Need opinions on possible engine damage.
 

All I wanted to do was stop an oil leak on my 1994, S350 TD (213,000 miles). I took the car to a non-dealer but experienced Mercedes mechanic. The "bad head gasket" was quickly identified as a cracked head (a well known design flaw in this engine). I had the mechanic check for bent rods and cylinder wear. Everything checked out fine. I said go ahead and replace the head.

Several weeks later I get the car back. It went 70 miles before "blowing up". The #1 intake valve dropped into the cylinder and broke up. Parts blew back into the intake manifold and went through the #5 cylinder. Obviously, major damage.

The mechanic rebuilds the engine on his dime (of course). Several weeks later I pick up the car. It goes 550 miles and blows up. This time it looks like the #3 cylinder had a valve being struck by the piston. The engine had a ticking sound like a bad lash adjuster, but it was not loud. Anyway, the disk/puck that the cam pushes against shattered, the cam broke, at least one cam journal mount broke, and that's what was apparent with just the valve cover off.

My question is, doesn't all this trauma to the engine have a high probability of causing unseen damage to things like the crankshaft, main bearings, rods, and anything else that's an internal part of the engine?

Also, the new head was setup by a shop that specializes in diesel engine work. On the first failure, they claimed the valve dropped because a "spin" weld on the valve stem just below the point where the valve keepers engage the stem, failed (act of God, not their fault). Anyone got an opinion on that?

The same shop assembled the second head. They haven't responded yet to the latest failure.

"Act of God", yeah right. Poor workmanship is what it sounds like to me. the "Act of God" claim could be feasable if the engine was damaged by a weather or geographical event. Valve stem failure would be caused by poor manufacturing, or an "Act of MAn"

Sounds like they did not check and double check everything.

I'm with RRGrassi on this one. They were supposed to identify the problem and fix it. blowing up 550 miles later is too close to be a coincidence in my book.

What an unfortunate sequence of events to happen. It also sounds like it is going to take quite an effort to get this all sorted out. Hope it all goes well.

At least there was no direct intent to mess things up. Other posters are right thought that an act of god does not quite cut it. Things can go wrong unintentionally. Thats why insurance exists.

Residual damage is also an interesting posssibility as you mentioned. There is not much happiness in an event like this. There now probably is enough money involved to need someones insurance company inputs unfortunatly. The safest action on their part would be to replace the long block with an exchange rebuilt. At todays costs they may be able and attempt to write the car off.

By the way this may be an opportunity to install the almost bulletproof 3 litre lower block in comparison to the 3.5 litre as well. In my opinion any opportunity to do that is very worthwile in my opinion. This whole situation just might have an upside. That does not in any way mitigate the stress of the event at this point much of course.

While part do fail it actually sounds like the Camshaft Timing was slightly of allowing some contact with the Valves.
There is also a possible that the first Time one of the Valve Keepers was not in good and came loose.

Also the Valves are only allowed to protrude a certain amout from the cylinder head.

Speaking in general with a Cylinder head is re-surfaced and the Valve Seats are reground. The Valve Stems will be taller (height) in relation to the inside top Deck of the head. The Hydraulic Valve Lifters can only compensate for a certain amount of Valve Stem Height.
To correct this on other Engines you grind the end of the Valve Stem to make it shorter.
Or in some American Engines they have shorter Pushrods you can buy.

Good point, the head should be measured to see if they took too large a cut if the head was resurfaced. I think very little is allowed as most members know.

There may have been direct involvement both times if it was over done. This is just a thought. Only measuring would verify it. It is the heads rebuilders responsibility to check a used head for deck clearance allowance.Before resurfacing. I suspect they just may have taken too much material off it themselves to true it up. Just a possibility. In no way a certainty.

As to your question: I would be concerned about the rods that were associated with any piston that was involved or hitting valves. I don't think I would worry about the bottom end unless debris somehow got into the oil system and circulated.
As to your issue: Sounds like the machine shop shaved the head too much, the head was installed with improper valve timing or the valve length (as mentioned prior) was improper for the setup. Inertia-welded valves have been in use for many years and while they do fail at the union of the two parts, it's almost always the result of an impact with the piston. Also, IIRC, the union is close to the head of the valve and not, as the shop stated, below the valve spring keeper grooves. Unless the MB valves are constructed totally differently than the domestic stuff I'm familiar with.

