Car 91 coupe auto... 75k miles bone stock other than some interior things normal maintanence all up to date...

I have a rattle that I have been chasing for months with no luck. I first it was every now and then, in the rear sounds like driver side rear to me. A lot of suggestions were offered but jacked up then and nothing is loose from what I can see. I drove it more thinking whatever it is it will get looser to the point it is obvious and it did to the point every bump produced a rattle. Jacked the car up to take a look and all is fine even though if you bounced the car it would make the noise. I could not see a good place to support the knukle that would not bind on something else and sit at ride height so everything in the same position as normal driving. I then get the bright idea to put the spare on as it is small enough to reach everything at ride height and weight on the wheel and it and the carrier were the first thing I removed to see if it was the rattle. Spare on car back on the ground and no rattle when bouncing the car.

I am lerry about even going around the block with the spare tire on though it looks ok but no doubt 20 years old. I was thinking to let it sit for a day and see if it settles back down and makes the noise again bouncing it. Or disconnect the sway bar link put the tire on and go for a ride around the block if it still makes it to take the shock off and do the same. At least it would eliminate those two possibilities. It does not seem like it could be the caliper as it is tight. It does not sound like a bearing as it is more bump than turning related. i will check the axle nut for laughs though doubt that is it but who knows.

It is not a hard bang sort of sound but more like something lighter. Two silly ideas could it be the rear glass as the weather strip is there but if I push hard on the glass I can get it to make some noise? Of cand someone hit you in a parking lot and break some plastic behind the bumper but not damage the car or scratch the paint?

I am up for ideas sorry about the long post but trying to answer as many questions up front as possible.
Dave

 

A few things others have found:

Sway bar bushings
Upper shock mount bushing

 

maybe this is a crazy idea... but are you getting any codes? you say when you switched to the spare the sound went away? could it be the TPMS? maybe give the wheel a rattle and see if the TPMS is rolling around in there. I suppose it's possible.

 

My money is on a toasted end link bushing. Bouncing the car may not induce enough motion to make it rattle. It's easy to pull the end link and take a look.

 

Thanks for all the quick replys!
End link bushing? Which one? Dog bone, sway bar, camber rod, tie rod, shock?
No TPMS took them out when I first bought the car as 1 was bad and no interest in fixing them. I do not remember which one but as a side note would sell the bunch of them for 150 plus shipping.

Shock upper bushing pulling the shock completely and driving around the block should settle that one pretty quick.

Sway bar bushings are they the ones between bar and knukle or bar and chassis that usually go?

Off to check axle nut and report back.

Dave

 

Ok not the axle nut set torque wrench at 205 ft lbs and clicked with no movement to tighten..

 

please PM on the sensors I will probably take them.

 

Not a hard job.

 

ok will give them a check tomorrow!
Dave

 

I have a very similar rattle going on... upper bolt on sway bar endlink was loose, I tightened it, but it did not help at all. I'm still stumped.

 

Let me know if you find anything. I am going to pulll the shock today and see if the shaft is loose or bushings loose.

 

I was thinking about swapping the shocks from L to R, to see if the noise moves as well.

I also was wondering if the FX3 wiring/connector was rattling around inside the framerail, I may wrap that with some sticky backed foam when I pull the shocks.

 

Dave,

I removed both rear shocks today, and swapped them side to side. No test drive yet, still have to do some brake bleeding (unrelated), but the top bushings were not as compressed as they should have been. I say this based on the specified position of the FX3 adjuster gear. The FSM calls for the top of the gear to be no less than 5.0mm from the top edge of the actuator mounting cup. Mine were about 3mm at best. So there was more compression of the bushings to be obtained. Not sure if it's going to help, but it certainly can't hurt.

I also found that all of my swaybar end link bolts were not as snug as they should have been. I think when I replaced the bushings, I planned to tighten them later on when the suspension was loaded, and probably just forgot about it.

 

Test drive today, the rattle is no different whatsoever. This leads me to rule out the shocks and swaybar endlinks. At this point I think I'll just crank up the stereo on bumpy roads

 

did you check the spare tire carrier for anything loose?

 

Mine has every part of that in the corner of the garage along with cd's bins for cargo areas ec everything that can move.
Dave

 

There are so many places it could be. Some thoughts:

ABS lines or something fell in by ABS pump in storage compartment
Fuel lines by frame, passenger side kind of by sway bar
Fuel door springs weak letting it flop
To heavy cargo bent hatch metal down slightly, contacts square frame part by sway bar
Parking break pads/brake pads without rattle clips

 

I had one in the back that took me forever to find.
The egg crate crash absorber ends are semi-floating.
Mine would bounce enough when I hit a bump to hit the aluminum frame piece cross member.
Fixed with some rubber u-channel and blue silicone, the egg crate is now glued to the piece it used to rattle against.

 

I thank everyone for all the thoughts I think I fixed it but only did a ride around the block that should have made it rattle. VetteMed mentioned the shock and I was able to take a little on that to get the 5mm clearance. I took out the rear sway bar everything looked ok but had an aftermarket one i never installed with poly bushings etc. and installed as I was close to halfway there. No noises but only a short trip and now I should change the front bar to match the new rear one. If this does not fix it in the end will report back.
Dave

 

A Steel Man Chassis Ear is a handy tool for diagnosing & pinpointing exact strange & hard to find suspension, body, & drivetrain noises Dave.
Newest models have 8 alligator style clamps- microphones.
Zip tie the leads under the car back to the black box solid state amplifier module. clamps- microphones are color coded along with the selector switch on the unit. Headphones provided with Kit.
As you drive your car, choose the microphone you wish to tune in & listen.
If thats not the noise, choose another microphone pickup.
Typically pinpoint the noise in under 10 minutes on a test drive with a Steel Man Chassis Ear.
Flat rate maker for an ex GM mechanic.
They give you just 1 hour paid time to find any noise.
warranty repairs or paid customer diagnosis time.
convince your local GM garage to let you borrow it.
God send of a tool to use for tough to find noises.
Used a Steelaman Chassis Ear 100's of times myself.