You've touched on almost everything that I can think of as over heating goes. And a note, if I read you correctly, but pushing up on 100 degrees with a/c on is not overheating. I live in southern Nevada and 100 degrees is fairly normal and my current 14 head is as old as everyone else's.
I would consider looking at the water pump impeller condition. It is possible that an old pump could be deteriorated enough to not be pumping well but not make noise. Can't say I've seen that on an MB, but I've seen it on other stuff. Though that wouldn't contribute to smoking exhaust.
And, btw, you can drive one of these with a cracked head for a long time. I did for about 2 or 3 years daily. The crack must not have been very big on mine, but it kept that top rad hose hard most nights. However, I didn't have the money for a fix at the time and just thought, well, drive on, drive on. There was a little oil in the coolant, but she actually ran well. And looking back on it, I should have taken the head off and welded it. But I sold the old girl.
I believe these engines suffer a lot when left to sit - diesels more than gassers. If yours wasn't driven much and you've got combustion on all six and decent spray patterns from the injectors, then you probably need to drive her and drive her hard for a while. I would also consider liquid moly oil - the good german stuff. I've been very happy with that change over on my 603.

__________________
DS
2010 CL550 - Heaven help me but it's beautiful
87 300D a labor of love
11 GLK 350 So far, so good
08 E350 4matic, Love it.
99 E320 too rusted, sold
87 260E Donated to Newgate School
www.Newgateschool.org - check it out.
12 Ford Escape, sold, forgotten
87 300D, sold, what a mistake
06 Passat 2.0T, PITA, sold

Las Vegas NV

Replaced both fuel filters. No change.

Will take a look at timing over the next few days.

Finally had a chance to check out the timing today. Looks bad.

Guess I need to look up changing the timing belt. At what point do I need to worry about damage to the valves/pistons for interference?

Attached Thumbnails

   

chain.

are you before top dead center?

how did you rotate the engine? did you turn your engine clockwise at the crank?

I've had a couple of MB diesels and I've only once seen the prefilter black like that... my 602 sat for several years and was driven infrequently by the PO. When I bought it, rough idle, sounded like it was nailing, smoky. For giggles I ran two tanks of b99 biodiesel through it. First tank turned the prefilter black. Changed the filters and ran another full tank of b99. Changed the filters again. All of the noise / ticking that I thought was nailing disappeared. It stopped smoking too. Clean prefilter for the last 15k miles.

Not trying to make an apples/oranges comparison to your situation but I feel like you've got some mung in your fuel system.

EDIT: Strike all that... just saw your timing chain pics...

__________________
1991 300D 2.5 "Rocinante"
2002 Golf TDI "Teen Spirit"
--------------------
1984 300D
1966 Mustang I6 3sp
1985 Mazda RX-7 GSLSE
1982 Toyota Supra
1977 Datsun 280z
1971 Datsun 240z

Redo your timing chain check. Your cam mark is not yet to the alignment mark on the cam bearing cap and your crank damper shows you're 17˚ BEFORE TDC which is not possible with chain stretch.

Make sure you're turning the CRANKSHAFT bolt, not the camshaft bolt.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Turn engine only clockwise. Turning with the alternator nut. Although not recommended. Is turning the crank pulley. Turning with the cam sprocket as mentioned would be counterproductive. It could gather the chain slop in the wrong place. Producing a bad reading.


Do not assume the chain is badly stretched yet either. As for valve train damage I suspect not at this time. Recheck timing again as suggested. Post what you are getting.

You’re allowed 3.5 degrees of timing chain stretch before recommended replacement. If your car was maintained and oil changes it should last an easy 300k. It’s a double row heavy duty timing chain. Not built like a Corolla. If your timing chain is truly that stretched you’ll be hearing rattling right on startup that gets louder with higher RPMs. When the chain is stretched too, no matter how good you are at adjusting the IP timing, you’ll never get it right.

Your car is fine I wager. Take it out and run it for what it’s got and put it to kick down.

__________________
Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

I had read in a post to get the cam flange mark to the passenger side of the cam tower mark. While its a more precise location, I was curious how close I could get it to right on.
I took this pic yesterday with the smallest movement of the CRANKshaft bolt; As a few queried, I only went clockwise.

As far as stretch goes...how is that tested. I tried lifting the chain (I said belt before, my bad) vertically at the top of the cam gear, with my fingers. I got nothing. Seems like if there was any slack it would all be on the tensioner side.

How it could end up at before TDC is mystery.

Attached Thumbnails

   

Either I'm missing something or there's some misinterpretation. At ~16 deg before TDC how could the car be fine?

that's good you're supposed to turn it by the crank bolt

your chain is in good shape. Don't need to change it.

it's not a mystery. The chain was installed incorrectly. All you have to do is remove the tensioner and move the chain one tooth on the sprocket and you will be good to go.

1 tooth = 19 degrees on the crank

Well thats a mystery. I'm pretty sure this is the original chain. All this happened while driving...how'd the cam get ahead of the crank by one tooth.

Well that does sound simple. How did you arrive at one tooth?

Just becuse it's original doesn't mean it hasn't been removed at some point


360 degrees / 19 teeth = 18.9 degrees per tooth

1 tooth = 19 degrees on the crank

wrong cam timing contributes to your problem but I don't think it's going to solve it


the best way to check for a cracked head or a head gasket leak is to do a leak-down test

Correct the timing. New noise gone? It was an issue. Noise in conjunction with your problem is somehow a factor. Was it this?

Only way to find out. Check the chain tensioner carefully as well. You will have to remove it to move the chain over the cam sprocket I suspect. I was having some issues with the cam sprocket moving ahead until I thought a foreign object. Might actually accomplish this.

It of course is possible the chain was put on wrong when it was installed. Although anyone that could change the chain should not have made that error. Yet you never know.

I never owned a 603 engine yet I think getting inside the oil pan is easy. I would tend to check in there if the engine is quieter at idle after the timing is corrected. Or back to what you remember. Finding anything it there would be a red flag over going right back into service. I also wondered if a ball bearing or part from their problematic vacuum pump might have transited up and over the cam sprocket in the chain. This could move the cam sprocket I suspect. I would remove the vacuum pump and check it before starting the engine again as a priority.

Other approaches will vary. Remember I am not a working mechanic. I only try to express what I would do. At the same time if you have lost a ball bearing out of your vacuum pump or more. You are a lucky person. The original vacuum pumps with no bolt heads on the front can create real issues with these engines. Personally again I would not run this engine at all until the vacuum pump is checked. If it has lost some of the ball bearings it also could be a new noise. Although I do not really know that. It is wise to find a vacuum pump anyways that does not have a smooth face. They have sealed bearings. The original ones are not to be trusted. Perhaps I am too cautious. Being as old as I have become.