OK you've changed the brake switch so you are good for a few years more!

Lets see, what else did I find when I first got the car?
I was hearing a clicking noise behind the dash as I drove and the key fob jiggled around, some electrical contact was intermittent. I was sweating it that the key circuit might have a bad flex cable or whatever is behind the dash and costs like getting two gold crowns if you need a replacement.
That may also be whats causing your problem related to key activation, if the key moves up and down excessively or feels loose I would tighten the collar. Or borrow that tool kit made for the purpose.

When I showed it to my mechanic friend at a local indy shop he came out with a box of key lock tools, including a special spanner wrench. He cranked on it a half turn or so and that fixed the problem. He said I dodged a bullet! I take that to mean these things are prone to giving problems.

The car came with an ugly spare key of some kind that looked like it was about to crack open (no chrome around it, just some cheap plastic) and the seller didn't have the official key, I decided to order a new one. That decision cost me nearly $250 (before a small discount for being a nuisance and asking for a discount since I knew the man in the office who was their wholesale account manager).

Then I found my front wheel bearings needed replacement. The steering had a lot of play in it, even after new ball joints and shocks. At 92K I found it unusual that the wheel bearings would be shot, but I guess if the PO had kept them tight (ok, back off 30-45 degrees) and not let them wear so loose they may have held up longer.
All in all its a real nice car now though!

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

My BIL has a ML320 that keeps flashing a warning or fault code. When read out it says something about the child seat sensor switch in the front passenger seat.
It seems either the switch is going bad or my theory is his teenage daugther likes to sit with her fannie at the front of the seat with no weight at the rear and that triggers off some inherent electronic watchdog that is intended to alert drivers from placing a baby carrier on the front seat!!!
Hows that for too much electronics? probaby only in CA cars. Maybe not maybe a NHTSA mandate?

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

DDH, thanks for the heads-up on the ignition switch mounting issue. I'll definitely check that out.

Ironically, my '98 has the SRS warning due to the seat sensor mat (with baby-seat monitoring) failing. That's a fairly common issue across the entire MBZ lineup of that vintage. More crap that, while it may sound (barely) useful for a tiny minority of owners, just adds unnecessary complexity IMHO. Yep, definitely becoming a Luddite.

Front wheel bearings on a w210 also seems to be a relative weakness based upon threads here over the years. A lot of people have fried their spindles because of it. Front bearings were never an issue on earlier MB's. Why? IDK. Maybe lesser materials spec'd for cost savings?

Remember when MB built cars to an engineering standard, then added a profit margin to the build costs to arrive at the price? Ever since Lexus showed up on the scene (and other Japanese cars invading the upper tiers) MB hasn't had the luxury of doing things that way. They had to learn to build to a price point, and it was a fairly steep learning curve for them. Sad, but true.

Older MB's (and 911's) were so overbuilt that you could constantly beat the living snot out of them and they didn't break. Hell, you could track a lot of them, and other than cooking the brake pads and shredding your tires, nothing mechanical would wear out or break. My '95 E300 has well over 400,000 miles on it and I drive it HARD, yet it just keeps going and going and going.

I'm stepping off the soap box now....

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Current rolling stock:
2001 E55 183,000+ Newest member of the fleet.
2002 E320 83,000 - The "cream-puff"!
1992 500E 217,000+
1995 E300D 412,000+
1998 E300D 155,000+
2001 E320 227,000+
2001 E320 Wagon, 177,000+

Prior MBZ’s:
1952 220 Cab A
1966 300SE
1971 280SE
1973 350SLC (euro)
1980 450SLC
1980 450SLC (#2)
1978 450SLC 5.0
1984 300D ~243,000 & fondly remembered
1993 500E - sorely missed.
1975 VW Scirocco w/ slightly de-tuned Super-Vee engine - Sold after 30+ years.

Maybe Chinese parts are involved? I know a shop that has a dislike for certain brake discs that came out of China, they tend to warp... I never had issues with Brembo or ATE etc. but now there are lots of aftermarket names, manufacturers I won't mention here for sake of brevity.
you said: My '95 E300 has well over 400,000 miles on it and I drive it HARD, yet it just keeps going and going and going.

