I admit the 603 has some good features. But... I just don't have a nice fuzzy feeling about mine the way I do the 617. The 603 seems so much harder to work on... crowded engine compartment comparatively... seems to me anyway... even if the 617 is smaller under the hood, more of what you actually need to DO to it can be done without so many scraped knuckles. Everything we have tried to do on the 603 that was a major repair has been a fight due to breaking/broken plastic pieces EVERYWHERE, no hand space, having to remove four things just to get to piece number 5... that darn crossover pipe... stuff like that. It's not that it's a terrible engine it's just... it seems more difficult to work on, more electronic (bad thing), and more finicky. Most of my problems (over 50% anyway) have been electronic, and the 617 has less electronics. The 606 is a lot more electronic, I realize that... but it's ten years younger too, which has to make it a LITTLE bit less problematic.

I'm not criticizing the 603 by design, necessarily. My personal example seems pretty unreliable and working on it is very frustrating because it's hard to get to what I need to get to, and it's so electronified that it's nearly impossible to trace some problems. (like my shutting off in traffic)

If you think your 603 is slow, your going to hate the 617!

If you want a fast car buy a gas MB. MB is good about that, if the diesel is to slow they make a number of 300hp+ V8's and V12's to chose from.;):D

I will say the new CDI's are pretty quick, lots of torque.

The turbo should spool at just over 2,000 rpm if under load. I haven't floored my car anytime within the past few months, and that includes hill climbs and merging onto the interstate from the onramps. Again I'm not saying my car is a dragstrip stud ... I'm just saying something sounds amiss with your experiences.

I've spoken to more than one mechanic who say the 87 300D is a really nice car. My regular mechanic has a fabulous reputation, he has been working on these cars for decades ... and he's never told me the 124 is "junk." He has said the 126 is certainly a better suspension ... much more robust and easier to work on. But he also said the 126 is better than the 123. And he's never said the 123 or 124 are by any means "junk." A 124 is a different style car ... it's a little more sporty and it's not as high-end as the S class. What do you expect? And if you want to talk about mechanics bashing cars ... ummm ... 350 engine ain't the princess in the royal court of MB motors. Personally I don't think that means it isn't worth having, if you like it. Like I said in my previous post ... it comes down to tolerating imperfections and working through the shortfalls, whether it's the prospect of a cracked head or the prospect of a bent rod. Any of these cars, when you buy one, you take a chance at certain flaws biting you in the behind. Find one where the good outweighs the bad, in your mind, and go with that. If that's the 350L for you, get one and enjoy it ... but I don't think there's a need to go quite so berserk on the 603/124.

I don't need top speed at all. I just need a little torque boost. If nothing else, the 617 will feel better to me because the turbo will actually work a little sooner. The best friend I keep quoting her 300SD in every post... I've been following her to places for years with the rest of the crowd. We both put our foot on the floor and she leaves me in the dust.

Attraction of the diesel was the racks-up-the-miles feature that the gassers can be made to display - but only some of them. That's part of why my 300SDL is such a disappointment.

In that case I've got low compression, blown turbo, or some other serious problem. If I didn't hit the floor on every on-ramp - even the downhill ones - I would get killed at the other end. Don't have to drive it that way in-town, but pretty much I live on country roads, and I go 2/3 of the way to full pedal just to get moving from a general old stop sign, no matter where I am. Not a fuel delivery/filter problem, that's about all I know.


I should mention that although it's a dog on most days, for some reason it does have the occasional good day when it feels almost like everybody else says it should. But then, the next day it's back to being almost dangerous. Some days I feel like (although I've never driven one) I could do better with a 240d 5 spd.

Have you worked on the overboost protection circuitry any? What it sounds like is 99% of the time you aren't getting any boost, and then every so often you are.

I couldn't even FIND the overboost stuff for the most part. My searches tend to just confuse me. If somebody knows where to start looking, and can say "put your finger on this hole and see if something reaches out and grabs it" then I can start diagnosing. I don't understand how half of it works. The oil leak concerns me more... it doesn't just pour oil out the turbo but it might as well. It comes out the crossover pipe... it tries to come out at the block off plate... it just drips and drizzles majorly out... I can't remember exactly. Somewhere on the pipes coming out of the turbo headed toward the engine. The piece of pipe that the EGR used to sit sort of over, is covered in oil now. Does this mean the turbo is shot? Seals or something?

