Loud Tapping, Rough Idle, Had to Tow
 

Last week my 1985 300CD wouldn't start. I determined it was the Neutral Safety Switch. Ive been starting it with a coat hanger, jumping it at the terminal near the battery to get around until I get a new NSS.

I was also chasing an oil leak yesterday and drained some of the oil because I found it was over-filled. I did a diesel purge at this point also to make sure it was healthy and nothing else went wrong in the meantime.

I went to drive it today and it started making a loud clicking noise from the engine and idling shaky. Also, the oil pressure gauge started trembling as it went up which has never happened before.
The clicking noise sounded like metal hitting the crank case from the inside, happens once each rotation (i watched the rotation inside the oil fill), and just gets faster with acceleration.

I tried driving the few miles back home but it persisted and even worsened to the point of it sounding like something metal being tossed around. I had it towed home.

I did a valve adjustment back at home but none were unusually over tight. It was unusually difficult to get the engine to turn over using the power steering bolt. The belt kept slipping on the crankshaft. (In the past the engine turned over more easily by hand.)

Still have to put the valve cover back on and see if its still tapping. Feels like Im in over my head here. What are the possibilities? Broken crankshaft? Chain tensioner spring? Injector? Alternator shaft bearing?

Plz help. Im definitely fearing the worst. How do I diagnose? :confused:

I have no idea what the issue could be. But to clarify. Are you saying that the problem occurred on the first drive after you drained oil out of it? By how much was it over full and are you sure you did not drain too much?

- Peter.

Pull off your Vacuum Pump and check the Lever and Bearing that are on it. Look where the long skiny Bolt goes through the Piston and see the Pison is cracked around where the Bolt is.

Check the face of the Timer for damage.

Drain the Oil and drop the small Oil Pan and see if there is fragements in the Oil Pan.

Check the Oil Pump Chain Tensioner Shoe, Spring and the little Snap
Ring that keeps the Shoe in place.

Look at as many Oil Spray Nozzles as you can see.

If it turns out to be the Vacuum Pump:My question What in particular causes vacuum pump failure?
http://www.peachparts.com/shopforum/diesel-discussion/204187-what-particular-causes-vacuum-pump-failure.html

Rough idle and tapping noises could be as simple as a bad injector. Any possibility you allowed some dirt or other contaminant into the fuel system?

Yes, I Diesel purged it with three cans, and 1 can of libro moly additive. The dip stick had oil about 1-2 inches above the top fill indentations. I drained about 2 QTs of oil with a Top-Sider. The dipstick was and is still a little over full but I left it.


I will check out the vacuum pump.

And also check out the oil pan for any broken parts.

What am I looking for on the Oil Pump Chain Tensioner Shoe, where are the spring and little Snap Ring? Where are the Oil Spray Nozzles and what am I looking for?


No, the injectors might be 30 years old. Definitely no dirt. Possibly age. I was very careful doing the purge which would have cleaned them anyway, right?


Im now dealing with the car not starting by jumping the starter with a coat hanger at the terminal by the battery. I cant test if the valve adjustment fixed the problem because It wont start. It just lazily turns over like a low battery but jumping the battery from another car didnt work either. Is my battery dead?

I now have to
A: figure out why it wont start now
B: Get a NSS which so far has been really difficult in my area.
C: test if the valve adjustment stopped the tap
D: Oil and filter change w/ pan off and check the pan for metal

Have the battery charged and load tested while you are looking into the vacuum pump. You may have several unrelated issues. Where are you located?

I just want to mention this SAFETY item...

by using that method to start the engine....

YOU ARE BYPASSING the neutral start switch...

so just make sure the car is IN NEUTRAL....
because if it starts in gear.... it will go forward or backwards ....
we have had two farmers killed by their tractors running over them due to this kind of mistake.... you would probably be beside the car...and not get hurt.. hopefully....

If it were the Vacuum Pump wouldn't I have no vacuum pressure?

Located a NSS and currently slow charging the battery. In SF Bay Area. It wont start with a jump. The battery is dated 12/12. Is the battery completely dead?

If only the Bearing is damaged there still might be enough movement of the Arm to create adequate Vacuum. Your Car Your call.

Question ask from Post 5. I can't remember the disopsiton of the Oil Pump Chain Tansioner stuff as it has been about 5 Years since I had the Oil Pan off. I only remember you can see it if the Pan is off.

Here is what was in the oil pan after removal. Small metal shards. This is pretty much everything that was in there shown on this towel which gives you an idea as to the quantity of metal shards.
Any idea what part these came off or what else to look at with the pan off?

Thanks for the input

Oil Pump Chain Tensioner, Spring and Shoe look good.
Oil Pump intake mesh filter has some shrapnel in it.

Will be dealing with the battery, letting it charge overnight, installing new NSS, and look in the Vacuum Pump tomorrow.

