be a slide pin seal issue that was caused by using the wrong grease.
I usually use CRC brake grease on most of my cars, but in this case it's not the right solution. These GM calipers have neoprene bushings on the slide pins and after just a few months since I replaced the brakes, the grease has caused the bushings to swell, and the dust boots to deteriorate. There's something in that brake grease that isn't compatible with these GM designs.
The solution is to remove the caliper bracket and clean it thoroughly in the parts washer, with special attention to the slide pin bores. Then lube with NAPA Syl-Glide silicone based brake grease that doesn't react with the neoprene bushings and cause swelling.
Boots and bushings are deteriorated and swollen -- causing the caliper to stick and clunk.
Everything cleaned and ready for reassembly -
This is not an uncommon problem with these types of GM calipers that use neoprene bushings on the end of the pins to keep the caliper from making noise. Some GM calipers have a single such pin (the other without a bushing), while others have the bushings on both pins.
Although a common problem, I didn't know about it until talking to a pro-tech friend of mine. Learn something new every day
I also replaced the right front shock/strut assembly because the bearing was making noise. It's a fairly new strut (less than a year old), but NAPA stood behind it. They gave me a replacement without any big drama.
Old one out -
New one in -- not that hard on these old Cadillacs
Monday I'll go for an alignment, and hopefully this DTS is ready for a long road trip at the end of the week.