Hello,

I'm currently facing a perplexing issue with my vehicle, and I'm seeking some expert advice to diagnose and resolve it. I've been experiencing a creaking sound, and after some investigation using sound probes, it seems to be originating from the upper control arm.

Now, here's what I've observed so far: the previous owner said that the upper control arm was already replaced, and upon inspection, both the rubber and boot look to be in good condition. However, the sound appears to resonate through the firewall after seemingly transmitting through the suspension, making me wonder if the sway bar or ball joint of the upper control arm is involved?

The creaking sound occurs both while braking and when I press up and down on the passenger side, causing the car to bounce up and down. Has anyone else encountered a similar issue? If it was the upper control arm, other than OEM, what is a a good brand? I'd greatly appreciate any insights, advice, or troubleshooting tips you may have to help me resolve this mystery.

Here is a video of it happening:
https://youtu.be/7zNOZgPVAJs
Thanks in advance for your expertise and support!

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Theseus

Instragram: doss_project
1984 300SD - 930 Blue, OM 617
Murfreesboro, TN

Theseus owned a ship in Greek mythology, and when a part of the ship needed replacing, it was replaced. Eventually, everything was replaced. Is it the same ship? (I own the car of Theseus. )

Mine has a similar creak. I changed almost everything.

In my case I finally traced it to the rubber bushings that hold the swaybar. I can make it go away temporarily by prying up the rubber away from the bar with a screwdriver and squirting some silicone oil in. Eventually it comes back.

I do the treatment every six to eight months. It gets really loud when I go up into a steep driveway or turn sharply on a slope. I originally thought it was ball joints and control arm bushings but after it was all said and done it was the swaybar bushings. I put in new ones and they still creaked.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles

My vote is guide rod mount. It is attached to the firewall down low and creaks like that.

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1985 300 TD 448K
1984 300 TD 278K

1983 240D euro 240k
1994 f-250 idi turbo 330K
1986 f-350 IDI
1987 F-350 IDI

1985 JD 1050 4wd
1965 IH 3660

Yeah. I had to change mine right after I bought my car. The boots were cracked and they were getting rusty. The hint from the op is that it happens while braking. That sounds like guide rod mounts. Mine do not make noise when braking.

All of the rubber in my front end is new. I’d keep changing things and the car would still make that creaking and knocking as I made sharp turns on slopes. I got frustrated and started spraying joints and bushings one by one with silicone oil. It was finally the swaybar bushings. Specifically the ones closest to the wheel wells. I had changed all four with new ones but they still made noise.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles

When I had a creak like that, my mechanic literally used a stethoscope while I turned a wheel to determine which part was bad. I forget which part it was but he changed it out and now it's All Quiet on the Western Front.

I can hear a creaking sound coming from the firewall. Based on my previous investigation, I determined that the sound is originating from between the ball joint and the sway bar on the upper control arm. I did not find any issues with the lower control arm. I previously inspected the right side sway bar bushing and it appeared to be in good condition. However, applying silicone oil did not resolve the issue last time. Interestingly, the sound sometimes disappears, although I can't be certain, but it may be related to rain.

__________________
Theseus

Instragram: doss_project
1984 300SD - 930 Blue, OM 617
Murfreesboro, TN

Theseus owned a ship in Greek mythology, and when a part of the ship needed replacing, it was replaced. Eventually, everything was replaced. Is it the same ship? (I own the car of Theseus. )

There are multiple bushings in there. 4 I think. It has been awhile. Aren’t there another two against the firewall?

Spraying may not be enough. I jam a small screwdriver in between the sway bar and the rubber and shoot silicone oil inside.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles

I often have had creaking sounds from the firewall on my W123. Those would have come from the guide rod mounts. Never were an issue and sometimes the creaking would go away for long periods. We did eventually replace those, but only because we were in there replacing other stuff. Some silicone spray might help, but to be effective you may have to disassemble?

On my 107, I had a creaking sound. Mainly when making slow tight turns. After replacing almost the whole front suspension, noise was still there . Had several shops and mechanic friends look at it with no answers. I finally found it! The subframe mounts were relatively new (several years) and the bolt torques when I checked were correct. However, that's where Loctite can cause a problem! I removed the bolts one at a time, cleaned them up, applied fresh Loctite and retorqued them to spec. Creaking noise gone! As the mounts wore in, the bolt tension was reduced and allowed the subframe to move.

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

Just get a finger pump spray bottle full of any Armor All type Plasticizer product and saturate the offending parts. Jack it up first so the wheels are hanging. That is all.

Started raining lately and the creak went away for a day. It’s come back again. I have my chassis creak detector and will give it a hookup at various points in the next few days to see based on feedback.

Have you checked the rubber on the lower ball joints. Those are highly suspect on high mileage older cars. Mine were making the creaking noises before replacement. Do you have uneven tire wear?

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Chris
84 280sl
82 300d euro

Hey the armor all tip reminded me that my 126 has those funny rattles in the back doors where the plastic and rubber rubs against the metal and squeaks. I wiped down the seals with tire foam which is kind of like armor all. It killed the door rattles.

Okay back to suspension rattles.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles

Broken spring , half or a quarter of a coil broken off and the creak you hear is the broken ends actually rubbing against each other … the noise always goes away if you pour water on them.

I was going to post about this.

I did lower ball joints on my 1991 350SD back in May. A few thousand miles later the guide rod on the right got real sloppy. So I replaced the guide rod mount, two big bushings, LCA bushing. Since then I get a groan at the firewall when steering.

I have not yet gotten an alignment because I want to do the same job on the opposite side so it all stays balanced in terms of age and condition. However the car drives straight and true. I don’t really know how i could have messed up the guide rod job so not sure what the issue is. Hoping for some ideas.

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Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)

Funny thing you mention this, I did a quick check yesterday with my probes. Turns out it is the lower area that is louder. Firewall is louder on lower side than near dash. Unfortunately, the creak resonates all over the frame, lower control arm, pivot, steering rods.. So, yeah. Gotta investigate this more.

__________________
Theseus

Instragram: doss_project
1984 300SD - 930 Blue, OM 617
Murfreesboro, TN

Theseus owned a ship in Greek mythology, and when a part of the ship needed replacing, it was replaced. Eventually, everything was replaced. Is it the same ship? (I own the car of Theseus. )