i was doing 65mph/110km/h down the highway when a terrible knocking sound started.

pulled over got a friend to come with a trailer and rescue my girl and I.

7 months of bit by bit



https://www.youtube.com/watch?v=nhuQjDkNN5o



then i reassembled....


I changed all fluids and done a valve adjustment ( it didn't need one as i checked each valve and it was perfect it had done 150km since i done it the day the knock started )

and yeah.


this was today....



https://www.youtube.com/watch?v=tl32ICupQF0

That's an internal knock. Connecting rod or main bearing, the dull "thud" of the noise pushes me towards main bearing rather than rod. You can definitively rule out injection problems since the noise never stopped when you cracked all 5 injectors. The prechamber you suspect is bad probably isn't, it looked like the injector was just weeping diesel on it from a hard line that wasn't tight enough or injector half leaking.

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Current stable:
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:/ the engine was rebuilt 70,000km ago, 45,000 miles


i checked the rods, didn't check the main bearings though. unsure how to tell if they are bad ?

Pull the caps and inspect the shells visually. Use plastigauge to check clearances if you can't tell by looking. With a knock like you have in the video you gave, I'd expect you can tell by looking who's at fault.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Thank you.


today i did a quick test and thought to video it of the " oil pressure check" to make sure my oil pump was still good.


https://www.youtube.com/watch?v=GMRCvmyTlOk


i'll pull the engine out over the next couple of days and take a look.

On the second video, at the 1:45 mark when you say "pre chamber might be bad..." it looks like there is something coming from around the the pre chamber collar. I can't say for sure if it is a video artifact or if there really is compression escaping the pre chamber. I'm just mentioning this because of the recent video series where Kent found a broken combustion pre chamber on one of his cars. (see this video https://www.youtube.com/watch?v=JGfIyPwCMRQ). The end result of this broken pre chamber was a bent connecting rod.
Maybe it's worth removing the injector and see if the pre chamber is intact before taking the oil pan off again?

Don't get carried away with the prechamber. The knocking doesn't stop when he cracks the injector, so it is NOT an injection or compression noise.

There's also fuel dripped all over the area. If the head is hot, the fuel will vaporize and shows up as bubbles in the puddle. It's easy to think it's a compression leak when it's nothing more than fuel vaporization.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Everything is pointing to conrod.

The prechamber though, i believe the seal between prechamber and engine block has worn away. That's a side issue that will be addressed

Just to be clear

If I may make a suggestion, if you are going to go deep enough into it to check connecting rod bearings and main rod bearings, I would plastigauge ALL of them and replace as needed. Might need to get the crank re-ground and go oversize on all main and con-rod bearings to fix it properly. In all actuality if the engine was rebuilt a short time ago, they all should be good but obviously this may not the case based on the knock.

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I would inspect the cylinder for dropped prechamber pieces. Do you have a borescope handy?

just bought one.

Have yet to take the engine out of the car again. It's a bit of a job as i have to push/drag the engine on the stand over grass to get it into the little back shed and well, under the weight of the engine the wheels of the crane become a plough....

Buy four 2x6 and make a plank trail.