Tell me about 1995 and later Mercedes diesels
 

I've owned a few 123 diesels, and maintain an OM617 in my sister's W126 300SD, but I know almost nothing about the later diesels. We have a '95 C280 and I've become somewhat interested in adding a late model diesel to the fleet. As tempting as a new E320 CDI is, that's a lot of cash to drop on a car. I was shown a 1995 E300 diesel recently that looked interesting, as well as a 99 E300.

First off, what's the technology behind the mid-90s diesels? I know that they aren't CDI engines, but what is electronic on them? Timing? Fuel Pump? Throttle? Emissions? Were there many year to year changes that make one desireable over another? Was the engine in the '87 W126 used much longer than 87?

Second, what types of problems do the later diesels face? I'm used to doing things like dealing with vacuum leaks/issues on the 617 and chasing air cleaners all over the engine. Are the "problems" with the later engines similar in frequency and severity? I like shutting the hood on my sister's 300SD and telling her to come back next year.

Thanks for any info you can share with me.

-Tad

Mercedes imported diesels into the USA until the '99 model year (not including the recent CDI's) and these were the last of the indirect injection engines. I've had my 96 E300D for almost 3 months now and I'm loving it, but the first thing I had to do on this car is have new front spring perches welded in due to rust. This is a fairly common problem on the W210 chassis (96-02 E-class) and Mercedes covered 50% of my expenses. But now I'm really enjoying the car and the OM606 engine is amazing, especially how smooth, quiet and clean it is. Starting in '98 these cars have a turbo which adds a lot of performance, but probably some added maintenance costs too.

The OM606 engine (which first showed up in the 95 E300D) is still mostly mechanical, though more advanced compared to its predecessors as it has twin camshafts and 4 valves per cylinder. Some of the things that used to be vacuum operated, like doors and fuel shutoff are now electronic. The idle control is electronic too. But the basics like timing, fuel pump and throttle are still mechanical, and EGR is still vacuum operated, at least on my model. These models also have a mass air flow sensor which fails occasionally, but I'm not sure if my car has it.

Overall I'd say and I'm sure most will agree that the older models are easier to maintain as most things on them are simpler and there's more space in the engine compartment. But that's not to say the newer models are unreliable, quite the contrary. It's just that when something breaks it will probably cost more to replace.

I moved from a '87 124-603 to a '97 210-606 recently, primarily for safety. Still have both and will sell one eventually. Have read that there were only 1500 '97 E300D's imported in the US, so used parts availability may be limited. The 210 body style is the safest car of its era- fatality wise- with dual front and side airbags. The '87 300D is 1-2 seconds faster 0-60 mph and more nimble. The non turbo '97 is much more refined. Greater passenger room, economy, creature comforts and safety are there, but with some tradeoffs including: rust problems and spring perch failures, short lived glowplugs and difficulty changing them, leaky fuel lines, multiple electronic brains that have been known to fail, and plastic gizmos holding mirrors and switches breaking with expensive consequences. The '97 has a 5 speed electronically controlled transmission and injection pump-I don't think these were on the '96.There are multiple sensors monitoring systems in the car with fault displays in the speedometer area. The intake manifold with the EGR valve pumping exhaust gases into it plugs up air flaps internally, so the EGR needs to be replumbed to fresh air. Transmission needs fluid changes, even though MBZ calls it "lifetime". Synthetic fluids throughout are a given. So far, in the absence of major problems, I'm really enjoying the E300D.

Even though the w210 was made during the cost cutting days, it is at least one of the safest and economical sedans around. I love driving mine so much that I've put just under 50K on my car since I bought it almost three years ago. I think that says alot. Overall with the engine and transmission combo, the car isn't quick off the line, but really smooth. Kinda unreal in comparison to the w123 that many are familiar with. I plan on doing the springs perches just for piece of mind, but haven't gotten to it yet. Since I've owned the car I still can't get over how cool this engine is running from a stand-still to redline up through the gears. For a diesel to rev over 5,000rpm and remain smooth.. WOW :sun_smile

I replaced a 91 300D that I absolutely loved because it was totaled in an accident. I replaced it with the 98 Turbo Diesel. What a difference. Peppy is an understatement. It accellerates rapidly, drives and rides great. The only thing nicer is the 05 CDI.

You are correct that starting in '97 these cars have a 5-speed electronically controlled transmission, but I'm pretty sure the injection pumps are mechanical even on the newer cars. Or what do you think is electronic on them, besides the fuel shutoff valve and idle control?

One of the first things I did on my car is clean those intake manifold flaps. I haven't replumbed my EGR and I don't think it's necessary (in fact you may fail your smog check inspection if you have to test), but it is good practice to clean those flaps every now and then.

DieselAddict,
I believe the level of fueling is controlled by the ECU brain, and determined by input from sensors. This is why the ECU of the '97 606 can be "chipped", i.e. artificially enhanced for greater performance.
No smog inspections are required in this corner of the state, so the EGR valve was "freshened" to help prevent sooting of the intake manifold. It's easily reversible though.

Nail on head. The mechanical IP is fueled via electric gizmo, pump and controlled by the ECM. The throttle linkage on the '97 and up E300's is 50% mechanical and 50% digital. There is a cable that runs through the firewall from the accelerator pedal up into the driver-side master cylinder region to a potentiameter. This potentiameter converts this input into a digital signal to the ECM, which then tells the electric gizmo on the back of the IP how much fuel to feed the IP.

With re-routing the EGR intake, it keeps the entire intake system clean and never requiring cleaning. Also, it does not throw a CEL!!!!
However the soot isn't as bad as the CCV vapors that are allowing into the intake manifold. This vapor with the soot from the EGR form the paste that causes problems and decreases air flow. I've run my CCV mod and EGR mod for 1.5 years with not a single issue or CEL for that matter.

I have a 95 E300D which I really like. You mentioned that you looked at both a 95 and a 99 E300D; the 95 models are much less expensive. I have 154K on my car now (only 1K miles until I can apply for my first mileage badge).

As with any car you want to buy, check over the records and see what needs to be done. Brakes, tires, shocks/struts, suspension links, new fuel lines, control arm bushings/ball joints, glow plugs can all add up quickly. But to me these are service items. All cars can be driven a million miles...just depends on how much money you want to throw at them.

As much as I like this car, I wish it has more power when I need it. I think my next car will be a 98 or 99 E300D. Or in 15 years, a 2005 CDI. But I want to get 200K miles out of this car first.