k649

these should be straight up and down as my cam was a bit tilted.

still trying to save this car. removed some wire harnesses and it looks like to get the valve cover i'll need to remove the oil filter housing, PS reservoir, oil separator, fuel rails ...

and to remove the head, the two bolts on the exhaust pipe are almost impossible to reach.

eric_in_sd

Tell me about it. I managed to pull the cat on that side (sadly, it was unnecessary surgery, but oh well) and reattaching it was horrible. Had to have a helper up top and everything.

I think you might pull the exhaust manifold to take the head off. Not sure.

I really doubt it is worth the effort. Maybe I'd pull the valve cover and try to figure out what happened, but I really don't think it is worth the valve repair. Think about it: Do you want to be driving your family around on road trips in a vehicle with a band-aided motor?

Another approach: Since you seem mechanically inclined, I really recommend getting a better borescope. Here is a picture of my combustion chamber with my Teslong.


I was using a simple one attached to my phone, but the resolution and image quality on the Teslong was what saved me: I was able to identify carbon buildup on the undersides of the valves.

Just my recommendation.

Jeedie

Check , this guy installs the head with an exhaust manifold attached. Probably due to those exact same two bolts.

k649

Got the valve cover removed. Mercedes likes to make things difficult so i had to cheat a bit. Should have removed the fuel rails, PS reservoir, heat shield.

See the pic below. For whatever reason the rocker arm (?) is not on the valve spring! Anybody has any idea why this happened? And the solution is just moving it back to its position? sounds too good to be true ..

Jeedie

Good job you got the cover off!

It's a bit hard to see, but to me it seems the valve stem top has some dents and somehow seems to point in the wrong direction, especially compared to the valve next to it.

The fact that the rocker arm has popped of is not that surprising. From the indent on your piston, there was some unplanned contact between valve and piston, which must have led to unexpected forces on the rocker. Maybe it found a way out by moving sideways.

I expect the moved rocker to be an effect of the problem, not the cause.

BlackML550

That's a "head off" repair if you want confidence in the fix. The lifter and/or rocker arm has failed. You'll want to be sure of no piston to valve connection and then the fix for the lifter and rocker arm, as well as any underlying damage to the valves, valve spring, the head and the cam. Working out why it happened is the most important part. I'd say you're in luck with this.

Have the heads been reconditioned at all? They look very clean for a motor with 220k miles.

eric_in_sd

It looks like the valve keepers failed and came off. The top of the valve stem was no longer tied to the spring. This allowed the valve to drop down and the rocker arm to shift sideways.

If the rocker arm had merely shifted sideways, the valve would have been stuck closed.

k649

@Jeedie so the theory is that something got the valve stuck, then the piston hit it and knock the rocker arm off?

@eric_in_sd i'm not sure about the keepers. if they did come off, it's gonna be a another big problem. i'll take more closeup pics but it's also possible that the rocker arm is partially on the valve spring, holding it 1/4" open all the time.

@BlackML550 not sure why i'm "in luck" as i tried not to pull the head -- very difficult exhaust pipe bolts, cam wheel pins, TDC+40 degree, tensioner, oil filter housing ... whole bunch of things to remove and i don't have a proper youtube video or WIS instructions. I got this car at 105k miles. guess no head work was done before.

at this stage what else can I do? pushing the valve down with a socket/tool (with the piston all the way down), and spray carb cleaner or blow with compressed air?

or forget it. just take the head off no matter how difficult it looks like? i'll replace this car in 2 years so trying to minimize the work ...

BlackML550

It's obvious you're trying to salvage what you have - or you wouldn't have gone to all the trouble with this thread - and it looks like it might be salvagable. That's why you might be in luck. You can spew all the technical specs and dramas you like at me, it's still easier than finding a decent replacement engine and having all that done, not to mention the cost, and introducing more risk to your equation. This repair is beyond you. Take it to a decent shop and let them do it. Best of luck with whatever you do now you've become an expert.

eric_in_sd

Good job getting off the valve cover and finding out a little more about what is going on.

It is difficult to know from description and from photos just what happened.

Poke at the top of that valve stem. You may be able to push it down slightly. The top should be anchored to the cap on the top of the valve spring.

Try looking around at the well around the spring to see if you can find the keepers. They tend to go flying off.

