Suburban '90-454, alternator strut rattles with AC
 

Hello Everyone,

I have a '90 Suburban with a 454. Yes, I am paying dearly for fuel, but the truck is still fun to drive on weekends. My problem "seemed" to start about 6 months ago when I had a new AC compressor installed, but was only occasional. With the AC on and only at idle, a tramendous rattle now comes from under the hood. Searched our Forum, and the term "AC Slugging" shows up as a cause for AC rattling sounds. Took the truck back to the AC mechanic and he said it's not the AC, but that it definitely sounds like a broked accessory bracket. I said, "How can that be, they're all steel." But it definitely sounded like a broken bracket to me also.

Went home and started looking for a bad bracket, and found the cause! The strut that goes from the back of the alternator to the driver side of the engine head. It's not broken, but it rattles on the bolt in the head. No matter how much torque I put on the bolt, it still rattles :eek:. The clearance hole is about a 1/16" larger than the diameter of the bolt (3/8 bolt). For the time being I disconnected the bracket (NO rattle!), but I know this is not a good idea, and not a solution.

Any suggestions?

A small stack of washers to shim the length of the bolt to apply clamping force to that there bracket? Wrong bolt for that hole?

Nullhead, thanks for reply. The bolt and strut are original, as I am the original owner. Now you have a good point, because the male threads in contact with the strut are worn-down to the minor diameter, thus allowing more clearance with strut hole. I should try getting a new grade-8 bolt , and was even thinking of getting some sort of washer with "teeth" to help grip the strut.
Was also thinking of installing (pressing) a hardened bushing into the strut hole, that has a hole that just barely clears the bolt threads.

Honestly that sounds like far too much work lol ...

I'd just put a washer and a lock washer or some thread locker and call it a day.