Front end clunk: 240D

[mbzkid]

I searched.

The 240D automatic (the one in my sig) started making a clunk/pop sound early this winter. It's not my car, so I'll try to describe the problem to the best of my ability. I drive it from time to time.

The pop gets worse when the ambient temp. is low. I just drove it all around town in the 50 F weather today, and it was no where near as bad as it used to be. I was able to get it to make the pop sound when making a right turn and hitting a bump with the left wheel. This loads the left wheel.

It feels like the whole engine was shifting when making some left turns though.

When it was colder out, I remember it popping when braking and while making 90 degree turns. It would also pop the ledge at the bottom of my driveway. The worst being when making the 90 degree turns, though.

I can feel the pop in the passenger floor board with my feet, and also on the drivers side a bit. It can be felt best from the passenger side floor, though. I can feel it up near the front shock towers, all the way back to the trans mount at times. Very difficult to track down.

I first looked at the front suspension, but found no play at all, besides the typical gearbox wear.

Then I checked the motor mounts. I thought maybe the engine was shifting around under hard braking and on the hard turns. I can't make a educated evaluation on the condition of the mounts, because I don't know how they should look. They should be good enough though. I cant move the engine any considerable amount by hand. The engine idles very rough when cold, but becomes glass smooth when hot. I also checked the rear trans mount, because I thought I felt something similar when it shifted gears once. The rubber is soft, but I can't imagine the engine and trans moving that much. I could hardly move the trans by pushing + pulling on the driveshaft.

The best way for me to describe the sound would be comparing it to the feeling when hitting the bump stops on the suspension. Its a solid, sharp clunk. Almost as though someone wacked the floor board with a hammer.

[t walgamuth]

like bad motor mounts to me. or could be a broken or missing bolt holding them down. i had a mysterious clunk and eventuallly found a broken off bolt that held the motor mount to the sub frame and under braking the mount would rotate and make a big clunk noise.

i thought for sure it was a worn front suspension part.

tom w

[babymog]

If it does it when lightly bouncing the front end, it is probably dry ball-joints.

- Jeff Miller
190DT

[mbzkid]

Originally Posted by babymog

If it does it when lightly bouncing the front end, it is probably dry ball-joints.

- Jeff Miller

190DT

Do you mean doing a "shock test"? It didn't make any loud noises.

I forgot to mention that it only pops once in a while. I can't always casue the car to pop.

Also, it isn't a "pop pop pop" or anything repetitive. It's just one pop. I'm going to check the mounting bolts for the motor mounts.


EDIT: Motor mounts and associated hardware seem fine.

[babymog]

Then you might want to check the sway-bar bushings also.

- Jeff Miller
190DT

[mbzkid]

Originally Posted by babymog

Then you might want to check the sway-bar bushings also.

- Jeff Miller
190DT

Everything feels tight. I will look again though.

I just noticed the rear engine mount..."thing" is like jello. It couldn't be doing anything useful at this point. I believe its called a vibration dampner. Its between the oil pan and the front crossmember. Strangely, my 300D does not have this part.

[t walgamuth]

there is a mount there on a 240. we discovered it when we put the 300 motor in it. the guys didnt remove that from the crossmember and boy did it vibrate!

i have never heard what happens when the rubber part goes jelloey on you. i doubt very many folks are aware of it as it is pretty impossible to see.

tom w

[iNeon]

Originally Posted by t walgamuth

there is a mount there on a 240. we discovered it when we put the 300 motor in it. the guys didnt remove that from the crossmember and boy did it vibrate!

tom w

is this the t shaped mount with the little "tail" part? ot whe engine shock itself?

[t walgamuth]

that goes straight forward into a pocket in the back of the lower oil pan from the engine crossmember. nothing to do with the engine shock.

tom w

[mbzkid]

Originally Posted by t walgamuth

that goes straight forward into a pocket in the back of the lower oil pan from the engine crossmember. nothing to do with the engine shock.
tom w

Yes.


Its so mangled and soaked in oil, that I can't tell what it once looked like. I can't find the part on FastLane or MBZ.org either.

[t walgamuth]

never heard of anyone changing one. as i said most folks dont know they exist. i have owned prbly 12 240s and never would have known except for the fact we put the 300 engine in one and it vibrated like crazy.

i am sure you can get one from the factory. prob $6.

tom w

[mbzkid]

I wonder if that mount is causing the clunk.

[t walgamuth]

but did you check the main motor mounts? they seem more likely to me.

tom w

[mbzkid]

Originally Posted by t walgamuth

but did you check the main motor mounts? they seem more likely to me.

tom w

I rocked the engine by hand, and also inspected the motor mounts to the best of my ability. I would say they are fine. Its difficult to tell though because the mounts are hidden under the shields. I know for a fact that the engine mounts were replaced sometime around the early 90s. The car has quite a few miles on it though (odometer stopped at 160k).

The engine shock is not loose.

[t walgamuth]

the small cap screws on the motor mounts that attach the mount to the sub frame. they can be broken or stripped out and doing nothing. if one is not holding the mount can rotate and the engine slide back and forth when under braking or acceleration.

tom w