Strange how a bunch of seemingly unrelated things fail all at once.

Is the debris magnetic or not?

Could be bearing Babbit. Could also be vacuum pump material. I think you really ought to entertain Diesel911's suggestion.

It all stuck to this magnet (on a money clip) as seen in the photo.
What does this mean?
Rod Bearing Babbit is possible.
I was seeing discussion of this on this thread: LOUD engine knock - Remove oil pan with engine in car? 300D | Mercedes-Benz Club of America

If its a thrashed Rod Bearing am I out an engine?

Will definitely pull the Vacuum Pump tomorrow and entertain Diesel911's suggestion.

Yes, if the bearing is so far gone that it's shedding shavings of itself and creating a loud knock, the engine is no longer usable. :(

Rod Bearing Babbitt itself is not magnetic. I suppose that the part of the " insert ' that supports the Babbitt could be magnetic.... but I think there is too much mass shown to be that...
So I think you are looking at the vacuum pump ... lots in the archives about it imploding and putting major amounts of junk into the pan...
Can also be the chain mechanism for the oil pump drive...
At this point Diesel911 's suggestion is top of the list...

The oil level can get too high if the "lift pump" (below hand plunger) has a leaking seal thus letting diesel into the crankcase. That would dilute your oil and could cause wear & perhaps eventual failure of bearings and oil pump wear.

In most cars it is possible to replace the crank bearings with engine in car. You push the upper half around to get it out. Clean the gap w/ ethanol before sliding the new upper shell in. I tore apart my 1985 engine when it failed (pistons, not bearings) and don't recall the main bearings differing from my Chryslers (one of which I replaced main bearings from below). Rod bearings can always(?) be replaced from below, and usually fail before main bearings.

The problem on your engine is removing the upper oil pan to expose the crank. Search if anyone has managed to remove w/ engine in car (looks challenging). It doesn't use a gasket, rather a special "anerobic sealant" which is a type of superglue.

new developments:
here are pics of the Vacuum Pump

it appears fine to me?
im thinking its a chain/ oil pump part maybe as leathermang is suggesting?

looking into checking or replacing rod bearings with the engine on. not finding much info on this so far.

doesnt the crank case expose the crank? Im actually unclear, after removing the crank case during valve adjustment and removing the oil pan as to where the rod bearings are. Aside from Valve Adjustment procedure, Ive never had any other experience with working inside the engine.

If the shards are magnetic that will usually rule out bearing material. It has to be Iron.

That vacuum pump doesn't look like it grenaded. How does the timing device look behind the pump? The wavy drive piece should be smooth and intact.

If you can remove the upper oil pan with the engine in the car, you can inspect and replace the main and rod bearings. However, I don't think it's a bearing since the shards are magnetic.

Did the knock sound like it was coming from a particular spot, like up high in the head or down low by the crank?

pics of valve area.

The timing device looked ok behind the vacuum pump.

The tap sounded like it was coming from starboard side. Im assuming from the crank case. Pulling over it sounded like something banging around down into the oil pan.

I started it up again (before the tow) and it was apparently fine: no tap and no rough idle. Second time it was tapping again and shaking.

im debating at this point wether to close it up, try starting it, and listen where exactly its coming from.

Any good links on removing the upper oil pan? seems like I have nothing to lose at this point by pulling it off.

Does it sound like this?: http://m.youtube.com/watch?v=SogAyxDFDgo

The cause ends up being this: http://m.youtube.com/watch?v=IHm8OB9bcO8

If you don't mind a little mess, you can run it with the valve cover off to observe the valve train.

I have a feeling it's rod knock though.

yeah thats what it sounds like.

pretty resolved that its a rod bearing/ rod knock.

my question now is this:

are there any resources or links on pulling the upper oil pan and/or replacing rod bearings on a 617 with the block in the car?

e.g. is it possible to get the upper pan off? if so, can you access the rods and rod bearings from there? how many rods are there? how do you turn the crank to get to the different rods/ bearings? do they just pop out/in with a screwdriver?

too much iron in the oil pan, crank is a boat anchor. lucky the block did not self ventilate.

search for a new motor..

I agree with what you found in the pan, time to take up fishing, you have a great Boat Anchor. LOl.

Look for another engine, keep this one and tear it down to see what went wrong.

Found this link if you want to remove the upper pan w/o removing the engine from the vehicle.

Removal and installation of complete oil pan

I have removed the pan with the engine on a Stand, can`t imagine doing it
laying under the vehicle, at least on one of these MB`s.