How to rebuild?

Something is wrong with your car, because a properly tuned stock 603 is at least two seconds faster to 60 than a properly tuned 617. On a straight up race between a 300SD and an SDL the SDL should pull on the SD.

It sounds like your overboost line is plugged, or just no there. This is not the original engine right? So the whole system has probably been hacked by a third rate mechanic.

Buy the CD if you don't already have it and go through the whole system.

I have to admit the 87 300D I had was a blast to drive. It had lots of power and got good mpg's as well. The only other good things about it was the cruise and A/C worked. Everything else about it was a POS. It wasn't a good example and was pretty much falling apart when I got it. It probably wasn't very well maintained in its late life.
It was a PITA to work on. It sounded terrible when starting it up after it sat a few hours. It ran hot in traffic or going up hills.It's electronics were a nightmare. Maybe if I had a better example to start with I would have a better opinion of it.

Would pay my weight in gold for factory paper service manuals. Have the CDs but the pdfs are so blurry and so generic that I can't do much with it. Haven't found a vacuum diagram that matches my car yet. You are absolutely right about its being mechanic-ed on by someone who knows a lot about Benzes, to judge by his inventory.. but who doesn't even hesitate to cut corners.

Which line is the overboost line? That SD (stock) definitely outruns me. I don't top out as fast as she does but she can beat me to 60 with no trouble. Nice little cloud to enjoy, though, so it's worth it :D

It's not the original engine, when the car had 285,000 on it, the engine was put in that SUPPOSEDLY had 160 or 170 thousand on it, nobody really knows and I should have red-flagged that lack of records when I bought it. Oh well... but anyway, I have no idea the true mileage of the engine, but it's definitely not original and it definitely had some corners cut.

The 603 we had had plenty of torque. Floor the accelerator at low speed and i'd get a good shove to the back of my seat.

Handled better than the W123 too despite the extra weight. A bit more stiffly sprung perhaps.

The overboost stuff is somewhat easy to find, if it's actual there. Look at the ALDA, and look for a tube running over to the drivers side firewall, just in front of the wiper fluid resevoir ... the tube goes into the top of a boxy little thing affixed to the firewall (there's a photo of it in post #13 of the thread here ... http://www.peachparts.com/shopforum/showthread.php?t=174798 ) ... coming out of the bottom of the boxy thing (the overboost protection switch) is another tube that connects to the intake manifold. If none of that is there, that's a good starting place for what your problem is. If it is there, look at the lines ... if they're black, that's blocking your boost from signaling the ALDA to jack up the fuel to meet the increased air induction. If I had my camera I'd take some nice pics for you ... but it's with my dad on vacation, while I house-sit ...

I don't mean to hijack the thread here ... if you want more info, PM me and I'll do what I can (the overboost circuit is one of the few jobs I've done!).

Your oil leak ... wow, I'd say that's a much bigger problem ... and out of my league at this point ...

Actually I'm the original hijacker of this one, sorry :behead:

Will make a new list of problems and post it or PM a few of the 603 folks.

Can't get out to the car for a day or two probably, depends on what's going on around here. Will re-evaluate after I find that stuff.

Out of this hijack for the moment.

One thing to consider about the 603 is that it starts in 2nd gear. I may be wrong, but I believe the SD starts in 1st ... is that right? You can pop the 603 to first via either the kickdown switch OR you can put the shifter to "2" as you leave the line, then to 3, then back to 2, then to 3 and into drive (think that's the right pattern ... I never need to do it, so I'm not positive). Again, though, I almost never need the kickdown switch and I never put it in first manually. You should get decent torque without it.

It goes manually into first if you put the selector in "2" before you start moving. I do this just to GET it moving sometimes. Kickdown is used frequently as well.

Some days it drives almost like a normal car. That's the frustrating thing. But on its worst day at its worst moment, I have to do all these things just to get it to pull the "fairly steep" hill out of the parking lot. Esp. when the engine is not up to temp. It just almost won't even take itself up that hill if it's not happy.

Seems to be maybe getting a little worse. Think it's related to the ever-increasing oil leak through the turbo. Have gone from 1 quart in 5000 miles to at least two. Sometimes the low oil light is coming on after that 2nd quart at about 3 or 4 hundred miles before the next change, so I ignore it. (Check the stick)