300E Front-end Knock/Rattle Sounds on Small Bumps

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Bob - 07 Feb 2005 19:14 GMT

The car is a 1989 300E with about 180,000 miles. When it runs over small
bumps on the road, it makes a rattle/knock sound. It is very annoying and a
little scary. I think it is coming mostly from the left (drivers) side of
the car.

I replaced a worn out drag link recently, and hoped that was the source of
the noise, but it wasn't. With the front end jacked-up, the front wheels
don't have any play in them when I try to wiggle them side-to-side or
up-and-down. While under the front end I replaced the steering damper too.
Everything got torqued properly.

Any suggestions on how to diagnose the source of the noise? Are there some
"bushings" that are known problems? How do you check them to see if they
are good/bad? Visual inspection?

Thanks,

Bob

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Al Bolton - 07 Feb 2005 21:46 GMT

Try the anti-roll bar bushes - quite a common failing on these cars; they
failed on my 260E and made some horrible clonks!

Al Bolton, G4VSQ
1990 500SE
1988 260E FOR SALE

==================

> The car is a 1989 300E with about 180,000 miles. When it runs over small
> bumps on the road, it makes a rattle/knock sound. It is very annoying and
[quoted text clipped - 14 lines]
>
> Bob

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Henry Kolesnik - 07 Feb 2005 22:27 GMT

If the front end is anything like a 126 there are is a compliance joint on
each side and they wear out. Do you hear a clunk on braking at real low
speed?

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73
Hank WD5JFR

> Try the anti-roll bar bushes - quite a common failing on these cars; they
> failed on my 260E and made some horrible clonks!
[quoted text clipped - 23 lines]
>>
>> Bob

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marlinspike - 08 Feb 2005 00:13 GMT

Whoa, i do on my 126. Is this the ball joints?
Richard

> If the front end is anything like a 126 there are is a compliance joint on
> each side and they wear out. Do you hear a clunk on braking at real low
[quoted text clipped - 27 lines]
> >>
> >> Bob

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Henry Kolesnik - 08 Feb 2005 15:10 GMT

On my 126 you could hear the ball joints squeak and groan when you got in or
out of the car. The compliance joints or track rod mounts are rubber joints
that keep the front wheels from moving back when you brake or verse visa.
When they are worn you get clunking on braking and acceleration. In my 83
300SD with 98k mi the noise of both the ball joints and compliance joints
went away when it rained and water got in. And water is what caused the
ball joints to go bad after the rubber boot cracked. I was quoted between
$900 and $1300 for parts and labor by the independent Benz shops. Seems
like they all use the same computer program for time beause times were
within 20%, but different labor rates, parts were within 10%. I was lucky
as I recalled seeing an invoice in a car that I tried out but didn't buy and
they used Tulsa Wheel and Brake. I called them and they did mine for their
estimate a little over $400, including alignment and that was July, 04 and
it didn't take anywhere near as long as the others quoted. Three long trips
and 12,000 miles later I have no complaints.

Signature

73
Hank WD5JFR

> Whoa, i do on my 126. Is this the ball joints?
> Richard
[quoted text clipped - 37 lines]
>> >>
>> >> Bob

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Bob - 08 Feb 2005 18:08 GMT

Thanks for the feedback! This group makes owning (and maintaining) the Benz
a lot more fun.

The car does not make the sound during braking or acceleration. The rubber
at the tops of the struts has a small crack around it at the top. I can't
imagine that that fine crack is causing the sound.

From the feedback so far, I'm thinking that I need to replace some bushings.
From Rusty's website: http://www.parts.mbz.org/ There are two bushing kits
I'm considering:

Front Sway Bar

L1049-36181 Sway Bar Bushing Kit Febi IN STOCK $15.45

Front lower control arm to frame:

L2040-34581 Control Arm Bushing Kit Lemforder IN STOCK $55.23

Here's the plan:

I will lift up the front end of the car and check the following:

1) Wiggle and inspect the sway bar to see if its loose in its bushings.

2) Put a second jack under the control arm and put some upward pressure on
it to see if there is any play where it connects with the frame.

3) Wiggle the wheels side-to-side, left-&-right, and vertically up-and-down
(in case I missed something the first time).

4) No one's mentioned motor mounts yet... but I will also check to see if
they are loose or broken.

5) Other ? ? ? ? ?

(I have a bunch of new parts sitting on the shelf in my garage that I
purchased online and didn't need... so I'm going to diagnose this one real
well before buying this time... :)

Bob
Murrysville, PA

> On my 126 you could hear the ball joints squeak and groan when you got in
> or out of the car. The compliance joints or track rod mounts are rubber
[quoted text clipped - 56 lines]
>>> >>
>>> >> Bob

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Richard Sexton - 08 Feb 2005 21:46 GMT

>On my 126 you could hear the ball joints squeak and groan when you got in or
>out of the car. The compliance joints or track rod mounts are rubber joints
[quoted text clipped - 11 lines]
>it didn't take anywhere near as long as the others quoted. Three long trips
>and 12,000 miles later I have no complaints.

The track rod mounts are reasonably cheap and easy to replace. The track rods
themselevs are nasty compicated expesive (very) things, but they can be
rebuild; there's a couple of ball joints in there. Unless the housing
is cracked you should never need to get new track rods. Most of the used ones
are buggered beyond repair, mostly from rust.

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Richard Sexton - 08 Feb 2005 21:43 GMT

>Whoa, i do on my 126. Is this the ball joints?
>Richard

Might be, easy to check. Could be track rod mounts or the track rods
themseleves.

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marlinspike - 09 Feb 2005 06:41 GMT

> Might be, easy to check. Could be track rod mounts or the track rods
> themseleves.

Well, I know my ball joints are bad so to speak (torn boot and a little
play), but my mechanic said come back in 5000 miles, so I did and he said
give em another 5000 (and he's not getting money on these check ups so it's
not that). It's only $275/side so I'm thinking I'm just going to have him do
it when I go home for spring break (I do a good amount of my own work
though...anything special needed for ball joints like a spring compressor or
something?) cause I don't like the thought of one corner of my car
collapsing on the highway.
Richard

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Al Bolton - 08 Feb 2005 20:11 GMT

Sorry, these are called "sway bar bushes" in US English. Very cheap and easy
to replace, well worth doing anyway, even if they aren't knocking now they
will...

Regards,
Al Bolton
======================

> Try the anti-roll bar bushes - quite a common failing on these cars; they
> failed on my 260E and made some horrible clonks!
[quoted text clipped - 23 lines]
>>
>> Bob

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T.G. Lambach - 08 Feb 2005 05:51 GMT

Suggest you inspect the stabilizer bar's ends and its rubber bushings,
also check the shock absorber bushings.

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Richard Sexton - 08 Feb 2005 21:42 GMT

>The car is a 1989 300E with about 180,000 miles. When it runs over small
>bumps on the road, it makes a rattle/knock sound. It is very annoying and a
[quoted text clipped - 10 lines]
>"bushings" that are known problems? How do you check them to see if they
>are good/bad? Visual inspection?

Get somebody that knows these cars and drive and stop it at very low speed
and have them look up there while it's moving. Whatever is rattling around
in there will be very obvious to them then.

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