To the best of my knowledge, the cracked head "well known design flaw" was corrected long before the 1994 model year. I bring this up to question the experience of the mechanic, if it is not accurate (comments?).

The mechanic is supposed to check the quality of the machine shop's work. Perhaps they will buy & install a crate engine of your choosing.

Eitherway, this is thier responsibility to fix, and get fixed correctly.

My guess is shaved too much material off head, raised compression as well as chance of collision, with any slop in the chain / tensioner. Let me guess, no new chain went on?

Actually, I asked that a new timing chain be installed. The mechanic installed it at his own expense. A nice gesture.

Something is certainly amiss. Would seem to me that the mechanic? and the machine shop need to be buying and installing and warranting a new motor for you.

At this point Id opt for them buying the new motor and having someone who knows what they are doing install it.

IF, they agree to take financial responsibility, they will likely reference the value of the car, and consider it totaled / offer to buy you out as that is cheaper than a good reman engine. Good luck.

What a sad sequence of events. My sympathies. To my knowledge, God does not work on diesel engines. His time is mainly taken up with earthquakes, tornadoes, volcanoes, impregnating virgins and helping football teams.

The original cracked head concerns me. What was the history that caused it? Overheating? I would expect any smart insurance person to ask questions about this.

The first "new" head should have had all new valves etc, so if it did, the first replacement head should not have contributed to the 70 mile failure unless it had a fault, or was incorrectly installed. not an act of God.

The 'tick' sound when you got it back concerns me. Maybe a valve hitting a piston? Suggesting bad cam timing or a piston hitting the head? Wrong piston (not so likely).
I would be very concerned about reuse of that motor. It has had 2 unresolved major failures. Unless some one went right through the motor ( complete rebuild from sump to valve cover, fan to flywheel) I would not touch it. No one knows what other small near failures are now in the motor waiting to go bad.

It sounds very likely that the cam timing has been set wrong and with the stretching that occurs when the motor runs at speed there has been a serious collision internally. What were you doing when each failure occurred? 75 mph on the freeway?
A complete replacement motor is the only option, as to who pays ~ have fun !!!!

Well at last a little understanding by me of why some want to do god's work. I always wondered about their motovation before.

Have you been able to get the mechanic on the phone about this new failure?

These acts of god as the shop called it do happen, but that does not change the fact that the engine blew up again, and immediately after it was supposed to be rebuilt.

I had a situation once where I was replacing the glow plugs on a 2000 TDI for a customer, and the threads were destroyed on one cylinder since the glow plug had been cross threaded to begin with. I went in to carefully chase the threads of the hole, but I broke the tap off! :eek:
I pulled all the little pieces of the tap out that I could get, but I was not completely sure, so I had to pull the head and inspect the cylinder.

I come to find out that at some point in the cars life, the turbo had exploded and damaged two of the pistons and cylinders. It had been repaired by the dealer, who had picked all loose debris out of the cylinder, left the pistons in with dozens of little hot spots, charged the guy for a new head and new pistons, and sent him out the door.

When I found all this existing damage and showed the owner, he would not believe that it was not me who had caused this problem, even though the car had not been run after the tap broke off.

We ended up replacing his timing belt for him, and putting it all back together with new parts for free. We left the damaged pistons as well, we just redid all upper end stuff. The moral of the story is that **** happens, and these guys will have to be responsible for this new failure, BUT, it may not be their fault as they say. Does not change what it owed to you as the customer.

The fault could and probably lies with the machine shop, who may have used old stuff, or mis installed or machined this or that. The auto shop would receive a machined head and simply install it correctly with the assumption that the machine shop knew what it was doing. Many times, a mechanic who knows everything about how to put the engine together, may not be qualified to double check a machine shops work, and why should they double check?
Part of using a machine shop is farming out the labor to an expert. Its time involved as well. When you are sending something out to a shop, you are paying for the luxury of not having to put that time into that part of it. There is no point if you then have to go completely through it when it returns. They probably gave it a once over looking for bends, breaks, or damage.

A head is as complex as a transmission, and arrived as one unit. When a replacement tranny arrives, the auto shop does not take it apart to check tolerances, and does not really inspect it for anything other than large obvious problems. They probably got just a screwed as the vehicles owner.

