Catastrophic Engine Failure

[G$ 993]

Hello.  Hoping to draw on the experience of the forum to help me navigate a terrible problem which just happened to my 1970 280 SL.  This is a one family car and I have records going back over 30 years.  The car had been idle or used minimally for a number of years prior to my recent stewardship.  It had some deferred maintenance issues which I thought I had overcome.  The car did have a top end rebuild this April including an upgrade to a euro spec cam.   The previous cam was flat due to oil starvation secondary to a dent in the oil feeder tubing.   All new rockers, towers, cam, timing chain, etc were also utilized.  The work went great and the car ran excellent.   Since April, the only use the car has received is monthly 30 minutes start ups, the car had been idle until this week.  Probably less then 250 miles of driving since top end rebuild.  I took it back in for an oil change and valve adjustment.   I noticed that the car was running a little rough which I thought was a valve issue.  The work was completed at a reputable shop by a very experienced mechanic.  Anyway, after picking the car up, it sounded great at start up and on initial few minutes of driving.  While running on the HWY for just a couple of miles on the drive home, there was an escalation in engine noise and then a boom(!).  This occurred over about 15 seconds.  Direct inspection of the engine revealed a hole in the lower case and a puddle of oil on the ground.  So this appears to be a catastrophic engine failure.  I’m guessing its secondary to fluid in the piston and a subsequent thrown rod.  The shop was very responsive to the problem and had the car towed.  They are going to remove the engine and tear it down looking for the source.  They said they will even replace the engine if its their fault.  There was oil in the pan upon return to the shop and oil running through the top end perfectly when turning engine over.

Engine failure like this is a rare occurrence in MB cars.  Has anyone had a similar experience?  I have some basic mechanical knowledge and skill but likely not enough to really navigate this problem with ease.   Could the euro cam be part of the issue?  What should I be doing and watching out for as things unfold?  Help please!

Regards,
Mark

[GGR]

This happened to me on an Alfa Romeo GTV 2000 many years ago. Same story: I was driving on the highway and all of a sudden there was a noise going crescendo followed by a bang. Resuslt was a hole in the engine block and a nacked crankshaft journal I could see through the hole where a rod should have normally been. In my case the oil pressure was a bit weak and I guess lubrication was not enough for highway speed.

I don't think the camshaft has anything to do with your issue. I am surprised there is still oil running through the top end perfectly as pressure should be lost due to the thrown rod. I would definitely look at a lubrication issue. The oil pump can get disconnected and stop lubricating (happened to a member here recently).

If the shop is indeed reputable and is willing to do right, then let them report to you on what happened. You can share here and members will surely come with comments and advice. Pictures of the damage will help.

Good luck!

[ja17]

Check to see if the upper oil filter seal (in the  upper filter housing) is missing. If so, some debris may have by-passed the oil filter and blocked an oil passage in the crankshaft. Debris may have entered the engine during the top end rebuild. Possibly some scrapped off head gasket material.

[GGR]

True, That seal missing is a common occurrence, well documented on this board.

[GGR]

Now that I think of it, a blocked oil passage in the crankshaft may well explain how you have oil reaching the top end despite a thrown rod.

[G$ 993]

Thank you for the suggestions.  I am aware of the filter seal and actually ordered that part specifically to ensure it was done correctly during the last oil change and top end work. 

Is it reasonable to conclude that oil was in the cylinder as the puddle underneath the engine (where the hole is) was also oil?

I will update when I hear more.  If you have anymore ideas, please let me know so I can make sure everything is covered.

[Benz Dr.]

A chain is as strong as its weakest link.

  I bet the head rebuild caused this. One or more rod bearings were worn just enough that the extra compression made it/them fail. Most of the time you can rebuild your cylinder head and everything will be OK. I kind of gauge if the bottom end should come apart by how much wear I see in the cylinders but that's hardly an exact science.
Looking at overall general wear, if the rockers and ball studs are worn, the valve guides are worn, oil pressure drops at idle, cam gear is worn, then the bearings will be too.

Very big of your shop to offer free repairs but I doubt very much that they did much wrong. If the head is defective that may be their fault but stuff they never touched............. well, just saying. 

[ja17]

How  has your oil pressure been?  If you had a new upper seal in the filter housing then the problem is probably not blockage.