Oh wow I have a lot to look forward to! I really like my '95 E320 wagon, its just a tad under 95K !!!
DDH

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

OMG, banish the thought of factory installed Chinese wheel bearings on an MB! Or maybe that's where MB sourced those soft intermediate shaft and idler sprockets on the M272 & M273 engines? (Just joking, of course. Sort of. )

I vividly remember when, of all suppliers, URO proudly announced that they were supplying MB with certain parts for older (w123?) vehicles that would be sold by MB dealers as factory replacement parts. IMHO, hell froze over that day. But I've taken this thread waaaay off course...

BTW, your '95 wagon is just barely broken in. Congrats on finding such a low mileage example. I don't know how old you are, but barring any accidents and with proper maintenance and a head gasket every 150,000 miles or so, that wagon may very well outlive you. Unless MB decides to have URO supply w124 parts in the future.

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Current rolling stock:
2001 E55 183,000+ Newest member of the fleet.
2002 E320 83,000 - The "cream-puff"!
1992 500E 217,000+
1995 E300D 412,000+
1998 E300D 155,000+
2001 E320 227,000+
2001 E320 Wagon, 177,000+

Prior MBZ’s:
1952 220 Cab A
1966 300SE
1971 280SE
1973 350SLC (euro)
1980 450SLC
1980 450SLC (#2)
1978 450SLC 5.0
1984 300D ~243,000 & fondly remembered
1993 500E - sorely missed.
1975 VW Scirocco w/ slightly de-tuned Super-Vee engine - Sold after 30+ years.

I made an error in stating the mileage on my wagon, its the 2000 E320 thats at 92K. The wagon was 120K when I got it about 2 years ago. Its nearly 140K now. So I may need a headgasket in a while? crapola.
I am currently fighting a problem with a Glow plug on the '99 E300D which was just reassembled after a valve job. Thats the subject of another thread but basically I found one of the cherished Beru GP's I ordered from Germany went DOA right away, maybe the same day all I know is its dead, Jim. (said Dr. Spock!)
I carried the injectors over to Gus and had them pop tested and all good so its going back together as soon as I get a replacement GP and probably will be a Bosch thats they stock locally.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

These are a few items that required attention on my 1999 diesel W210 which I bought new and drove as my daily driver until 2014. Sold it with 348,000 miles on it. Many people have already mentioned the rust problems with the problematic paint chemistry on '99 W210s. Won't spend more time on that.

Had a coolant pump impeller separate into multiple pieces. Replaced coolant pump. No more problem.

Both spring perches in the front suspension had to be replaced.

Front lower ball joints tended to wear out rather quickly

Had glow plugs shear off in the head.

Developed a clunk in the front suspension. Turned out to be worn end links on the stabilizer bar.

Brake light switch in the driver's footwell area failed. This caused a number of strange issues...don't recall all of the details.

The element came loose inside the trap oxidizer and caused an annoying rattle in the exhaust. Replaced the exhaust pipe with trap oxidizer and all was great.

As part of the glow plug problem noted above, I pulled the cylinder head to get the old plugs removed. While that was going on, I rolled in a new timing chain (this is a double chain). This was at 260k miles. The old chain was within one millimeter of being the identical length as the new chain. At least based on my data point of one old chain, these double chains do not stretch.

Car was great. It lived its first 348k miles of its life in NJ. It was washed religiously and the wheel wells rinsed, etc. In spite of this, the paint was losing the battle with rust.

Alternator failed one on a trip 500 miles from home. With the mechanical fuel pump I could drive it all day in daylight and waited to fix it once I got home.
Stayed over one night en route and got a jump start from AAA in the morning to complete the trip.

Fuel pump and turbo were rock solid. Never a problem.

I am not an aggressive driver but never got close to the 35MPG kind of fuel economy numbers I see posted by others. Occasionally in the summer on a long highway trip in hot weather I would get 30-31 MPG.

Now have my third diesel E-class. This one is a 2014 E250 4Matic. Now at 73k miles.

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2014 E250 Bluetec 4-Matic
2014 GL350 Bluetec 4-Matic
1996 Chevy Tahoe 4 x 4
2009 ML350 (sold)
2005 SLK350 (sold)
1999 E300 Turbodiesel (sold)
1998 ML320 (sold)
1991 300D 2.5 Turbodiesel (sold)