Pagoda SL Group
W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: G$ 993 on August 13, 2015, 04:19:09
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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
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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!
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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.
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True, That seal missing is a common occurrence, well documented on this board.
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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.
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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.
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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. :)
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How has your oil pressure been? If you had a new upper seal in the filter housing then the problem is probably not blockage.
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Oil pressure good.
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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.
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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.
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That engine has been penetrated by a member........................ ;)
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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.
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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.
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Link to pics. Ignore SAAB pics please:
https://www.flickr.com/photos/85090564@N05/
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OMG - Picture 7270 sure tells a sad tail!
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Bump for ideas
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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.
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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.
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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?
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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.
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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.
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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.
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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.
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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.
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I've seen a couple of engines that let go in this fashion and none of the connecting rods were left attached to the crank. However, none of them came out through the side of the block like this engine did. :o In every case, the connecting rod came apart at the parting surface of the rod cap. I suspect that the rod bolts, while very strong, will break when pushed beyond their normal load limits when the sudden shock breaks them in two.
As hard as it might seem to be able to believe, extra compression from rebuilding a cylinder head can and will make a rod bearing fail. If everything is in good nick, then you won't have a problem. A bit too much bearing clearance and it can fail quickly.
It happened to me in a 220SEb Coupe once after a head rebuild. I made one shift over 4K and it started to make a soft noise. Since I was in the middle of nowhere in a torrential rain storm, and this was long before cell phones, I limped along the side of the road until I got closer to help with an ever increasing knock . The crank was toast anyway and with the engine full of metal shards there wasn't much to save. :'( This was in 1988 so it was a while ago.
Most of the time a fresh cylinder head will bring your engine back to life but every once in a while it can also kill it. This is, unfortunately, one of those uncommon times. :(
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I've seen a couple of engines that let go in this fashion and none of the connecting rods were left attached to the crank. However, none of them came out through the side of the block like this engine did. :o In every case, the connecting rod came apart at the parting surface of the rod cap. I suspect that the rod bolts, while very strong, will break when pushed beyond their normal load limits when the sudden shock breaks them in two.
As hard as it might seem to be able to believe, extra compression from rebuilding a cylinder head can and will make a rod bearing fail. If everything is in good nick, then you won't have a problem. A bit too much bearing clearance and it can fail quickly.
It happened to me in a 220SEb Coupe once after a head rebuild. I made one shift over 4K and it started to make a soft noise. Since I was in the middle of nowhere in a torrential rain storm, and this was long before cell phones, I limped along the side of the road until I got closer to help with an ever increasing knock . The crank was toast anyway and with the engine full of metal shards there wasn't much to save. :'( This was in 1988 so it was a while ago.
Most of the time a fresh cylinder head will bring your engine back to life but every once in a while it can also kill it. This is, unfortunately, one of those uncommon times. :(
Great post. Thank you!
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Does this engine number look like a factory stamp? The shop is suggesting that it may not be a factory stamp and that the block may be unoriginal. The number does match. I have detailed records on the car back to 1980 with no indication of rebuild or accident. Thoughts?
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The number does look less 'clean' than the ones I am used to seeing on factory original blocks, more like what a garage might have stamped into a replacement block, so I can see where the shop is coming from.
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The stamps that MB used tend to be somewhat larger than what is being used today. This is not an original stamping but none of this matters in my opinion. When people start paying 50K more for a numbers matching car at auction then it will.
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Thanks for the comments. This helps confirm that the engine is not original and may have had a poor build at some point. Turns out the main bearing slipped which blocked oil to the #2 cylinder causing the failure. :(
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Interesting findings. Did it turn or move before this happened or after? My main question has to be, why did it turn? I've seen where a main bearing was installed upside down - maybe this is what happened? It's pretty hard for the bearing to turn under normal running conditions unless it's run dry.
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For reference here is the stamp on my block. I have heard of Mercedes dealers stamping factory replacement engines with the serial number of the old engine. I assume this is what was done with your car. It bothers me that we are now seeing the term "Numbers Matching" becoming important in the world of European cars. What was once a way to verify that the particular high performance engine was correct and was the supplied type of engine on American muscle cars (where there were several engine options) has now filtered down to European cars where there is usually only one available engine doesn't make sense. Of course you will have strong opinions on both sides of the aisle usually delineated along the lines of who has and who doesn't have a matching numbers engine.
