Loud drumming noise in cabin

[johnbonds]

'82 240D 4sp, 200k daily driver, owned since 1986:

Rebuilt USA started solenoid failed after 10mo. service, and it was a replacement for another which failed before that. I didn't want to do yet another starter change during exam week--so took it to a well-respected local indy (StarMotor in Charleston SC). I specified a new Bosch starter. In the process of installation, they found the alternator bolts loose, so fixed that. Then another call, reporting the motor mounts needed replacement. I was a bit puzzled by that, as they had been replaced incident to clutch replacement in Aug 07; but authorized them to go ahead. I retrieved the car on a Saturday after I turned in my grades (they left it outside with the keys inside the car--I brought the other key...). When the car started (nicely), there was an incredible thrumming or drumming sound inside the cabin. Not like anything I'd ever heard before from the car, and a lot of vibration evident in the whole car (the hood pulsated). I got out of the car to listen, opened the hood, but the noise outside was quite normal for a cold diesel. Back inside it still sounded like a agricultural vehicle. I drove it home. At speed, it is much better but still quite noisy.
When the engine warms up, the noise diminishes a bit--but it still well above normal in the cabin.

So I took it back the next week. They put it in the shop, returned it, saying they had neglected to refasten the exhaust pipe bracket properly and had put on a new one, as the engine was "now higher than it had been with the old motor mounts." This was now Christmas week. It sounded a bit better, but not much. I took it home. Again, it diminishes at highway speeds, but is still very noisy inside.

Off for the holidays, leaving the car in the garage. After a week, started it and it was as bad as it had been that first (cold) day. So, I've been reading in the books. I think it may be possible that the shop put in motor mounts for a 617 rather than a 616 engine, which would account for the rise in engine height in the car. But more likely, the engine shock absorber (if it was fitted) or the engine stop was damaged or not reinstalled correctly when the motor mounts were installed.

I'm sure this has happened to someone else here. Can you provide some wisdom? How do you suggest I approach the repair shop? I don't want to fix this myself, as I don't have a hoist and just don't want to do the work that I've already paid for ($1200 total for that starter and motormounts).

John Bonds: Charleston

[Codifex Maximus]

Hmm... replaced motor mounts and now there is a drumming noise.
Replacing those mounts changed the alignment of the engine.

I would definitely check the exhaust for leaks and the other mounts further back in the drive train. There may some parts drumming the underside of the vehicle at idle that don't sound as bad at speed.

Most of these items are trivial to service (and a whole lot easier to see) once you get the car sufficiently off the ground.

[JimSmith]

John,

If the noise is only perceptibly louder in the cabin, and, it would seem from your description of having the car idling with the hood up, the condition is apparent with the car not moving down the road, you have a sound short. If the engine is higher than it was before, it is feasible that the mounts are incorrect. In that case the short is likely the transmission mount or "engine stop."

I have changed the engine mounts on these cars several times. They typically last more than three years. When you change the engine mounts it is within the range of normal expectations to change the "engine stop" as well. This is a simple item at the rear of the engine. These things turn to goo if you have an oil leak or get them soaked in Diesel. Changing the engine mounts without removing this item will cause the rubber element to be extruded out of the mount as the engine is lifted to make room to remove the old mounts and insert the new mounts. Which will leave you with the likelihood of a metal to metal sound short from the engine to the cabin.

Take it back to the guy and tell him to lift it up on the hoist and go look at the condition of this part. Then, if the rubber is gone make it clear they owe you a new one since they were too ignorant to remove the old one before raising the engine.

And, a 240D has no engine shock. So there should not be one installed. If there is, I would be amazed since there is no provision to install one to my knowledge.

Good luck, and I hope this helps.

Jim

PS: If the noise changes at speed it is because, as you load the engine it rocks over slightly, which will either load or unload the contact point of the sound short. In your case it appears to unload the sound short.

[johnbonds]

Thanks for the help. I'll get on it next week, and will advise outcome.

Happy New Year!