It is also possible the valve stem snapped; that would explain why the visible top of the stem looks rough.

It is unlikely you will be able to get an adequate compression seal between that valve and the cylinder head. The stem is probably bent, and the edge of the valve that hammered the indentation into the top of the piston is probably also bent. The valve guides are soft metal and are very likely bent into an oval clearance hole.

Try poking around the top of the valve spring. See if the spring is sitting loose, and whether the top of the valve stem is broken or is loose. Let us know what you find.

Jeedie

Well, it's pretty hard to tell from these picture what the course of events has been. Do keep in mind that the rocker cannot move away on its own under normal circumstances, it's pressed into position by the valve spring. So it would seem logical to me that the valve got stuck (yet to find out why), causing relief of the pressure on the rocker, hence allowing the rocker to start moving. Again, this is just speculation, not a fact.

The damage itself seems limited, that is the good news. Now of course, paying a workshop to remove the head, fix everything etc. will still be expensive, as it's not a small job. So think of it this way, the parts bill will probably be pretty limited, it's the work itself that adds up. Up to you to decide how to approach this:
- Perform the work yourself, hence reducing the bill in a big way.
- Bring the car to a garage and have them perform the work.
- Ditch the car.

>> very difficult exhaust pipe bolts, cam wheel pins, TDC+40 degree, tensioner, oil filter housing ...

This forum might be of help here. I can access and forward relevant WIS documents. The exhaust manifold can be left attached to the head when removing the head. The 40° TDC should be easy as long as you have the right markings on the crank pulley. It's all doable, if you have the time, place and tools. You could consider lifting the head and bringing this to a specialised engine workshop, they should be able to assess the damage and cause, and repair where necessary, giving you the comfort that the issue will not return after all the hard work.

eric_in_sd

@Jeedie analyzes pretty well, all though I think he is being optimistic about the health of the rest of the motor.

To help it make sense, I will speculate on the root cause and order of events:
1) Spark plug insulator breaks apart
2) Chunk of insulator jams intake valve open
3) Rocker arm is no longer held in place by spring tension, and wanders off
4) Piston strikes descended valve
5) Valve bends, jamming it in place
6) Piston repeatedly strikes descended valve

The likelihood of the keepers coming apart on their own after 220K miles is almost zero; same holds for the valve stem breaking. However, these are only somewhat less likely than a spark plug insulator spontaneously breaking. Did your teenage son go racing your GL, doing continuous revving to redline at full throttle? This whole episode sounds like an engine placed under severe stress.

In any event, the chance of some miracle, such as the rocker arm just needing to be pushed back into position, is about zero. If the valve were straight and still happy with the valve spring, the valve would not be descended. You have to pull the head; plus there is a very good chance the cylinder wall is scored, meaning you will probably not escape with simple valve repair. No one in their right mind would take this on for an engine with 220K miles on it, which is why your shop told you to go away.

Get a replacement motor or sell the whole thing for parts.

k649

Appreciate your input @BlackML550 @Jeedie @eric_in_sd . I decided to hire a guy to pull the head for me as most shops won't even try it and the others quoted $5000+. and man, this job is brutal. especially the last exhaust bolt was stuck in the bolt. it took him like 2 extra hours to pull the cat and everything off and finally twist and broke the bolt.

Here are the pics. The valve is bent, both keepers are gone but i only found one. piston indented a bit ... And more questions are raised:

1. One thing worries me is he didn't follow the book (like the TDC+40 degrees, or pin the exhaust wheel gears). I heard many mechanics just go by the feel instead of using torque wrenches. But this could be a big timing problem while assembling, right?

2. closer look at the spark plugs. Two of them were bent (one of them lost tip ceramic part). What happened to them??? the spark plugs are hidden at the top of the dome shaped head.

3. He said it could be the timing chain. If it's stretched and the cam gears skipped, and the piston hit the valve (and spark plugs).

4. Today is sunday and tomorrow is the presidents day. I'm going to a head shop as soon as they open. But in your eyes is this engine salvageable at all? to get a used engine installed is less than $4000.

Jeedie

We would need better pictures of the offending cylinder walls. The head will be salvageable, replacing the valve, valve guide, maybe reseating of the valve. The missing retainer keeper should be found by the head shop if they do a proper job. Make sure to warn them you could not locate one and inform them of the failure of the engine, maybe they can figure out the issue. Oil starvation on the valve stem might lead to a stuck valve, it's possible that this has occurred.

