Firstly I would not be trying to start it. You risk doing more damage than has been done. These are an interferance motor - if you continune to crank it - the valves (if stuck open) will hit the pistons and you'll do more damage as well as potentially to the valves, lifters and cams. You should really follow the good advice people have given you to date.

Can you confirm that the piston in No. 5 moved up and down as it should? Get some pictures of the valves. That will be most likley your problem.

The ceramic tip from the sparkplug will most likley be long gone, so don't expect to see it. The top of your piston looks OK based on these photos. The wrinkles on the top are oil and unburnt fuel.

Get photos of your valves, as well as cylinder walls by hand turning the crank. Take photos of valves and walls at various positions of the crankshaft rotation to look for i) damage to cylnder walls and ii) if the valves are actually opening and closing. Id also be taking off your valve cover and looking from the top to see if everything is at it should be. Instinct tells me thats where your problem may be.

 

thanks and yes i can see the piston is moving up and down.

yes, i'll not start the engine.

the wrinkles could be the result of piston hitting valve?? they are not oil as other pistons look flat. just this one got big wrinkles.

i'll get more pics/video of the valves and stuff tomorrow.

 

You have a piston that goes up and down. The only other obvious reason that you could have zero compression is a valve stuck open. That will damage the face of the piston, although it doesn't look as bad as many in this situation. Much of what you can see maybe just oil and unburnt fuel, plus some damage caused by the spark plug breakage and possibly the valves.

Get the photos of the valves at various points as you slowly turn the crank by hand (doesn't need more than 1/2 to 3/4 of a revolution), and then we will know.

 

Nothing on that piston head looks out of sort

 

I agree with Black.

There's no way that "wrinkling" is from the valves. Something was boucning around in there - that broken plug could do that till it was finally broken up/expelled. I'm not too worried about the piston - the question remains regarding the condition of the valve/seat.

It definitely looks like unburnt gas mixing with oil - which would make sense sense since that cylinder wasn't firing.

As mentioned above... try to get a few shots of the cylinder walls.

 

I don't understand this "wrinkling". Are you talking about the indents? Those are to provide a safety margin for the valves.

Are you talking about the rough, dark surface? That's carbon, not a big deal.

Here is one of my pistons from when I was cleaning out the carbon.

 

You are looking for one valve sticking down more than the others.

I hope your borescope has a genuine side view, because that makes looking at the valves much easier.

It is not unusual for the combustion chamber to be wet when you are messing around like this.

Scoring on the cylinder walls is a mixed bag. Sometimes it is due to carbon and oil resting at the low spot on the top ring, so it looks like scoring but it's not.

This might be a photo artifact, or it might be a dent in the top of the piston from the valve


That would be your front-most intake valve, if on cylinder 5 it is the very front-most intake valve.

 

Looking at the placement of this indentation, I hate to break it to you, but it sure looks like you dropped the front intake valve, possibly due to a broken valve spring, or maybe a failed keeper, and at this point ... I dunno, maybe have some fun seeing how long the motor runs with the oil and coolant drained out?

Conceivably the motor could continue its life with a dented piston top, replacing the valve or valves. I would not invest that in a 220K mile motor, though. You are in an excellent area (Orange County, right?) to get a used motor. Lots of that vintage Benzes running around there.

Whatever wrecking yard sells you the used motor might give you a few bucks on your "core".

It's a real shame, my friend. Sorry.

 

By the way, the indentations in my piston tops look different probably because it's a e47. Different pistons, cylinder heads.

 

thank you all, my friends! very helpful info here

if the piston is good that's good news coz it seems that it's possible to do an in-frame job of removing the cylinder head, as i don't have a 2 post lift. will see if it's something that I can tackle in my garage. engine swap is expensive in OC (and elsewhere i believe) ...

the borescope i got has a mirror attachment at the top. somehow the images are not very clear. i'll try again tomorrow, turning the crankshaft while watching those valves as you suggested. also will try to inspect the walls. if no luck, i'll get a better borescope.

just curious if it turned out to be a spark plug problem in the end, does FCPEuro or Bosch need to take some responsibilities?

looking at the piston again, is that a gap circled in red leaking oil?? just wanna be sure ...

 

Things break on cars. And good luck with claiming on an engine with 220k. The circle you have noted is simply the flim of oil from the cylinder walls seeping down to its lowest point when you stop the engine. Some of it might have come via the valve train if you have damage up there. I'd suggest its the least of your concerns right now.

 

sorry forgot to mention these spark plugs are 2yr 3mo old with 50k miles, not 223k miles.

good to know the piston is ok. it's a little easier to just remove the head.

