I just bought a 240D. What now?
 

I just bought an '83 240D with 128,000 miles. It's in pretty good shape for its age. It does have a very rough idle, but smooths right out when it's in gear and moving. That may be caused by a bad drivers side motor mount. I do have a parts car as part of the deal.



My hobby is fixing old diesel machines. In addition to the stuff in my signature, I have had VW diesels in the past, and have some little Lister generators now.


My questions are: what should I know about this machine besides ``look for vacuum leaks?''


*Where can I find manuals? What manuals should I get?

*Are there any special tools that are must-haves?
*Are there any parts that I should keep on the shelf, other than consumables like filters and glow plugs?

*Are there any problems that are sure to be there, anything that's going to bite me if I don't address it?
*What else should I ask you all?

Sounds like you got a good one. Got my 1980 240D off a local who volunteered at our food bank. His toys: vintage American (58Pontiac) and the Benz. for 16 years, he paid dealer or Indy to svc/repair til had multiple probs, sold to me for $1000: Here's what I did in 1st year. New: all fluids/filters, all 4 rubber brake lines, alternater/battery, new tires, rear sway bar links, manual transmission mount, flex disks, steering damper. + detail inside/out. Was a great little car, engine had blow by, but didn't use oil or drip during normal driving. After few years, replaced rear CV axles with aftermarket and sold it when got my W211 wagon. Don

For a manual, I had an old Haynes 300 diesel manual from other W123's I had over years. Pretty useful for NA W123, not so much on W126, but helped when I rebuilt a 300SD engine and still avail cheap on eBay. Don

Rough idle may mean needs a valve adjustment.

Congrats! 128k miles is nothing, though if youre in Alaska, not sure how that climate takes its toll.

My 240D also has a rough idle when in gear with AC on. The tiniest bit of throttle makes it smooth, and its as enjoyable around town cruising car as I can think of - its just so smooth and nice to drive in those conditions (before the engine goes too high in RPMS, and gets sort of raucous).

IMO, the best thing to do first is to rebaseline the vehicle. This means all fluids:
- Oil + Filter
- PS Fluid + Filter
- ATF + Filter
- G-05 Coolant
- 75w-90 Differential Oil
- DOT4 Brake Fluid

And Id say that you need a valve cover gasket, new belts, new brake hoses, and an ATF filter kit. Also clean the grounds, between battery to chassis, and engine to chassis). That should get you in a pretty good place for a driveable car, assuming there isnt another set of issues that drive other repairs.

Vacuum leaks can be a concern for locking, engine shutoff, and AT shifting. You may care, or may not (e.g. operate locks manually, and have an MT car). For the rough idle, check your speed. They sell cheap non-contact tachometers. I need to buy and use one... Changing idle is easy. Also verify that your idle control knob/cable is working. It is likely that your engine mounts, subframe mounts, and possibly other items (transmission mounts, flex discs, diff mount, etc.) are compressed, and will require replacement, but cross that bridge when you get there. Engine mounts are almost assured, IMO.

The beauty of these cars is that you can get the FSM online.

https://www.startekinfo.com/StarTek/doclist.jsp

You may or may not argue that valve adjusting wrenches are a must have tool. The diff needs a pretty beefy allen, and youll likely need a socketed one on a long breaker bar. To truly assess timing chain wear, you need a dial gauge. This is done when you're doing the valve adjustment... It can be roughly assessed through aligning the timing mark on the cam tower - lots of info on that here.

The question of other parts to keep kind of depends upon what the car may need, what may become NLA, etc. Id say a spare fuel filter or two in your trunk would be prudent. Some folks may keep belts too...

Did the odometer roll when the wheels rolled?

plugged fuel filters can cause rough idle too.

But then power would be low too, right?

I know my 240 will cruise at 75 MPH no problem - and it is surprisingly peppy for 67 HP... If raucous. But it will shake like a tractor at idle in gear with AC on if the idle is not bumped up a bit...

Valve adjustment and again in about 3k miles then every 12k. Check for timing chain stretch, adjust or replace if needed. Replace the braided injector fuel return hoses ASAP. Watch oil cooler lines for leaks and clearance from the V-belts.

Oil changes with C rated oil using Hengst, Mahle or Mann filter.

Run it briskly, especially uphills and let it coast in gear downhill exercising the piston rings, don't overheat it and it will run a LONG time.

Good luck!!!

Mechanical lifters, then?

I usually use Rotella T4 15W-40 for summer, Rotella T6 5W-40 for winter. It meets the CJ4 spec. Does that sound OK for this old engine?

Yes. Valve adjustment specs should be on a sticker underhood. Process is in the FSM. This why I recommended a new vc gasket and possibly the wrenches.

Perfect. Or 5w-40 year round if this car isn’t going to get a ton of use.

Technically, no lifters correct??? Just a rocker arm that pivots with the adjuster actually threaded onto the top of the valve stem.

Definitely not hydraulic.

You're oil selection is S U P E R B !

Drive on...

JHZR2, that's a good list for any new-to-me vehicle.

It's going to be a summer toy, so probably one oil change a year, so the synthetic oil is the way to go, just in case I need to start it in the winter. It is winterized, so I can plug it in.

It sounds as if I already have most of the tools I'll need.

I have to get an engine and transmission rebuilt and into my '94 crew cab this summer, so this will go on the back burner until fall. I have about three months before winter closes in again, and a lot of outside projects! This winter I'll get it into my shop for a weekend and change fluids, filters, belts, check and adjust valve timing, and so on. Then it will be ready to play next summer.