Regarding the engine, I would not worry too much about the piston indent. Most of the indent is away from the fragile ring land.

If the cylinder wall checks out okay, ask the head shop for a quote and decide if it's worth the repair. If the cylinder wall has scoring, you'd better forget about any repairs.

k649

here are more pics of the cylinder wall. there are some scratches but they appear to be above the piston.

just found out the guy broken one of the chain guides too!

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eric_in_sd

Can't speak for others, but I certainly appreciate your taking the time to post these pictures. They will help others understand what is going on with their motors.

Pretty much what @Jeedie said.

I am confused by the talk about keepers. What's being held in the mechanics hand in the middle couple of pictures is the hat (washer?) that sits on top of the spring. The keepers are halves of a section of a cone.

The damage to those spring hats looks like it was done by the rocker arm going off center.

The damage to the cylinder wall is uncertain; it appears the stuck-open valve banged sideways into the cylinder wall four times. This is probably not an issue, but I can't tell for sure; it is within the range of the piston rings' travel - look at the clean portion of the cylinder wall versus the combustion portion - so you will likely get blow-by because that is at the portion of the stroke when the combusting gases are at their highest pressure. Honestly, based on that alone I would say the head is not worth rebuilding. I don't think any sensible mechanic would rebuild a head when the cylinder wall has dents in it. Combustion gases will blow by those dents and wreak havoc on the rings.

I really have no idea how the spark plug ended up so boogered. Something hit the ground electrode pretty hard. The presence of these unknowns makes me all the more skeptical about the feasibility of a repair.

Swapping in a motor should cost you much less than $4k. Last I checked, those motors were about a thousand bucks on Ebay - and you are literally just looking for something to last you 25k miles or so. Swapping the motor is not child's play, but really it's just disconnecting from the transmission and unhooking the electrical, exhaust, fuel, and coolant lines.

Max Blast

I don’t know why you’re so hard over on trying to salvage this catastrophically failed motor.

I do enjoy the pistectomy carnage you’re posting, but know that it would be much easier to just slot in a known good used motor. Drop front subframe, remove old motor, offer up new.

also, your notes on your “mechanic”’s work habits make me sincerely doubt this motor will ever go back together proper like again.

k649

@eric_in_sd yes the keepers are the cone shaped halves. they were not on the spring. One was found in the head. The other is missing. and you are right, the dents are within the piston's travel. but they are probably not as bad as they look coz my fingers cannot really feel them there.

I looked at eBay too and most are $2k and up for M273 5.5L 4matic. Labor would cost $1.5k - $2k (my understanding is a 2-post lift is necessary). So the total cost would be close to $4k. Also, are those ebay sellers trustworthy? like any ways to verify the mileage numbers on those engines?

@Jeedie oil starvation caused by oil overfill? let me think .. the time sequence is like: misfire --> spark plugs change (2 bent with 1 broken) --> oil change with a little overfill --> good for 2 days then horrible misfires. So i guess at least the spark plugs bent and missing ceramic problems are not related to the oil.

@Max Blast the top reason is obviously money. Also i want to find out why this happened -- timing chain? oil starvation? defective plug? carbon buildup? And I learned a lot during the process.

cylinder wall damage, timing chain stretch, incorrect head removal --- any of these is fatal to the idea of restoring this engine.

eric_in_sd

Ebay is cited only as a guide. You are in southern California, home to thousands of these e55 motors. You'd start by finding a reputable shop to do the swap. Most of these shops are quite able to find used motors, and are inclined to stick with trustworthy sellers. Used motors generally come with a warranty against prompt failure, and the shop will back up that warranty.

I wonder where the other keeper went. Down the oil galleys?

It is fun and enlightening to do the diagnosis, but it does get expensive after a while.

For anyone else reading: Note the grit accumulated around the top of the block. This illustrates why you need to work with a good shop: Cleanliness is paramount when it comes to engine innards. It is anyone's guess how much of that grit has fallen in the cylinders and intakes.

01blackhawk

Looking at those pictures, I`m just curious, seems like you have this vehicle for a while, have you happened to use any additives to prevent the carbon buildup? Looks pretty cooked to me compared to some other pictures I`ve seen here and there.. Wondering if this is normal buildup?