94 E420 timing chain guide broke into engine. Is that a problem?
 

Here is the right head with the guide intact:
http://www.fototime.com/BF8708B53200C71/standard.jpg

On the left head the top part of the guide is missing and all I found when taking the cover off are pieces I have placed on the power steering reservoir:
http://www.fototime.com/F0CD4EDA927B9F2/standard.jpg

It could have been like this for many thousands of miles without a problem so should I worry about it now? I assume any big chunks would just drop to the bottom of the pan and any small bits that would have gotten past the oil pump screen would have been pulverized by the pump and caught by the filter. The car runs fine with strong oil pressure. What parts do I have to replace and how do I tell if the chain is worn? It has over 160K miles.

atikovi, one of the broken pieces could cause the timing chain to jump one tooth, or more, and trash the engine. If it were me I would drop the oil pan and remove all the broken pieces and install new timing chain guides on both sides. It's not worth the risk leaving broken pieces inside the engine.

You ask about chain stretch- but I believe you are looking at the evidence of chain stretch!
Yes, it can be checked. Rotate engine around on TDC(turning it clockwise) and then see where the RHS cam is with respect to the timing mark. I bet it's way out- 10-20 degrees.
Yes, you'd be best to remove all the pieces. It could be in the cover still and lodge with sprocket-cause chain breakage- and then your in for an added valve job.
Looks like your in for a big job- read up on replacing the chain. Big job. I'd use on a wjis chain and factory guides. Replace as main guides as you can get at. FYI I've never done one on a M119 engine-yet.

M

I would say...not a big deal...I would look into this thing however, like you say, you don't know long it's been like this and it hasn't caused any issues and, frankly (and don't take this to heart young people) it is an extremley bullcrap issue anyway...if it fell of into you timing chain assembly you wouldn't know about it? A dual roller-chain timing assembly held together with a plastic cover? No...absolutely not....it's a cover that probably got tossed by a mechanic at some prior servicing.....he decided to toss it rather than charge (and piss off) you for it to be replaced ...forget about this....

I'll replace both since the one still there is cracked and can go anytime. Since it's made of brittle plastic I'm not too worried about it causing damage from lodging in the sprocket, the chain will just grind it up.

I changed mine a while back. Maybe this post will be of help to you.

http://www.peachparts.com/shopforum/tech-help/212671-400e-upper-chain-guides.html?highlight=400e+upper+chain

Regarding the timing chain stretch, I was never able to get a definitive answer on how to check it. The job in the shop manual (attached) has a procedure for "[c]hecking, adjusting basic setting of camshafts," and it has you pin all 4 camshaft sprockets with the 6.5 mm pins at the camshaft bearing caps, after turning the engine so the vibration damper is at 45 degrees BTDC. It says that "it must be possible to pin the camshafts with the pins," but it does not say what it means if you cannot do this. Then it goes on to tell you to "fit on" the timing chain (maybe I missed it, but I can't find where it has you take it off).

I was wondering if you could check for stretch by turning the engine until the pins did align, then check the damper to see how far off from 45 degrees it is.

Any thoughts on this?

Thanks for the link. As for checking chain stretch, that's way too complicated to go through. I just want check it how you did with a finger pull up on the chain between the cam sprockets. Mine seems much tighter than your pictures so it must be OK.

I'm not sure that what I did is a true reflection of the chain stretch. My chain tensioner could have been weaker than yours at the time. My feeling was that, even if the chain was stretched, the new upper guides would have at least reduced the likelihood that it would jump a sprocket tooth and take out some valves.

Snaking a new chain in is a job that I know is beyond my mechanical abilities. I considered just changing the tensioner, which only involves having to pin the passenger side cams with the 6.5 mm pins (this prevents the chain from jumping the cam sprockets when the tensioner is removed). In any case, it's moot now, because that car is in the junkyard.