216K miles. Purchased recently.
First Mercedes.
Previous owner was told intermittent rough idle, hard starts and no hot start condition was due to leaking head gasket and possible burnt valves.

Only smoked during rough idle, no oil or coolant mixing, no oil or coolant usage.
Would run great about half the time.
Sounded more like an electrical problem or sensor issue to me, so I started trying to trouble shoot the problem before taking it to a shop for a head gasket and valve job.

Cleaned engine, changed oil and air filters. Found a large amount of sludge in the filter and started Auto-rx treatment. No significant improvement yet. Only two hundred miles into the program.

Reconnected two broken vacuum lines. Slight improvement

Changed out Crankshaft and Camshaft Position Sensors. No significant improvement.

When changing out the distributor cap and rotors, observed cracking at mounting screws and significant corrosion on passenger side and broken static guard on driver side.
Plug wires were dry and and some cracking evident. Plug wire on number one cylinder was extremely corroded and plug wire on number two cylinder was half corroded.
Bakelite boot on number four cylinder was broken.
Plugs showed normal burn, but gaps were excessive.

Changed out Cap, rotors, static guards, wires, and plugs. Big improvement.

From what I can surmise, when the upper radiator hose blew out, coolant leaked on the passenger side distributor and valve cover.
Judging from the corrosion pattern, it seeped into the number one and number two spark plug wells.

Still to go:
Replacement of some vacuum elbows and lines.
Serpentine Belt.
Fuel System Treatment and fuel filter.
Finish out Auto-RX treatment.
Change oil pressure sensor.
Change or repair retractable antenna.
CD Changer.
Cup holders.
Front seat repair.
Squeaks and rattles.

Some newbie notes:

Since I had current subscriptions on Alldata, I added one for this car as well.
I also purchased the WIS and Parts DVD from MBUSA.
The information on alldata and WIS are pretty much the same and are lacking in some of the more helpful information.
The Parts DVD was helpful but somewhat difficult to use.
Both the WIS and Parts DVD were dated in terms of integration and user interface functionality.
They are also difficult to install since they appear to be a copy of the dealership programs.

A lot of the bolts were metric hex and difficult to access with a 3/8 drive metric hex socket set. I need to get a 1/4 set and a serpentine extension or cut down the shaft length on the 3/8 drive set.

Changing the spark plug wires was one of the more puzzling items.
I had to remove the rear wire harness bracket on the passenger side and loosen the vacuum line, camshaft position wire and power steering pump bracket on the drivers side to route the plug wires.
Before starting, I took notes and pictures on the routing on the wire trays.
If you clean the bottom of the wire trays, there are small numbers molded into the plastic to identify which wires go in each slot.
I never figured out how to fully remove the bottom plastic coil wire cover and ended up changing the coil wire with it in place.

Mercedes parts are expensive.
Even more so than Land Rover.
On the other hand, the parts are well identified and engineered.
Going into this, I was under the mistaken impression that a rebuilt engine could be had for a reasonable price.
I was shocked to learn that a rebuilt long block M119 was in the $7-9K range with a core exchange.
Twice what I paid for the car to begin with.

All in all, I like the way this car feels on the road.
I only have a few hundred miles on it, but it is really a nice smooth solid ride.
On the highway, there is a feel of unlimited power.
My wife and daughters love it and are hashing out which one gets to be the primary driver.

Hopefully someone will find some useful information from this post.
Thanks to all the advice and previous posters.
It looks like I may have dodged a bullet on this go round.

Thanks for taking the time to post this. I've got a 92 400E that runs perfectly, but your experience may come in handy for me in the future. From what I've seen in your post and another it would seem the 119 has an appetite for dist caps and rotors, not something I've seen before, but I've more experience with German cars from another town.

__________________
Fourings

84 Audi Coupe GT with Turbo engine, EFI (buh-bye CIS), Jamex seats, Koni's/H&R's, e-code lights. 210k and counting.
1992 Anthracite 400E, 161k, "Grey Ghost".
1986 VW Quantum Syncro, 192k, gone to the crusher in the sky.
1989 300TE 172k. (Was mine, now also Mom's car)
72 280SE 4.5 (Mom's car)

sifd324,

Be patient it takes miles Auto-Rx will work I have used it for 4 years. With 216k miles are you going to do 2 or three cleaning and rinse phases good luck.

Daryl Baines