Upper Control arm bolts coming loose - design flaw?

[Jeffrey Burland]

I searched the messages, but didn't find anything on this. A few people have had a problem with 65-70 upper control arm bushing bolts coming loose after replacement. I could see a problem if the smaller size was used or bolts not torqued correctly. They're saying vibration and vertical movement of the arm will loosen the bolts and they need to be checked. Has anyone heard of this or post any links to reports of this?

[dadscad]

Jeff,

Most instances when the upper control arm bushing retaining bolt loosens with suspension movement, it is caused by one of two things. First could be improper torque of the bolt. The most common thing is, the bolts were tightened while the suspension was hanging in the air. The bushing bolts must be torqued with the car sitting on the ground supported by the suspension. If the bolts are tightened otherwise, the movement will loosen the bolts or tear the rubber in the bushing. Lower bushings should also be torqued with the suspension supporting the car.

HTH,
David

[Dave Shepherd]

Jeff,

Most instances when the upper control arm bushing retaining bolt loosens with suspension movement, it is caused by one of two things. First could be improper torque of the bolt. The most common thing is, the bolts were tightened while the suspension was hanging in the air. The bushing bolts must be torqued with the car sitting on the ground supported by the suspension. If the bolts are tightened otherwise, the movement will loosen the bolts or tear the rubber in the bushing. Lower bushings should also be torqued with the suspension supporting the car.

HTH,             Excellent advice, also lock washers may help.
David

[Wayne Womble 12210]

I am not sure about this model Cadillac, my expertise is Corvettes, but if they are the typical rubber bushings that most GM cars of the era had, they never should come loose.  As David said, lower the suspension and tighten them.  The bolt and  washer tightens against a serrated spacer and locks itself.  If its coming loose, it wasn't tightened enough. 

I am not sure if urethane bushings are available for these cars, but if they are, and they are used, you mush use lock tight and make sure they are good and tight. The design of the urethane replacements are different and without lock tight, they will work loose quickly.

[Glen]

Wasn’t the nuts on those bolts the self locking type?  They were slightly deformed to keep them from vibrating loose. 

Or am I talking about something else?

["Cadillac Kid" Greg Surfas 15364]

Glen,
I believe you are correct.  Usually this problem seems to occur when someone replaces the upper bushings and doesn't use the correct bolts.  A "design flaw" is something that occurs immediately, not 45 years after manufacturer.  I for one am amazed at the structural integrity of Cadillac front and rear suspensions of the mid '60s and later.
Greg Surfas