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  #1  
Old 11-03-2016, 03:02 PM
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Sad Update On 300TD Turbo

Some months ago I posted here asking for help getting this car running again. Long story short, I have a bad rod bearing. Not sure how bad it is yet or if I can just replace the one bearing and call it done, or will it need a bottom-end rebuild. If it is that latter I am not sure I can spend the time and I have nowhere to work on it anyhow.

I am really conflicted on this. On the one hand I would like to keep it and fix it when I am able to (have somewhere to work on it and my health will hold up on me) but on the other hand I just need a running car to use as a daily driver. Been looking longingly at the W123 and W124 turbodiesel coupe (300CD or 300CE), but alas I can't add to the livery without deleting something at the same time (the 300TD being the only obvious choice.)

Alternatively I could put it into storage for another day when I do have the ability to work on it. I really do like the car so this might be the preferred option.

Anyhow, just venting here. Not really asking anything.

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  #2  
Old 11-03-2016, 04:59 PM
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The idea of just replacing one bearing.... violates so many of the physics rules and usual machinist practices that I suggest you find a Haynes or MB FSM and do a lot of reading before you get too much farther....
Until you take it apart you really have no idea what your situation is.... for example... is your crank rod throw repairable ... that would normally be with the crank on a lathe...
You might should be checking for a used engine which you can insert .... as the very least to give you a chance to carefully rebuild this one .... IF you really want and can afford to....
The other question often overlooked.. WHAT caused this bearing to go out ?
If you can not find that ... you risk being back in the same condition very soon with your rebuilt engine..
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  #3  
Old 11-03-2016, 05:11 PM
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Your best option is likely just putting another engine in. Rebuilds are extremely expensive and difficult...it's not a small block Chevy or a VW engine.

Engines are still reasonably plentiful, though availability has declined significantly in the last 3-4 years. The rust belt is a good source as engines outlast bodies. An engine swap is relatively easy and you'll have a whole set of spare accessories (injector pump, turbo, alternator, injectors, PS pump, etc) to last you a long time.
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  #4  
Old 11-03-2016, 05:30 PM
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Originally Posted by mach4 View Post
Your best option is likely just putting another engine in. Rebuilds are extremely expensive and difficult...
Mach - That is route I went at one time. Found a couple of engines in the C$1200-C$1500 range. But engines out of old benzes are old I had the used engine rebuilt before installation. Cost me about C$7000 and that was 15 years ago! (My own engine was in bad shape after turbo blew pieces of itself into engine)

If he could find a low mileage used engine though, that might be a good route. But if not, putting that much money into a car that won't be worth much, even with newer engine, probably doesn't make sense.

Mind you, I have kept throwing money into my 300D - mostly paint, rust & body repairs since the engine swap. Still looks and runs great. But I love these old diesels!
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  #5  
Old 11-03-2016, 05:57 PM
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Darn if I can remember what I paid for my back-up engine from one of the guys here on the forum but I think it was $650. It's runs well though the compression is NOT top notch. Still, it ran well when he pulled it and I'd trust it for a DD. I plan to rebuild it (note that I didn't say "have it rebuilt") just 'cause it's for a race truck so it would be preferable to have everything up to scratch.

My point is that if you fish around a bit you can find a decent running 617 for not a ton of $$ that will get you back on the road. I'd expect that the average guy with a decent set of tools and a place to work (I know a guy who rented a storage place for a month for this sort of job) should be able to pull this off in a long weekend (Fri, Sat, Sun).

Dan
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  #6  
Old 11-03-2016, 06:27 PM
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Just for fun I did a quick check on our local CraigsList and found this



There are others in the $1000-$2000 but I can only upload one image from my iPad....
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Sad Update On 300TD Turbo-image.jpeg  
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  #7  
Old 11-03-2016, 07:12 PM
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Quote:
Originally Posted by Vikingdad View Post
I have a bad rod bearing. Not sure how bad it is yet or if I can just replace the one bearing and call it done, or will it need a bottom-end rebuild. If it is that latter I am not sure I can spend the time and I have nowhere to work on it anyhow.