[G$ 993]

Oil pressure good.

[Benz Dr.]

Just so I get the story right; there was still lots of oil in the oil pan when your car was returned to the shop? Turning the engine over with the starter produced good oil flow at the oil feed tube?
How is it that they were able to spin the engine over with a broken connecting rod? Which side of the engine has the hole where the rod came out? I've seen engines that failed because they ran out of oil and in that case the connecting rod became welded to the crank shaft and the rod snapped in two. The engine wasn't running at high speed when it broke because the engine was about to seize up. Although the crank, rod and piston were damaged, the rest of the engine was salvaged and there was no hole in the block.
A broken rod at higher engine speed would likely cause more damage so a hole may not be unexpected. Why do you think oil in the cylinder caused this to happen? I've seen engines hydro lock and all it did was bend the connecting rod.

I agree that pics would be helpful.   

[GGR]

What I don't really understand is how can the engine get oil flowing in the top end at cranking speed with a thrown rod. Oil pressure loss at crankshaft level would lower drastically oil flowing towards the top end. Unless there is a blockage somewhere which would explain throwing a rod. Or unless we assume wrongly the engine threw a rod. But what else could cause a hole in the block? I guess we need more info on the engine's condition.

[stickandrudderman]

That engine has been penetrated by a member........................

[G$ 993]

Just so  get the story right; there was still lots of oil in the oil pan when your car was returned to the shop? Turning the engine over with the starter produced good oil flow at the oil feed tube?
Who is it that they were able to spin the engine over with a broken connecting rod? Which side of the engine has the hole where the rod came out? I've seen engines that failed because they ran out of oil and in that case the connecting rod became welded to the crank shaft and the rod snapped in two. The engine wasn't running at high speed when it broke because the engine was about to seize up. Although the crank, rod and piston was damaged, the res of the engine was salvaged and there was no hole in the block.
A broken rod at higher engine speed would likely cause more damage so a hole may not be unexpected. Why do you think oil in the cylinder caused this to happen? I've seen engines hydro lock and all it did was bend the connecting rod.

Yes there was oil in the pan and exiting the feeder tube while turning it over.  There was oil pressure noted on the gauge as well.  The hole is in the passenger side of the block near the front above the pan. 

I was driving on the HWY when this happened traveling about 60 mph.

I certainly agree that it does not all make sense. 

Yes pics would be helpful.  I will see what I can do.

[G$ 993]

So the problem seems to be that the bearing between the connecting rod and the drive shaft failed which cause the piston to seize and the connecting rod to break.  This occurred on the #2 cylinder.  The engine was able to turn over because the bottom portion of the rod which connected to the crank was completely gone.  Mechanic is unsure why this happened.  Everything else appears fine.  Valves look good.  Oil feeder to cylinder open.  Lubrication appeared satisfactory.   There was a small fire involving the wiring coming from battery and to the alternator.  Ideas?  Struggling to get pics uploaded but will keep trying.

[G$ 993]

Link to pics.  Ignore SAAB pics please:

https://www.flickr.com/photos/85090564@N05/

[Jonny B]

OMG - Picture 7270 sure tells a sad tail!

[G$ 993]

Bump for ideas

[GGR]

At that point your best bet is to locate a good 280SE short block. Others will confirm if US models had a lower compression ratio at some point or not. You should still have your mechanic determine the cause of the failure as you don't want the same mistake to be repeated when putting the other engine together.

[Benz Dr.]

I stand with what I said in post number 6. Number 2 rod bearing was worn enough that it fell apart with the extra compression after the cylinder head rebuild.

Compression ratios are generally found within the cylinder head and not the block. You can increase compression by decking the block and only slightly by boring to a larger size piston.

[tel76]

I cannot agree with the number two rod bearing being worn that it fell apart with extra compression.
If the bearing has failed due to lack of oil pressure there would have been some warning, ie knocking for a short period of time, but the driver was not operating at high revs when the damaged occurred.
What is the condition of the other five big end bearings? Also what is the condition of the adjacent main bearing, if the main bearing failed and turned it would block off the oil supply to number two rod bearing.
Do we have a picture of the failed item both con-rod and shells?
In post #13 you state "the connecting rod and driveshaft (crankshaft) failed which caused the piston to seize and the rod to break"  in your pictures the piston shows no sign of seizure.
Was the big end securing nuts tight and in good condition?

