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  #1  
Old 01-02-2016, 08:59 PM
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om617 spun rod bearing - rebuild or replace?

I bought a manual 1980 240d recently with knowledge that the engine "had a severe knock." The owner had performed an engine swap by putting in in a 1982 617 turbodiesel.i believe he cut the driveshaft himself and if i remember correctly he said he rebalanced the flywheel? is that a thing with this engine swap?

He sold the car to a man who abused it. one day he filled it with petrol and i think drove it on petrol for at least a little while. thats when he gave it back to the previous owner. the knock from a spun rod bearing on cylinder 4 was present the day he gave it back to the previous owner.

I don't know what I should do. Is it unreasonable to swap in a used crankshaft and rod, replace piston rings and bearings and then drive away? how can i tell exactly if my block is still useable?

my options are: buy a running 300d so i can verify the engines health. this will cost about $1000 give or take, plus any machining costs (wont i have to rebalance something? help me please lol).

option 2 is replacing it with an entire pick n pull engine. i dont know how expensive this will be or what costs will be associated with going this route..

option 3 is keep my block and just replace the broken parts, plus refresh the engine like the seals the bearings the piston rings etc. my engine-savvy friend acts like it will be simple but he has admittedly not worked on diesel engines. a couple people online (benzworld) have told me its not so simple as to just replace the broken bits with these engines.

so what is entailed exactly with rebuilding one of these engines? how do i know if i should keep the block i have or replace it entirely? what would you do?
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  #2  
Old 01-02-2016, 09:34 PM
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Ouch...

A rebuild is probably out of the question, though it has been done.

Depending on where you are located, a PNP engine may or may not be feasible. It's certainly possible to get a good engine that way, but you run the risk of getting an engine not a lot different than the one you've got.

The best course of action would probably be to get a running car with an engine you can hear run and evaluate.

In my own situation I got a running, but thrashed 300D for $700 which provided the donor engine/transmission for my SL swap. It's got nearly 100k on it since the swap so it was a good one. On the other hand I got what was supposed to be a good "spare" engine and transmission from a PNP and even though it ran, closer inspection showed the head was cracked and the pistons were trashed from melted prechamber balls. The good news is I only paid $400 for the thing and used the transmission when the original one failed.

There's no one good answer but there are options.

Here's a quick sample of what you might find for well under a grand based on a 30 second search in my area - http://sandiego.craigslist.org/nsd/cto/5382333622.html
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Old 01-02-2016, 11:23 PM
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You don't mention where you live, so members nearby can chime in.
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Old 01-02-2016, 11:31 PM
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Ran on gasoline. Nah, don't even try to save that engine.

I vote for a verified good runner. You couldn't even get a good engine with fuel issues because you need to declare your existing fuel system wasted by the gasoline.
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Old 01-03-2016, 03:00 AM
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Is it confirmed its a rod-bearing...?

Maybe the petrol has stuffed up an injector...

A bad injector can make a terrible knock on one cylinder....

The use of petrol by mistake does not necessarily wreck an old 617--Even if driven for a few days. Usual issues are vapour locking and the car stopping when its fully warmed up.

Apart from possible damage to the injection-pump, (You'll know about that PDQ) the engine itself wont care much about some petrol in the fuel, although the additives in the petrol could dislodge crud and make an injector spray-pattern crappy, leading to a combustion-knock very akin to a failed rod bearing.

--This is through Experience--And Not Anecdotal Evidence like many spout about mis-fuelling cars....

Thing with mis-fuelling, Garages rub their hands with glee at the sound of it, saying Everything needs replacing, pumps, injectors fuel-lines--you name it, even if the car is still running hence promoting the notion of death by wrong fuel!
--When all they (Usually do to repair) is to replace the fuel and the fuel-filters!

If it were me buying it, and I could confirm its Not a bearing I would happily buy it, I wouldn't give the petrol thing a second thought.
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Last edited by Alastair; 01-03-2016 at 03:15 AM.
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  #6  
Old 01-03-2016, 03:57 AM
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Quote:
Originally Posted by vstech View Post
You don't mention where you live, so members nearby can chime in.
good point! im from northern california, about halfway between SF and Sacramento. im familiar with the craigslist markets but yeah if anyone has another om617 engine i might be interested in purchasing it.

also yes i have confirmed its a spun rod bearing on 4. theres also wear on the rod bearing on 5 and on the crankshaft. anyways im pretty much ready to start shopping for a running car..and the only thing im really interested in is the engine. so how can i evaluate the health of the engine while im shopping? test driving it obviously be involved, but ive never driven one of these cars. i probably wouldn't be able to tell if there was something subtle wrong with the engine.
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  #7  
Old 01-03-2016, 08:36 AM
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I guess it is not impossible for using Gasoline to cuase a spun bearing all of the Diesles I have see where that has been done it usually damages the Injectors and when it gets noisy enought from that they stop driving it.