How did you determine that there is a bad rod bearing and have you determined what cylinder contains the bad one?

Having rebuilt or repaired countless engines over the years I can offer this.

A connecting rod / main bearing insert needs a smooth round journal to ride on otherwise the new insert will have too much clearance / be damaged in short order. In other words, there are two mating parts to a bearing system, the crankshaft journal and bearing insert.

There is a third critical consideration, the bore that the bearing insert sits in. This is what keeps the bearing insert round and it's smaller ID relative the the insert OD will keep the bearing from rotating. In advanced stages the bearing looses radial tension and starts to spin in the bore causing wear.

On some engines ( in general not MB specific ) the bearings can be softer than the crankshaft surface. In that case changing worn bearing inserts can result in a lasting repair.

On other engines, the bearing is as hard or harder than the crankshaft. This results in a worn crankshaft journal that a new bearing insert won't fix.

If metal didn't travel through the oiling system, replacing the crankshaft / having it ground is a viable option. Some get all wound up about reusing parts at the limits of factory specs. Keeping very near factory specs for crankshaft bearing clearance is critical to a lasting repair. However piston to wall clearance / valve guide clearance can be on the high side and still be OK for general use, just don't expect the engine to last as long as a high dollar rebuild. This is called building a known good used engine when nothing reliable exist off the shelf.

Yes, for a common engine where quality pistons are sub $ 20 each, replacing them is the best route but an engine that has $ 200 pistons one begins to rationalize and factor in expected use the car will get and how long the body will last. I'm betting few would take their high mile running engine apart for a clearance check just in case something is out of spec.
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  #8  
Old 11-03-2016, 08:15 PM
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You're going to have a fine time finding a used TD 617 motor as they are relatively rare.

As you probably know, the wagon motor has a provision on the head for the SLS pump. However, you could buy a D engine and swap the head since you evidently have problems only in the bottom end. Get the head conditioned while it's off and you would be good to go.
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  #9  
Old 11-03-2016, 08:42 PM
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Here is a 617.952 down in Clovis, Ca. (Near Fresno)

https://fresno.craigslist.org/pts/5847927862.html

Keep poking around on CL for a 300D/TD/ or SD that has been wrecked, then at least you know it was a driver at the time.

Pull your wagon head and have it gone through.

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there were three HP ratings on the OM616...

1) Not much power
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Anyone that thinks a 240D is slow drives too fast.

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  #10  
Old 11-03-2016, 09:44 PM
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"Naturally Exasperated".

Nice.
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  #11  
Old 11-03-2016, 10:25 PM
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Originally Posted by Since66 View Post
"Naturally Exasperated".

Nice.
Not sure whether you're talking about yours or the one in the link above. The one above shows the turbo in the 3rd pic. would just swap that other in if it was decent. Go look, see it run, buy it, do a leak down test, replace gaskets except head gasket, install.

Make your trans leak free when it is out of the car.
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  #12  
Old 11-04-2016, 09:05 AM
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I agree w/97 SL320. More info on the bearing diagnosis is needed for an informed opinion regarding your engine. I have witnessed lots of engines eek out more years of service with just bearing replacement if there wasn't any other damage (ie: crank OK, just worn bearings). Plastigauge used properly is very useful in supplying hard data for accurate diagnosis regarding stretched/worn caps. Bearing replacement w/o major overhaul was a common repair into the 60s. As oil & filtration technology improved this repair became less common.
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  #13  
Old 11-07-2016, 03:56 PM
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Seems the #1 rod bearing could be easily replaced (maybe even #2), just by removing the lower oil pan. At least what I recall when I removed the oil pump in my 1984 300D (yes, possible but not easy), and probably must remove the pump to get at the rod. Any others require removing the upper oil pan, which means "engine out of car" unless someone was really clever. On U.S. engines, I have replaced both main and rod bearings from below w/ engine in car, but not so easy in our M-B engines.

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