[Benz Dr.]

I cannot agree with the number two rod bearing being worn that it fell apart with extra compression.
If the bearing has failed due to lack of oil pressure there would have been some warning, ie knocking for a short period of time, but the driver was not operating at high revs when the damaged occurred.
What is the condition of the other five big end bearings? Also what is the condition of the adjacent main bearing, if the main bearing failed and turned it would block off the oil supply to number two rod bearing.
Do we have a picture of the failed item both con-rod and shells?
In post #13 you state "the connecting rod and driveshaft (crankshaft) failed which caused the piston to seize and the rod to break"  in your pictures the piston shows no sign of seizure.
Was the big end securing nuts tight and in good condition?

How exactly do you propose to determine if the connecting rod nuts were tight? There's nothing left of the connecting rod. 

Do you really think that a main bearing could turn that easily? It appears that there was sufficient oil pressure as the cam looks good, and as you noted, the removed piston, although badly smashed, had lots of oil going to it. All of the other visible cylinders show no signs of scoring that would indicate lack of oil or oil pressure. A main bearing would turn in the block only if the crank journal seized to it but there appears to be no indication of anything like that happening. Of course, without having said engine in front of us some things remain unknown.

I've seen where an engine failed shortly after a cylinder head rebuild. One shift over 4,500 RPM is all it took. All you need is one worn rod bearing and the extra load of improved compression will finally take it out. This bearing would have failed eventually over time. Since there appears to be minimal cylinder wear one would assume the bottom end would be OK so there is a small possibility that a connecting rod nut wasn't tightened correctly. If that is the case, then the head rebuild only ensured its demise.



 

[tel76]

There must have been something left of the lower part of the connecting rod, it cannot just disappear.
The only time a main bearing can turn is if there is a loss of oil pressure to that bearing and the bearing will seize and the shell could turn.
An inspection of the oil relief valve may throw up some clues, especially as the work done on the oil filter seals could be suspect ie did any of the discarded rubber make its way into the oil galleries?
The camshaft will look good as it takes a considerable time for this item to show any sign of distress after an oil pressure failure and the driver says the failure happened very quickly into his drive.
As you say without being present at the strip down we will never really know.
I hope that all those people who carry out the so called Italian tune up will look at the pictures.

[stickandrudderman]

Reply Reply with quote 


There must have been something left of the lower part of the connecting rod, it cannot just disappear.

Perhaps it left through the hole in the block?

I find it unlikely that some human error on the part of the people that did the head could cause this failure; it was an event waiting to happen and the increased workload generated by the newly efficient cylinder head was probably enough to convince the bearing to make a bid for freedom.

[G$ 993]

Thank you all for the comments.  Obviously there remain unanswered questions.  Sounds like an uncommon issue.

I cannot agree with the number two rod bearing being worn that it fell apart with extra compression.
If the bearing has failed due to lack of oil pressure there would have been some warning, ie knocking for a short period of time, but the driver was not operating at high revs when the damaged occurred.
What is the condition of the other five big end bearings? Also what is the condition of the adjacent main bearing, if the main bearing failed and turned it would block off the oil supply to number two rod bearing.
Do we have a picture of the failed item both con-rod and shells?
In post #13 you state "the connecting rod and driveshaft (crankshaft) failed which caused the piston to seize and the rod to break"  in your pictures the piston shows no sign of seizure.
Was the big end securing nuts tight and in good condition?

I don't know the condition of the other bearings or connecting rods.  They had not been disassembled. 

You are correct, the piston looks ok.  Can't explain this.

I don't know the condition of the securing nuts as the lower portion of the rod was gone having exited through the side of the block.  Shards of the bearing were noted in the engine pan.

At that point your best bet is to locate a good 280SE short block. Others will confirm if US models had a lower compression ratio at some point or not. You should still have your mechanic determine the cause of the failure as you don't want the same mistake to be repeated when putting the other engine together.

I agree. 

[tel76]

I find it very interesting that the lower half of the con-rod has disappeared through the crankcase hole, this suggests that the bolts or nuts have failed, usually when a con-rod breaks like this the lower part is left bolted to the crankshaft.
Are you going to investigate this further, you need to know why this happened.