Hi Guys,

1st post, in need of advice.

I have the knock of doom. The one everyone really never solves. The one that when you look it up on youtube, they say "thats normal, or I drive it like that, or I swapped the engine, or I threw all the parts at it, and it stopped"...

Before we go into all my findings, Im pretty sure its the number 2 wrist pin.

Main questions are: 1. Is this typical. 2. Does it mean more are going to happen. 3. Can I just change the one, and its gonna run another 200k.

Dont talk me into a 606 swap, Ill fckn do it, I swear!

Background. Car had been taken car of mechanically pretty well for as long as I can tell. I take care of it the same or better.

What I am not good at doing, is driving this thing softly. I was into it pretty good, and am most times, when I heard a "different" noise appear. Only drove it with the noise a few miles at as low as I could/side street rpms. Im not beating on it, but its driven at 36-4100 rpms for 20-50 mils at a time. I dont rev the piss out of it getting the the highway. Even though it shifts at 5100 if I let it!

Pre chambers are perfect. Injectors pop with in spec +/- 1850psi. Installed new pre chamber crushes and injector washers today.

Compression is: 1 320. 2 320. 3 360. 4 340. 5 340. appox 25o,xxx miles.

Cyl #2 has visible scoring on 1 part of the wall. Very minor, but its there. All other cylinder are clean, and crosshatched. Tops of pistons are clean/no pitting/heat damaged (this surprises me)

No bearing material in the pan.

Dropped the upper oil pan, and all rods are tight/not rocking.

Oil pressure is 20-25 at idle, 45-65 driving.

Noise can be audibly heard with a screwdriver to the ear at cylinder 2. Obviously it echo's throughout the engine, but it is definitely the loudest at cyl 2.


So... Back to my questions above. My concern is if I only change cyl 2, is it eventually going to happen to other cylinders. Meaning is this the beginning, and if I dont do em all, im doing it wrong.

Im happy its cyl 2, cause it means I dont have to pull the engine.


Personally, I would rather take the time to do the OM606 swap, than do a fresh/full rebuild on this engine.

If its just pull the head, and 1 piston/bearing assembly, Im ok with that (also timing chains).

Happy to hear your suggestions.

Thanks.

Tom.

Also, Lashpads are all in good shape/no visible scoring or heat wear, top and bottom. Valves are adjusted to spec, now, and when I got the car, approx 30,xxx ago. Cam looks new. Cam pedestals are tight. Timing chain has good tension.

Thanks.

If, indeed, the source of the sound can be narrowed to one cylinder, and the big end bearing is OK, then the question may become: is it due to 1) piston clearance, 2) pin clearance in the piston, 3) pin clearance in the rod, or 4) a cracked piston.

Post a video of the sound...

__________________
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)

Does it knock at idle ? .

If so diagnosing the cylinder is dead easy and only requires a 17MM ATF wrench to loosen the injector pipes one at a time until the knocking stops or reduces .

If I could, I'd swap in an OM603 because they're torque monsters like all inline engines are .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Mine sounds like this https://www.youtube.com/watch?v=d0JBKGmPUb0
Sometimes without the air cleaner rattle, other times with it. I like how it rattles and always starts and runs.

Just got the 85TD back after the body shop did nothing. Car sat for a year and started right up the 1st time.

__________________
85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

Your engine isn't knocking, I hear it nail a couple times .

If you fix those rubber air cleaner mounts then jamb an old shock absorber bushing between the engine and air cleaner, it will not break .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

@ nate: I know. I posted link because some people thing that something is wrong with the engine worried about the "knocking" when it's only the beautiful 617 symphony.

Of course, I've had them say other things are "normal" when they are simply common because most of the old cars are worn. There is a problem with the Porsche 911 trans not going into 1st gear unless stopped. It's syncros and common, not normal.

I think of whether the owners back when the cars were new would have put up with whatever item is up for discussion. Porsche couldn't have won as many races as they did if the trans didn't work well when new.

Wealthy Mercedes drivers wouldn't have put up with hard shifting or flares or any of the other discussions on this board.

The OP is talking about the "knock of doom" and an engine swap but the only thing noted is very slight scoring on 1 cylinder wall at 250,000 mi and good oil pressure & compression. Seems like a drive it and forget it situation. He'll have new oil because he dropped the pan. Adjust the valves and forget it.

__________________
85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

Have you tried swapping the injector to another cylinder and see if it follows.

I lost count of all the tranny jobs I didn't have to do because the culprit was actually the bushing or bearing in the end of the crankshaft .

It's one of those niggly little things that needs periodic cleaning and lubrication but no one wants to pull the tranny just to do that....

Most shops would instead do a full clutch or tranny job and still neglect to clean and lube that part .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better