 

FCP, I'm sure, would send you a new spark plug. But that would be the limit of their (or any retailer) responsibility. I don't see how Bosch would have any liability here, either. The ONLY way you would get some kind of liability coverage (and I doubt it would even happen then) is if you paid your Mercedes shop to do the work. They "might" cover subsequent damage from a part they installed with their service warranty... "might" being the key word.

 

ok i watched the 4 valves while hand turning the crankshaft. One of them is not moving at all. it's stays open 1/4 - 1/2 inch. It appears to be on the intake side (see the mirror in the pic below). The other three go up and down.

unable to get a good view of the wall yet.

My question is if the valve spring is broken, it should be able to open all the way but just unable to close, right? or the camshaft is broken? or something else?

 

It's now time to take the valve cover off. You might well have an engine thats salvageable.

It could be a broken valve spring, a bent valve, a damaged/stuck lifter, broken retainer, or the valve has seized inside the valve guide. All can lead to the valve remaining open. Assuming only 1 valve is malfunctioning, it might be a simpler fix. Pistons hitting valves usually result in all 4 (or 2 on 1 side) being damaged which indicates a valve train problem as the cause. But until the valve cover comes off at a minimum, you won't know.

There's a chance to get out of jail here, depending upon what the cause is. But the head(s) needs to come off for any fix.

Time to find a good indy mechanic. Your safest option might well be a 2nd hand motor given miles and all the other things you might want/need to do.

Looking forward to 'Season 2' of this diagnosis.

 

Yeah this is confirming what I said earlier. A valve spring, or the keeper (which is what ties the spring to the valve), has failed and the valve is flopping around in there. The cam pushes it down, and then it stays down until the piston comes up and bangs it back up. Take another close look at the new and improved valve clearance cutout on the top of the piston.

That valve's guides have been re-shaped to accommodate the violently forced-back valve stem. This might be the cause of the apparent oil in the cylinder; oil is leaking down the valve guide.

Conceivably you could continue running with a new and improved valve clearance divot in the piston top. But in any event you will be talking valve surgery for at least your bank 2 cylinder head. I don't know of anyone in their right mind who would do this for a 220K mile engine.

If you really want to do a post mortem, take off the valve cover and look for a broken spring. However, I think it unlikely that a valve spring would work normally for 220K miles and then break; that seems more like an early life failure. Ditto for the keepers failing. The hydraulic lifter failing would only result in the cam-valve clearance going too high and the valve failing in the closed position.

The only reason I'd do this post mortem is in an attempt to rule out it being the insulator chunk. The only reason I'd doubt the insulator chunk being the root cause is because, due to air flow, such a chunk would typically only get stuck in an exhaust, not intake, valve. But absent the spring or keepers failing, the valve being jammed open for the piston to collide is the only root cause I can think of.

I wouldn't spend any time worrying about blaming someone, such as Bosch. Best case, you have the fair market value of a 220k mile engine, which ain't much. It couldn't hurt to bug Bosch about it, just to see what they do, but don't get your knickers in a twist over it.

Again, my heart goes out to you, but in situations like this we just have to take the hit and move on. Get a motor in it or sell it as a non running vehicle.

 

thank you @BlackML550 and @eric_in_sd and everybody else for the detailed and helpful info.

yes the next step is to remove the valve cover and find out why the valve did not get pushed open by the cam all the way, and get ready to remove the head for any fix. the job is kinda intimidating. BTW i cannot find any good videos for the driver side valve cover/head job. looks like i'll need to remove oil cooler, PS reservoir and a bunch of other things. What's the best source of WIS then?

my original plan was to keep this car for 2 more years and get a cyber truck (1.2 millionth in the tesla queue). now need to get mentally prepared for the worst. what's the best source of used engines? ebay got some inexpensive M273's but is it trustworthy? what's the best way to ditch a car? selling it non-operable will take a long time? junkyards pay close to nothing i presume?

nah wouldn't waste any time with bosch or fcp coz nobody would admit fault even if it's a defective product. hard to prove anything.

never imagined a spark plug could cause catastrophic damages. i told myself this is my last gasoline car a couple of years ago. maybe i'll just stick to diesel and EV in the future.

 

It's not a small job and requires plenty of thought about putting it back together afterwards no matter what the outcome. No one wants a truck with a head that needs reattaching so I'd be suggesting a shop that can do it quickly and easily.

If you want to do it, noting that you might need some machining of the head (which means you really need to do both heads), post your VIN (best on your profile) and I'll download the WIS data for you. That, when you read it might scare you off!