My theory is that the machine shop used the wrong specs for this head a couple times.

The Next Chapter
 

I visited the shop yesterday to see what was going on and discuss some of the topics brought up in this thread.

The mechanic had the head off the engine and had disassembled it with a representative from the machine shop present. The mechanic showed me the head and we looked at the engine. There were no signs on the top of the pistons that would indicate they had been hitting the valves. The piston tops were a smooth almost semi-gloss black.

The #3 exhaust valve moved freely up & down. This is the valve that had the shattered lifter (the lower portion of which was jammed in the cylinder head). The #2 exhaust valve (I believe) was bent slightly (preventing it from moving easily) and its lifter had some light scoring (on the top). The cam broke in two places (both breaks near the damaged cylinders).

I don't believe all the valve components were replaced during either rebuild. I did request and received an new cam chain for the second build. Lifters not involved in the damage appear to be in good condition (no scoring on the sides or top).

So far, no word from the machine shop. The mechanic swears he checked and double checked everything (especially on the second build) and can find no errors in his work. He also said if he could see anything wrong with the work done by the machine shop, he'd point it out. I'm dubious concerning these last two observations. So far I'm being told the lifter failed, really bad luck.

I again mentioned the "tapping" noise the engine exhibited from the day I picked it up. But this is pretty much being ignored. Maybe someone out there can help concerning this noise. It sounded much like a loose tappet but seemed to come more from the lower portion of the engine than from the valve cover. It was barely audible from inside the car and was best heard by rolling down the window and driving past something that would reflect the sound back at the car (a building, jersey curb barrier, etc.). It got louder under a load but never sounded like a real problem until seconds before the failure. It was nearly inaudible at an idle.

Also, I'm assuming that if the valves came in contact with the pistons, there would be obvious marks on the pistons, right?

Thanks for every one's input on this. I'll keep updating this thread with my tale of woe. :(

Im not a fan of junk yard lawyers but this is a good case for one.

If they (the mechanic and the machine shop) dont respond by Tuesday
with a statement they are going to R&R motor with a NEW motor, Id
be having the JY legal beagle send them a demand letter. Any court
action would of course INCLUDE your JY lawyer costs.

They screwed up. OUR motors are not cheap. THEY need to fix it and
do so now and properly.

The problem here with acertaining the actual cause. It might be impossible. All that may be visable now is the residual damage.

It may be almost impossible to tell what went out first. I would think without actually knowing that a lifter shattering is not only very unusual but I am trying to remember if I ever even heard of that type of failure before. . Certainly without something else failing first if it were to occur. It takes substantial force.

If the cam is not broken ahead of the number two valve how did the number two valve get bent? So I assume the cam is either broke ahead of the second valve as well or the engine has jumped chain timing during the event.

This event could have occured by the towers that support the cam not being in line accuratly bearing wise. Or more likely there is a specific sequence to removal and installation of the camshaft towers pecular to the 603s that may not have been followed correctly..

After putting the towers back on the engine I would want to hand spin the cam to at least have an indication there was no binding prior to installing the rockers. It also may have been damaged at the time the towers were taken off the head.. I doubt if anyone checked the camshaft at any time for any runout. I guess what I am trying to state that if you do not have the service information or knowledge on working on the 603s you could damage the camshaft.

I would not discuss this with the mechanic or the head rebuilder. Your lawyer could prevail in discovery by asking the mechanic or machine shop the sequence of or methology used in removal of the cam and towers.

If whoever removed the cam etc does not know the required sequences you have them.They are probably very confused themselves about what transpired. Not an act of god without following the correct methology. Best of luck.

"Sorry for your loss"
 

cdavidson,

"Bob" And "Barry" both have your answer(S).

Do not get involved in the "Finger Pointing"...
That MAY occur between the Mechanic and the Machine Shop.

(or, they MAY elect to BLOW you OFF, COMPLETELY...Which is what's Happening with "Too Bad ,So Sad about your Lifter")

These guys KNOW they've "Bought the Farm" [Your New Engine] and are
trying to "See" if you're gonna walk away with a "Fairy Tale" in your teeth.

Demand Letter from Law Office ('Cost you less than $100.00) to BOTH!