GAH ! - PeachParts Mercedes-Benz Forum

vwnate1 · #1 12-26-2022, 06:05 PM

My guy called today and says a connecting rod let go and broke the cylinder block .

Now I have to see what's what with the engine Rich offered .

Stand by .

JHZR2 · #2 12-26-2022, 08:06 PM

Quote:

Originally Posted by vwnate1

My guy called today and says a connecting rod let go and broke the cylinder block .

Now I have to see what's what with the engine Rich offered .

Stand by .

So, what’s the typical root cause of this? A bad bearing that then beats the rod mounting points into oblivion until it breaks? I can’t imagine it broke the rod.

ROLLGUY · #3 12-26-2022, 09:15 PM

Quote:

Originally Posted by JHZR2

So, what’s the typical root cause of this? A bad bearing that then beats the rod mounting points into oblivion until it breaks? I can’t imagine it broke the rod.

These engines are so robust, that they usually give you early warning of impending doom. A rod knock almost always is the first indication of a problem. If an oil cooler hose fails, all the oil will get pumped out in short order, but even then, an engine can be repaired if shut down soon enough. A rod through the block is very rare with one of these engines.

vwnate1 · #4 12-26-2022, 09:37 PM

That's a very good question ~ I've had some older European engines that were *so* close inside the block that a loose rod would hit the case and break hole(s) in it .

I find it hard to believe Mercedes would allow such design .

Once I get the engine out and apart I'll know what's what .

Occasionally after many years a connecting rod bolt will come loose, back out and drop, then it's just a matter of the perfect storm of load & RPM's before the other bolt lets go or gets lose and allows the rod's big end to come off the crank where it's often knocked aside and through the block's wall .

I don't have any interest in making this into a 5 cylinder car .

Indeed 40,000 miles is a very short length of engine life .

It didn;t smoke nor drip and always started in less than one revolution .

Sigh .

ykobayashi · #5 12-27-2022, 01:45 AM

Sorry to hear the bad news. Wow. Your car ran really well. I’m stunned the rod let go like that.

vwnate1 · #6 12-27-2022, 02:12 AM

Yes, it did .

Too bad you never joined me on my road rallies, it's amazing how well a 40 year old 57 HP Diesel taxi comported itself .

It will rise and live again ! .

I'll prolly have to go deep in hock to get it done but I do not want a newer car.

vwnate1 · #7 01-08-2023, 12:18 PM

Okay, it turns out the connecting rod that let go punched a hole in the left side of the cylinder block right behind the A/C compressor mount bracket .

Rollguy of this very forum has a ready to go block that's been cleaned and hon ed, yesterday my son and big brother loaded the car onto a tow dolly and dragged it up there, we'll see what transpires .

I've seen his finished work, he's detail oriented like me so I'm sure this will be a good final repair .

I'd like to have a STD./STD. crankshaft in it and he has some old OM616 engines he thinks will have one .

This engine has a bit more than 40,000 miles since major overhaul so I hope the cylinder head will still be good along with the rebuilt IP, fuel injectors and factory water pump .

I'm pretty sure the oil pan is dented, whatever he says it needs I'll go get, I'm already buried into this car having owned it for over twenty years and 200,000 + miles, might as well go the whole hog .

Stand by .

ROLLGUY · #8 01-16-2023, 04:31 PM

With very little detective work, I found the "smoking gun". The rod "windowed" the block because a connecting rod nut was NOT tightened properly. This is not the original engine, it was rebuilt some time ago (Nate knows). One rod bolt was sheared off, and the other remains intact with the nut missing. I will probably find it amongst the hundred or so broken pieces of piston in the pan (have not looked yet). Stay tuned.......

chasinthesun · #9 01-16-2023, 09:32 PM

Their were 2 616 motors for sale on cl here in Houston ,cheap too , not sure if running , in the parts section