I suppose there could be combustion chamber and head damage. However, you won't know till you take the Enginen apart.
Sometimes you can tell a rod bearing if the cylinder head is off and you rotate the engine and you see that the piston remains stationary for bit (don't do that at tope dead center) till the clearance is taken up. I don't know if that can be easly seen if you pulled a Precombustion Chamber.

You are not supposed to do it but mobine the Crank shaft back and forth would show if the pistion is stationary during part of the rotation (don't do that at tope dead center).

If it was previously an Engine that had an automatic transmission on it that explains the previous owner balancing a manual flywheel. I think that would complicate an used cranksaft swap unless it turns out both flywheels are neutrally balanced.
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Old 01-03-2016, 09:33 AM
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Good running used engines are too easy to come by for me to put much work into an existing engine unless the rest of the car was outstanding and I wanted to bring the engine up to specs and keep the car. I would find an engine, replace all of the easy seals down to the manifold gaskets and install. That would be a good time to deal with any transmission leaks, B2 or anything else you can think of.
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Old 01-03-2016, 12:17 PM
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I see good engines frequently in PnP junkyards,given these aren't the hardest engines to remove.And the fact that you can get a year warranty for an extra $50 or so,it's worth a shot! Plus you could get one on a half off for really cheap,just food for thought.

You could get a engine with a year warranty for $160 on a half off at our local PnP.. Full price would be $260ish,these engines don't commonly fail and are very stout,you're chances are pretty good at finding a good one. You can pull the pan off there at the yard to inspect the bottom end too

Last edited by mbolton1990; 01-03-2016 at 02:14 PM.
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Old 01-03-2016, 02:38 PM
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I'll agree that the PnP is probably the best option. I was lucky and found a running car for $900 and got $ several hundred back by selling leftover parts that I didn't need. I'd suggest that you run a compression test on the potential donor so you avoid a total bummer (you may need to take a battery and jumpers to do that) and you might even get it to start for a minute (they usually drain the tank but the fuel filter holds enough for it to run for a few minutes). Ideally you could run the glow plugs and do a proper start but if necessary a squirt of WD40 or even a SMALL amount of starter fluid can at least get it running so you know if it works.

Harbor Freight has a Diesel compression tester that fits in the glow plug holes and it's pretty cheap - well worth having. Seems like mine was $35 or so on sale.

Most OM617s are in pretty good shape unless they've been totally abused. My guess is that if the rod bearings were taken out by running on gasoline they were pretty questionable in the first place. Remember, failure of oil pressure (or a bazillion miles) is pretty much required to destroy bearings and having the engine run on gas has nothing to do with the engine making oil pressure. Even if the engine has a lot of blow-by (combustion gasses sneaking past the rings) it would take quite a while for enough gas to enter the pan to dilute the oil enough to cause real damage. What I'm guessing is that the engine was "iffy" in the first place and the intermediate user beat the snot out of it which caused a marginal bearing to take a hike.

Pull the dipstick on the potential donor, look at the condition of the oil (Diesel oil often gets black but that isn't necessarily a terrible thing) and smell it for fuel or coolant (sweet) smell which gives a clue about blow-by and maybe coolant in the oil - pass that one by if either is present. Pull the radiator cap (Guys - am I remembering correctly that Mercedes HAVE a radiator cap? The Volvo didn't) and see if there is a foamy-looking substance. That's an indication of oil in the coolant - another reason to take a pass.

On the balance thing: I'm running a OM617 with an aluminum case Getrag 4 speed ('84 240D manual), along with the clutch and flywheel from the 240D. I simply bolted the whole deal up and went for it - and all is fine. My guess is that the builder (thru unknown methods) balanced the driveshaft which would probably need doing. Remember that if you get the whole deal back together and it shakes you can book time with a local industrial balancing company and they can balance it in the car and running. They fit the car with an accelerometer system and measure the point of imbalance and the amount and they'll add weights as needed to fix it - it's not rocket surgery. No idea of cost in your area.