JB

[leathermang]

Originally Posted by JimSmith

And, a 240D has no engine shock. So there should not be one installed. If there is, I would be amazed since there is no provision to install one to my knowledge. Jim

Whoops.. not often JimSmith misses something...
Some 240d's do have engine shocks..
AND if they have a particular transmission ( forget which , manual or auto ) they also have the place to retro fit them...
Straight from the FSM...
Greg

[fruitcakesa]

Originally Posted by leathermang

Whoops.. not often JimSmith misses something...
Some 240d's do have engine shocks..
AND if they have a particular transmission ( forget which , manual or auto ) they also have the place to retro fit them...
Straight from the FSM...
Greg

x2, I put one on my car

[JimSmith]

Originally Posted by leathermang

Whoops.. not often JimSmith misses something...
Some 240d's do have engine shocks..
AND if they have a particular transmission ( forget which , manual or auto ) they also have the place to retro fit them...
Straight from the FSM...
Greg

Well, you learn something everyday. I have had three 240D's and all were manual transmission equipped cars and none of them have had an engine shock absorber. I have never seen any extra mounting hardware on the engine or the adjacent body/frame. Interesting though. Jim

Edit: My manual, covering "Engines 615-617" which includes 616, makes no bones about the fact that only the 617 engine has a shock absorber. It is on the right side and goes between the engine support strut and the bracket for the lower control arm. My manual covers the W115 and W123 chassis. Maybe later in the W123 production run some pussified owners of 616's complained about vibration and asked for a shock absorber to be up to date with the 617 engines? At any rate it seems to be an afterthought that never made it into any 240D I owned.

Jim

[johnbonds]

I have a FSM vintage 1982. It sez (p 00.4-240/4) under job 00-240 (Removal and installation of engine shock absorber), sub-paragraph C (Engines 615, 616 in type 123.1), "Note: Models with automatic transmissions have an engine shock absorber (arrow) located between engine bearer and crossmember at left-hand side in straight ahead direction. The engine shock absorber was introduced subsequent to the beginning of the series.

Previously manufactured models which are brought in on account of vibrations (stuttering) can be retrofitted with the shock absorber (00-241 [job number])

This does NOT apply to models with manual transmissions."

Because that last cautionary note is separated by a line space, I think that means that this statement applies to the whole paragraph and not just to the retrofitting statement. But that's a guess.

The 4sp 240D does have an "engine stop" which is described in job 00-215 (Removal and installation of front engine stop) Subparagraph B. (Type 123.1) has this note: "Engine model 617 with two engine shock absorbers does not have the engine stop." (page 00.4-215/3)

Job 00-220, Adjustment of engine stop, repeats the note: "Types 123.105/130/132/150/190 with two engine shock absorbers do not have front engine stops." (p 00.4-220.3)

I'm going to double check the motor mount part numbers, and that front engine stop health.

Cheers,
jb

[JimSmith]

Thanks, John. The "need" for the shock absorber is tied to the automatic I see. I believe you have a 4 speed? So there should be no shock absorber on yours either.

Jim

[johnbonds]

On the third return, the shop discovered that the "belly pan" that protects the oil pan was "grounded" to the crossmember. The took it off, bent it a bit and reinstalled. Solved the problem. I have no idea how that got to be bent up--as it wasn't that way when the car went into the shop. They say they checked the front engine stop, and it was okay. Anyway, the noise is gone now. One of the old lessons in troubleshooting--check the easy things first! Neither the shop nor I did that. By the way, this is my last trip to this indy. His shop rate is now $105/hr. Amazing.

John Bonds, '82 240D 4sp, daily driver, 200k.
Charleston SC

[stimpy451]

You have Don Brewer, the bong-rattling drummer of Grand Funk Railroad, in your back seat. Turn around slowly so you don't scare him off.

[Codifex Maximus]

Originally Posted by johnbonds

On the third return, the shop discovered that the "belly pan" that protects the oil pan was "grounded" to the crossmember. The took it off, bent it a bit and reinstalled. Solved the problem. I have no idea how that got to be bent up--as it wasn't that way when the car went into the shop. They say they checked the front engine stop, and it was okay. Anyway, the noise is gone now. One of the old lessons in troubleshooting--check the easy things first! Neither the shop nor I did that. By the way, this is my last trip to this indy. His shop rate is now $105/hr. Amazing.

John Bonds, '82 240D 4sp, daily driver, 200k.
Charleston SC

Congrats on getting rid of the rattling!

Ouchies! $105/hr.

[charmalu]

$105.00/hr is cheap. my indy (use to use) is up to $117.00/hr

Everytime I work on the car, I should put that much in the bank ea hr
worked on it.
I`ll be rich in no time .

good you got the problem fixed. It`s always the little things that get you.

Charlie