I guess the "Good" news is you didn't destroy the original "Numbers Matching" engine.
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Weren't factory replacement engines' blocks pailted red? Or am i confusing with another make?
Rgarding matching numbers, it has always been a big deal on Jaguars, which are european cars. Not so much on Mercedes, go figure why.
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No Jag experience so thanks for the info. Porsche cars have only recently starting getting into the Numbers Matching game. There is actually a hierarchy where numbers matching has a certain value. Below that a correct date factory replacement unstamped block (can't just grind off the serial number as the block isn't machined where the serial number is.) and finally a miss-matched numbers block.
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Use the overall search function and type in "engine block color" limit the search to "search in topic subjects" and you will get three hits. These give a pretty good explanation of the underlying red on the engine block. When installed the block should be black.
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Interesting findings. Did it turn or move before this happened or after? My main question has to be, why did it turn? I've seen where a main bearing was installed upside down - maybe this is what happened? It's pretty hard for the bearing to turn under normal running conditions unless it's run dry.
From my shop: "The crankshaft bearings have been replaced and the main bearings are showing some uneven edge wear which is not typical. A more extensive tear down and complete measurement of the old engine assembly may reveal more findings pertaining to the previous workmanship done on the block and crankshaft."
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Wanted to give a brief thread update. The car is now at Motoring Investments (these guys are awesome) for a full rebuild with a new block! The old engine is now out and the engine bay and underside of the car will be getting a full pressure clean. I'll update the thread periodically as the build proceeds.
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Thanks for this and future updates, it's always nice to see how a story gets concluded. You're getting it done right, that's for sure!
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Engine build update!
The build will also include full cosmetics
The “new” SE block has been disassembled. The taper is “zero” and wear is minimal. 87.0mm pistons have been ordered. The crankshaft from the old engine looks excellent. The aluminum parts (intake manifold, oil filter assembly, etc.) have been sent out for cleaning, aka tumbling. The fuel injection pump has been sent out for mechanical overhaul and cosmetic restoration. The oil pump is also in excellent condition.
Note the light surface rust in the engine bay. Pics show the bay after power washing and after being prepped for paint.
The undercarriage is in excellent original shape. The car does need a full new exhaust and suspension refresh.
Pics for your viewing pleasure.
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More pics
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Whilst you have the engine out you may want to consider having the engine bay repainted, its something that you won’t regret and will never be cheaper than now without engine etc.
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Two things:
1 ) any engine that spit/s out a rod bearing/s has a very good chance that the crank will be bent. I would make sure it's OK that way.
2 ) I would never re-use an oil pump that had any shards that went through it which would likely involve this engine.
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Whilst you have the engine out you may want to consider having the engine bay repainted, its something that you won’t regret and will never be cheaper than now without engine etc.
Oh yes, this is being done!
Two things:
1 ) any engine that spit/s out a rod bearing/s has a very good chance that the crank will be bent. I would make sure it's OK that way.
2 ) I would never re-use an oil pump that had any shards that went through it which would likely involve this engine.
Thanks for the advice. Great points. Trusting the Motoring Investments team on this one. Needless to say, they were surprised by the good condition of these pieces.
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A few more pics. New paint in the engine bay complete. Also a pic of the cylinder head after it was surfaced, the combustion chambers cleaned, and the valve seats resurfaced. :D
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Failure is usually caused by some type of lack of lubrication. Bearing wear is most often the cause. Which can cause it to overheat and spin, closing off the oil passage. Next extreme heat builds up from no oil circulation at the specific area. The metal rod ends and the bolts turn red hot and the connecting rod "stretch bolts" or the connecting rod itself fails. The fact that your camshaft had failed, could have been a sign that some type of lubrication problem was occurring. Dan is correct, with a crankshaft problem like this, the cranks usually becomes warped or bent from the heat and pounding.
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I had a 280SL spit out a timing chain while running on my hoist. I blipped the throttle a couple of times ( lightly ) and the engine stopped dead. I've never seen anything top that fast! The chain broke and at less than 2,000 RPM and it bent the crank about .012'' If the kinetic energy contained within a spinning crank was still enough to bend it when it stopped dead, what do think would happen to an engine that had a connecting rod fly apart?
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I was mistaken. The crank from the new short block will be used. Not the old crank.