Dan

Last edited by Dan Stokes; 01-03-2016 at 07:01 PM.
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Old 01-04-2016, 12:52 PM
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Quote:
Originally Posted by Junkman View Post
Good running used engines are too easy to come by for me to put much work into an existing engine unless the rest of the car was outstanding and I wanted to bring the engine up to specs and keep the car. I would find an engine, replace all of the easy seals down to the manifold gaskets and install. That would be a good time to deal with any transmission leaks, B2 or anything else you can think of.
For myself I find removing 2 Engines quite a bit of work.

Pulling an Engine at home is way easier then doing it at the Junk Yard. And, at the Junk Yard you are pulling out an unknow Engine.

If you get the Insurance that covers the J Yard Engine but not the Labor of pulling the J Yard Engine you just installed out if it has a problem or the labor of pulling another J Yard Engine to replace the first J Yard Engine.

My Wife overheatd My Van Engine (she did not notice the Water Pump was leaking and thought the Coolant smell was gasoline) and it ruined the Crank and A Rod with some minimal socoring of the Cylinders that honed out OK. But, I chose to pull the Engine and actually take a look at what was wrong before I decided. And that is what I liked to do before making a decision.
Note that if I intended to keep the Van the Engine had to come out reguardless if I was going to swap in another Engine or not. It was not much extra labor once the Engine was out to find out what was wrong with it.

So I got another Crank, Rod, Ring Set and new Bearings and timing Chain (which was worn out). So with a little extra labor I have a mostly rebuilt short block that ought to last for a long time.

Also it is a more of a pain to remove an Engine from the Van then in a Car.
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Old 01-04-2016, 01:22 PM
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The Mercedes engines are about as easy to pull as any engine in the world. You don't even have to remove the hood! The car should be up on stands in the yard so it's pretty easy to pull the bottom stuff - though I agree that it's a ton easier at home - I have a hoist. I did mine in 3 hours at home and I'd guess that would take 4-6 hours in the yard.

While I'd agree that pulling an engine at a salvage yard is somewhat of a chance I still think it's your best bet given the tough nature of these engines. Just do the most thorough check you can before you pull it.

Dan
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Old 01-04-2016, 01:48 PM
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In the yards out here there are guys that hang around looking for work pulling stuff. Pulling an engine is probably on the order of $100 or maybe even less.
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Old 01-04-2016, 02:24 PM
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Measure compression in each cylinder before deciding. I don't think a spun bearing would keep you from making that test, though the extra gap might give a low reading on that cylinder. If so, a "leak-down" test would tell if the cylinder rings still seal well.

If the compression is excellent, it wouldn't be terribly hard to repair the engine. You would have to remove it and remove the head and upper oil pan. You can probably slide the crank off the timing sprocket. Remove the tensioner first for clearance, plus its spring probably is worn ($7). Wire-tie the timing chain to both sprockets so you don't lose timing. Change the rear oil seal while in there. Consider a valve job while the head is off.

When my 1985 300D engine failed, I lucked out and bought a used engine off craigslist for $300 + starter. Turned out perfect (<400 psig all cyl) and looked like a recent rebuild (fresh paint mark on camshaft). I started rebuilding my original engine. So far installed new cylinder liners but no machine shop yet. Haven't searched for someone who can rework the head and test sealing (w/ pre-chambers sticking out).

Re sourcing a crankshaft, I recall buying a set of used turbo pistons from Rollguy here. He has taken many engines apart so might have something. Shipping is $$$, but if you wait until your next SoCal visit could save a lot.
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Old 01-04-2016, 05:43 PM
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I think it's highly unlikely that the gasoline had anything to do with the rod bearing failure. The guy who put gasoline in it probably didn't check the oil and ran it low or out which caused the bearing failure. Someone who puts gasoline in a diesel probably doesn't know how to or care to check fluids.

Gasoline is a solvent, unlike diesel (a very thin oil). When gasoline is put straight into the fuel system, it washes away all the diesel and provides very little lubrication. That spells death for the elements in the injection pump. When it gets to the injectors, it causes wear in the body like in the pump elements, but it also melts the nozzle pintle off of the nozzle and erodes the spray hole to a larger size. Small quantities of gas are acceptable and even recommended for extremely cold weather starting, but straight gas kills engines quick.

The abuse, the gasoline, and the questionable history all make me say ditch the engine and get a known good runner. Drain the tank while you're at it.
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