Hello-

I've got an 83' 240 that has an aweful engine knock. I checked to see if it was the injectors by cracking the lines and it still knocks like crazy. It continues to knock the more you rev it up to the point where it sounds like it may just let something loose. I'm assuming the worst-bad rod/bearings or damaged piston. What am i looking at here as far as repair or replacement of the engine, assuming I do the work myself? Where and for how much can I find a used but good 240D motor? Thanks!

Looks like a bottom end failure, usually the OM 616 has bullet proof cranks, seen them easily last over 500,000 miles with average maintenance. If all you need is bearings, it wouldn't cost you much but it looks like this car has seen some real poor times for the crank to fail.

These are easy engines to rebuild. I have a spare crank and cam for a 240D in the garage if you end up needing one. Even with new pistons (and you supplying the labor) a rebuild should not cost more than around $2k.

__________________
Jim

mdlwolf,

Don't run the engine any more or you may damage the crank beyond repair.

Pull the pan and investigate to find out what is wrong with the engine.

P E H

'77 sounded a lot like a rod. I'm currently replacing balancer and pulley assembly as PO goofed up when he had it fixed last time it came loose. Loosen up(better still-remove) all of the belts and listen....

__________________
Jim

'49 170?(donated to church in Darmstadt '58)
'58 220S(crusher, after '73 fire[San Antonio])
'72 280SE 4.5
'77 240D
'81 300SD
'83 240D parts car

does it knock on decel and accel?
knock at neutral power load?

knock at idle?

knock hot or cold? any difference?

this will help to guess a diagnosis better..

__________________

79 240D my current toy
42 years a Diesel addict

240D sold
250SE sold
220D sold
280C sold
280S sold
300D (2) sold
300CD sold
300DT sold
300SD sold
380SL sold

It doesn't knock much at idle. When it revs up it really begins to knock and the knock doesn't stop till it comes to an idle. The faster you go the louder the knock seems to get. I'm going to pull the pan next week and see what's up. If it needs new bearings do I need to pull the motor?

Engatwork-Thanks, I'll let you know if I'll need those.

Lastly, I searched the net for a used motor and on car-parts.com there are allot of places selling them for $800-1000. Would this be something to consider?

Thanks!

If it is a bearing problem (doesnt sound like one in your description) it would need more than a bearing, the crank
would have issues too.. you did not say if it is louder cold or hot, accel or decell???

You could have an accesory making that noise or something else... Track the noise by using a small piece of garden hose to your ear...
keep us posted

__________________

79 240D my current toy
42 years a Diesel addict

240D sold
250SE sold
220D sold
280C sold
280S sold
300D (2) sold
300CD sold
300DT sold
300SD sold
380SL sold

The knock doesn't seem to get much louder the more you accelerate. Once it starts it's volume seems to stay the same. It begins just above idle and seems to follow the revs of the motor, as in, as the rpm's raise the intervals between each knock gets shorter. It seems to follow a consistent pattern with regard to engine speed. It also seems to be coming from the front of the engine, closest to the radiator but up around the valve cover. One thing I did notice is that when I cracked the injector lines 3 out four made a noticable difference in the idle speed. The one closest to the front of the motor didn't seem to change the idle? Anything else I should check before I pull the oil pan off? Thanks! Also, forgot to mention that the knock doesn't change with a cold or hot engine.

You will not be able to tell much about it by dropping your lower pan. I would tear it down and then determine whether to rebuild or find another one.

__________________
Jim

I wouldn't be looking at the lower end at all according to your description..
Get a small section of hoes and focus in on where it is coming from..
accesory item?

__________________

79 240D my current toy
42 years a Diesel addict

240D sold
250SE sold
220D sold
280C sold
280S sold
300D (2) sold
300CD sold
300DT sold
300SD sold
380SL sold

The knock seems to be coming from the upper area of the engine. Maybe from a piston? It has a very sharp, metallic consistent sound to it. It looks like I'm going to pull the motor. I'll need to get a hoist and an engine stand so I'm wondering what weight capacity I should be looking at? I found a place that has a complete engine with 130K on it that has been compression checked and has a 6 month warranty for $1k with exchange. What do you think?

What keeps bothering me is that as far as I know the motor in it now has only 129K on it and seems to have been well serviced. It had all german filters when I got it, not that it means anything? The car itself is clean and doesn't seem to have been abused? It fires right up with very minimal glow time. It doesn't smoke at all. I pulled the valve cover today and found the valves to be tight but no other issues in that region. The motor turns over smoothly by hand. I did notice that when line up the notch on the cam the pulley read to the left of the 0 marker at about 2.5-3. My 300D reads at 0 when I line up the notch. Does this mean anything?

Hey Mike,

First, let me say that I have never torn into one of these engines to learn more about them, so, my comments are based upon theory only:

If the knock it caused by a piston or a wrist pin or a connecting rod bearing for that matter, there should be some change in volume of the knock when you shut that cylinder off by disconnecting the fuel line.

When you did this, to each cylinder individually, was there no change in sound from any one of these four tests (four individual disconnects)?

If the sound is coming from the upper end of the engine, there should be some type of change in the sound if it is any way related to a specific cylinder.

If this test fails to produce any change in sound, I do not see how the noise could possibly be related to anything on the top of the engine.

How's my 123 doing??

Hi Brian-

Your 123 is doing very well. I just put over 6K miles on it driving from the east to west coast in a roundabout way. No major problems!

I'll double check each cylinder again. When I checked today each line that I cracked made the engine stumble but the knock seemed to persist. I'll try each one again and rev the motor this time to see if that makes any difference. Thanks for the advice.

I think you are over reacting with pulling and replacing the engine.. you need a diagnosis first..
If you replace the engine I would be interested in the old one..

__________________

79 240D my current toy
42 years a Diesel addict

240D sold
250SE sold
220D sold
280C sold
280S sold
300D (2) sold
300CD sold
300DT sold
300SD sold
380SL sold