"new" w123 240D... - PeachParts Mercedes-Benz Forum

davestlouis · #1 12-26-2005, 03:46 PM

I just saw a broken-down W123 on the side of I-370 in St. Louis this PM...left a note that I'd like to buy it...the kids called back, said it had been low on oil , started knocking, so he shut it down. I offered $500 and I'd get it towed. Looks like a deal. Now, if it really was knocking, is the motor toast, or is there any purpose in taking it apart? I can get my mitts on a 240D parts car for about $250 with a good motor, but I'll have to pay to have it swapped over. Any thoughts? BTW, it's sort of a tangerine color, with tan MBtex, 4 speed and a sunroof, steel wheels with 4 good color-coded MB wheel covers and whitewall radials.

Ralph69220d · #2 12-28-2005, 11:49 AM

Hard to say how quick the driver pulled over and shut down or whether it seized. If it seized I would think you need to replace crank and rods, though I defer to Pro MB techs on this site. The valve train is going to lose it's oil supply first so possibly some damage there. Personally, I'd look at it as a complete engine rebuild if you're doing it yourself; you've already got the head off and rods disconnected so may as well replace rings and possibly pistons while you're at it and have the head worked over professionally. If it starts and the rods don't knock maybe you still might have a decent engine, though at least some damage must have occurred to the crank and rod journals. If the kid let it run that low on oil then I would think he had not maintained it well in general (e.g. few or no oil changes, etc.) Hope the bottom end is still serviceable for you and you have nice car.

rg2098 · #3 12-28-2005, 12:14 PM

Count on getting that parts car and having the engine swaped if I was you. Never trust what the PO said. Your engine is most likely shot.

diametricalbenz · #4 12-28-2005, 02:58 PM

As a side note check to see if both cars are 77-79 or 79 1/2 to 83. I just dropped a nice 81 engine into a 1979 body but had to change the exhaust manifold and intake because the A/C line wouldn't fit. The throttle linkages are also different so that may take some toying with to get it right. There is also the York or R4 issue as well. There are always surprises when it comes to swapping anything but that's the fun of it all.

davestlouis · #5 12-28-2005, 10:42 PM

Well, I got the car today, it started 3rd try...40 degrees outside, stumbled and vibrated for 30 sec or so, had good oil pressure the whole time. As it warmed, it ran smoother and I drove it around...I've never had a diesel before, and I don't really know what it's supposed to sound like. There is a knocking noise, that really doesn't sound good, knocking increases in frequency with higher RPM's. Clearly not a good sign, but I wonder how bad it is. As an aside, the maintenance book suggests that the car came from Syracuse NY, was serviced at several places there, through 167xxx miles in 1996. It is now showing 205xxx and I have no records since the mid 90's. Where should I start with this motor?

Mark DiSilvestro · #6 12-28-2005, 10:57 PM

I presume the oil has now been changed or at least topped off. There can be other reasons for excessive diesel knock, including a malfunctioning or mistimed diesel injection pump. Before condemning the engine,
I'd see what the oil pressure reads as the engine warms up. Fully warmed up, the oil pressure guage should easily reach max at any speed significantly above idle.

Happy Motoring, Mark

davestlouis · #7 12-28-2005, 11:18 PM

the oil is filthy but full, and it ran with the gauge at "3" under load, falling to "1.5" or so at idle...I kept driving, but the temp gauge must be dead, never went above the bottom

davestlouis · #8 12-28-2005, 11:18 PM

smoked under load when cold, no visible exhaust after that

Mark DiSilvestro · #9 12-28-2005, 11:28 PM

Change the oil & filter. Put in some 15W40 Delvac or Rotella. Maybe you can save that engine or at least buy some time. If you're serious about keeping this one going, that $250 parts car does sound tempting, if you have a place to store it until you need it.

Happy Motoring, Mark

davestlouis · #10 12-28-2005, 11:41 PM

I'll change the oil this weekend and see what develops...this car is like an ugly stray dog, I feel sorry for it. The parts car is about the rustiest car I've ever seen, but is reportedly mechanically sound. Let's call the oil change step one, whwat's setp 2,3,4, etc? What's a logical order to do things?

Mark DiSilvestro · #11 12-28-2005, 11:59 PM

I'd be concerned about the temp guage (or maybe the thermostat is stuck open and it's just not warming up)
What about the heater? If it's putting out plenty of heat, there probably is a guage malfunction. Make sure the coolant is circulating and maybe check the temp with one of those dial guages you stick in the radiator neck. If the coolant's filthy, change it too.

Happy Motoring, Mark

davestlouis · #12 12-28-2005, 11:59 PM

BTW, it's a 1983, so strictly speaking it doesn't belong in the vintage forum, but I think of all 123's as vintage. It has a sunroof, power windows, and NO TACH. Who in hell would make a manual-transmission car with no tach? The parking brake also just barely engages, any trick to adjusting it?

davestlouis · #13 12-29-2005, 12:01 AM

Mark, there is no heat, largely because the blower motor doesn't run, but it never did feel warm at all...my W126 throws some warm air at the windshield base even when the blower motor fuse is blown, for the 20th time. I found a receipt for belts from 6 months ago, and the indicated mileage has only changed 2k since then. I wonder how much this little beast has been getting driven lately.

pj67coll · #14 12-29-2005, 03:29 AM

You seem to have a lot more luck than me Dave. Where are all these discarded diamonds in the rough when I'm trying to find one? One thing I'll comment on. I drove mostly stick shift cars for the first five years or so of my driving life and none of them ever had a tach. Never really understood why people in the US are so insistent about tachs. If you cant change gear from the sound of the engine you shouldnt be driving.

- Peter.

Mark DiSilvestro · #15 12-29-2005, 09:09 AM

Supposedy, sometime in the late '50s, a Mercedes spokesman was asked why they didn't offer options commonly found on American luxury cars, such as power windows.
The response "If you can't roll down the windows, you shouldn't be driving!"

Except for sportscars, tachs weren't commonly found in stickshift cars until the early '80s. Now most cars have one. I learned to shift without a tach and never had one until I bought an '87 Isuzu Pickup. Even my automatic Nissan has one. I only use it to monitor my highway revs.

Happy Motoring, Mark