 

i know it's a big job but a guy on youtube put the head and everything back in 1+ hours. I figured gimme a week it's doable?

so i'll have to machine both heads? that youtube guy seemed only machined the passenger side one (valve seats).

and even if i mess up, it's a dead engine anyways right? the core only is worth "a few bucks" as mentioned by @eric_in_sd not much to lose here correct?

my indy shop doesn't wanna do it -- saying what if they find more problems after opening this old engine up? or if possible, do you know where to hire a professional mechanic to help me in my garage during weekends if this is getting beyond my abilities?

i graduated from youtube univ so WIS is quite scary to me. my VIN is in my profile now. Appreciate your help!

 

I'd say that's the best outcome possible for a valve issue. Piston has an indent, but not too bad. Valve is stuck, so hopefully it did not slam the valve seat. So it might be that you have very little damage all in all.

With the engine @220k, I would not worry about the piston indent or event any bending of the rod below. I've just read about a guy driving with a severely bent rod due to hydrolock for over a decade, he never noticed. That little indent on the piston will have a negligible impact on the compression ratio. If the valve is stuck open, the valve seat will be okay as well.

Steps I would take from here:
- Remove the valve cover.
- Inspect cams etc for any damage that might throw off the plan. As you have normal compression on the other cylinders on that bank, I expect the camshaft to be okay.
- Remove the inlet camshaft.
- Remove the head, if possible with the exhaust camshaft in place.
- Remove the offending valve. Check if it's bend (it probably is).
- If the valve stem is bend, it will have damaged the valve guide. So, remove and replace valve guide.
- Check valve spring, lifter and valve retaining clip. See if you can find the cause of the issue. Replace parts that need replacement.
- Check the head (and block) for flatness using a straight edge and feeler gauges. If it's all within spec, do not skim the head.
- Clean all surfaces.
- Carefully inspect the valve seat for any damage.
- Install new valve etc.
- Check for leaks around the inlet valve (e.g. )
- If all checks out okay, install everything on the engine, use a new head gasket etc.

 

It is certainly doable. I would start with taking off the valve cover and attempting to determine why the valve dropped. You will want to do that to satisfy your own curiousity, and it is not a difficult job.

@Jeedie posted a sensible and legitimate summary writeup; missing, of course, is all the junk on the top that has to be removed, such as the intake manifold, power steering pump and reservoir, fuel injectors and rail, radiator, and and and.

Most used engines are provided with a warranty.

Don't try to figure out now what course of action you will take, because it depends on how you feel about the vehicle. Is the rest of it in good shape? I keep my GL because I want to have available a towing and off road capable truck that I can sleep in the back of. If I were to get diesel, which is compelling, I would get an earlier one that does not use DEF. No way would I get an electric vehicle; the battery cost makes them very expensive to operate long term, plus they are dependent on the electric grid, which in OC I would be even more nervous about.

If the rest of it - the body - is in good shape, it can be kept alive indefinitely.

Try to figure out why the valve dropped, and go from there.

 

My guess is that the valve is stuck in its bore because it is bent. It is bent because it hit the piston. Open up the valve cover to see if there’s other damage, such as a collapsed lifter, broken spring or wiped cam lobe.

the piston may have cracks in it you can’t seee with the camera so roll the dice on that. You’d have to do a leak down check once the valve seats itself again, I doubt you will be able to unless you repair it. It’s bent and will not travel freely in the bore. Have you looked at at cylinder wall at BDC for scoring?

in my opinion none of this is economical to fix with mb parts, I’d just drop in a lower mileage motor. It’s not like this is a frequent occurrence either.

had this happen in my GM 6.2 v-8. That’s a new motor under warranty due to the severe valve train damage and cracked piston, cylinder wall and bent pushrods etc…

 

@Jeedie appreciate the crystal clear instructions. i'll remove the valve cover and take a look inside.

@eric_in_sd it's a 16 year old truck with some issues, but it's our only tow vehicle taking my family to 40+ states. Our Sprinter 2500 is only capable of towing 5000#, not 7500#. The plan was to keep it (and our travel trailer) for 2 more years so i just get it running again. Cybertruck may not work for me with the raised price and poor range numbers. I may just get another X164 or X166. What do you guys think of bluetec? yes DEF is a pain but dealing with vintage cars is beyond my skillsets.

@Max Blast no walls yet. the amazon cam doesn't have side views. i'll need to remove the valve cover no matter what.

 

tried to walls again and these are the best i got. are these scratches/dents something i need to worry about? some of them look nasty ..

 

It's hard to see much of anything but that straight line catching the light could be a gouge in the wall. They are typically straight up and down, though.
If you're looking for another x164 why not just use this one for parts?