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2009 STS-4 V8
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236 Posts
Discussion Starter #1
As the title says, I've developed a suspension clunk in my front right wheel. I just rolled over 120k. Both rear shocks are new, and the front left strut was replaced at around 40k after a crash. It has the F55 Magnetic Ride Control and I've installed D3 Lowering Springs.
I just replaced my lower control arms and shortly after that it started. I noticed the ball joint on the front passenger side had split after only 6 months, so I replaced that control arm again thinking my clunk was a bad ball joint. It wasn't.
The sway bar links are new and tight, control arms are new and tight, wheel hub is new and tight, everything is tight, the springs are installed correctly... I did notice a fair bit of oil on the dust boot but from what I understand, MRC Shocks will "Burp" oil constantly throughout their life, and a GM bulletin says oil shouldn't be a concern unless it's running down the entire strut body.
The clunking only happens on really large bumps, like big dips in the road, driveways, or certain potholes where it goes uncompressed>suddenly really compressed. And it's a pretty LOUD clunk at times. There's no steering groan and no clunking at lower speeds.
For now I cleaned the strut off with degreaser and water to watch for more oil. This is a perfect excuse to get some track coilovers, but I don't want to replace a working MRC system if it only ends up being a strut top or something. Any ideas? I'll try to get videos and pictures as things go along.
 

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08 STS 1SG HUD ACC F55 AWD, 08 STS 1SG Platinum HUD ACC F55 RWD
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436 Posts
Just some thoughts. Has your lowering springs allowed the shock to reach max compression with the concurrent clunk? Strut top was a good thought on your part. I have seen the hard rubber ripped by one hard landing to many. Also the top nut on the strut can become loose and cause a clunk. I hope your mechanic tightened the LCA with the weight of the car on the wheels. To do otherwise puts the bushings in a shearing torque which destroys the bushings in short order. Check for a loose lower strut yoke. I would be glad to take your working MRC off your hands if ya decide to go to track coilovers. Keep us informed and we love pics. It really did not happen unless you produce pics. Good Luck.
 

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2009 STS-4 V8
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236 Posts
Discussion Starter #3
Just some thoughts. Has your lowering springs allowed the shock to reach max compression with the concurrent clunk? Strut top was a good thought on your part. I have seen the hard rubber ripped by one hard landing to many. Also the top nut on the strut can become loose and cause a clunk. I hope your mechanic tightened the LCA with the weight of the car on the wheels. To do otherwise puts the bushings in a shearing torque which destroys the bushings in short order. Check for a loose lower strut yoke. I would be glad to take your working MRC off your hands if ya decide to go to track coilovers. Keep us informed and we love pics. It really did not happen unless you produce pics. Good Luck.
I do all of the work, but yes, I did tighten the control arm with the suspension loaded.
The lowering springs are designed specifically for the STS with Magnetic Ride Control, and I've never had a clunk until about a month ago. I installed the springs in I'd say October last year. They don't even drop the car very much.
The top nut is tight, the yoke was gunned down with an impact so that's definitely tight. I will double check though.
Here's a video:
 

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08 STS 1SG HUD ACC F55 AWD, 08 STS 1SG Platinum HUD ACC F55 RWD
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436 Posts
Both top and bottom of the yoke?
 

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2009 STS-4 V8
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236 Posts
Discussion Starter #5
Both top and bottom of the yoke?
Yes, the tops always give me trouble, but the clunk never went away, even after the removal, cleaning, and reinstall action of the yoke after replacing the control arm again. I'll dive into it this weekend assuming this heatwave doesn't kill me. I'm going to remove the strut and check it, and also take it for another alignment. Long story short, when I originally replaced the control arms, Pep Boys never tightened anything after they aligned it, so they ended up buying me 4 new Blizzak tires and paying for a dealership alignment after my tires got destroyed from my car just steering however it wanted at 80mph. So that $100 alignment ended up costing them nearly a grand.
 

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08 STS 1SG HUD ACC F55 AWD, 08 STS 1SG Platinum HUD ACC F55 RWD
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436 Posts
Look up Nord Lock washers. Specifically they keep the bolts from working loose. Expensive but a good thing. Good Luck
 
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