Charlie

I vote no on both of these concepts...... Just no way to properly measure or check for damage caused by what has happened.... Twenty One to ONE compression ratio puts tremendous pressure on those rod bearings... how could that much torn up insert get to the oil pan with scaring the rod journal ?????? or perhaps the rod itself... ?????? and if you put a new rod in .... pretty much impossible due to not being able to pull the piston out the bottom... then it would not be the same weight as the others.... and doing this stuff upside down.... one needs to actually read the FSM to get an appreciation for the tightness of the parts put together in these engines...
Look for replacement engine... or take this one out and do the rebuild correctly on an engine stand with the FSM at your elbow all the time...

Assuming it is a bearing, is there a typical reason this occurs? Is there anything one should do to specifically avoid this problem? Or is regular maintenance the only preventative?

I definitely feel bad for the op. Good luck with a resolution.

The use of approved DIESEL OIL for the temperature ..... the regular changing of the oil and proper filters..

If you had a way..... the use of a preoiler like commercial engines use is very nice...makes sure your bearings have lubrication from rpm ONE and up.... as much of the wear on an engine happens in the time between start up and getting to working temperature.

I personally change to straight 40 wt oil after 100,000 miles on all my cars.. gas or diesel.... I am in a hot climate to I use a straight number.... those additives which make for multi viscosity ratings take away from the lubrication ability of the oil..... as evidenced by the fact that the worst running conditions.... a small gas air cooled engine... were always specified as needing STRAIGHT 30 wt oil.....

If it is the number one rod bearing. There is a chance the engine was run with low fuel pressure in the base of the injection pump for a long time.

Either still low or was. In my opinion it increases the loading on the first cylinders rod bearing. Enough to cause additional bearing wear on it compared to the others..

Not as big an issue as it is on the 616 engines.. Not changing fuel filters until they have been run somewhat restrictive for a long time is my thought on the usual causitive. Or a weak return spring in the relief valve as well or with the filters in combination.

The weaker lift pumps pressure output on the 616 engine compared to the 617 turbo engines may also be an additional contributor as well. It is hard to prove this other than the original thinking it was because. Being at the end of the lubrication chain of the rod bearings was the issue.

That it is more prevelant on the 616 engines to me eliminated the then original belief it was a lubrication issue.. I could still be wrong but suspect not.

This is reinforced by the wife not correcting my thoughts on this issue.:D
My additional belief that re kitting the lift pump and installing a pressure regulating spring from a 617 turbos pump in a 616 lift pump might be a good upgrade. If nothing else it will do no harm.

It took a lot of thought for me to arrive at this suspected conclusion with my small brain.Over time I have not observed anything new to lessen this belief. To the contrary everything I have noticed since tends to support my belief.

Hopefully by adjusting the fuel pressure to `19 pounds instead of the factory recommended 12- 14 pounds. May just with a little good luck shift the injection profile enough to equalise the wear by reduction of the loading on the first cylinder even a little more than normal.

Now this portion is just a totally unproven suposition. The problem with the fuel pressure is the effect it has is bad enough to actually be audiable. That was one of the principal reasons amoungst many that originally led me to my suspicion.

I do not want to come across as a parrot on this issue. Yet at the same time I think it is a very important part of a maintenance program on these engines that is not taken seriously enough.

For a 616 owner to ignore it especially Is a roll of the dice you should not take. You want to know what your fuel supply pressure is in the base of the injection pump. Seems to be somewhat less critical on the 5 cylinder 617s but still an issue with them at least my mind.

I really hope that some other theory will prove mine wrong. I do not always have to be right. Until then if you like it or not keep your fuel pressure in the base of the injection pump up where it belongs. The price of not doing so can be too high in comparison to the prevention. If I am right. Also your engine will run quieter on the highway.

I have two 240s. One was or seemed noisier on the highway. It had low fuel pressure. It seemed to quiet down at least a little after I got the low fuel pressure corrected.

I am aware of the issue of we wishfully want to believe something is now quieter. Several 617 owners have also reported the same effect.
They too may be delusional as well though.:rolleyes:

Fundementaly in a summer use car or where the temperatures will allow it. The use of straight 40 diesel oil is going to provide more wear protection. There are several common sense observations that actually prove it. I do not think having 100k miles aquired is a requirement to do it either.

I always thought that these engines should last longer than owners report. One problem is many may have already as so many odometers are not accurate.

Even as far north as the cooler east coast of Canada most old timers believe that anything less than 15-40 should not see regular service in older style diesel engines.Not changing the oil often enough is a really bad ideal on these high soot level generating engines. When the soot clumps it is abrasive in nature.

Barry has proposed this theory many times before...
there are no physics rules which agree with the idea that less fuel to the first cylinder would cause more pressure... none..
.... will elaborate if I get a chance.. but wanted to save this space next to his post..
Well, Barry posted fast enough that this is not next to his post...
but I appreciate the vote of confidence on the oil choice......

Hmmm, how long did you let it run when it was not tapping and the idle was smooth? Did you do anything different in the starting procedure, like push on the priming pump to prime the injection pump?

That metal may have been in there for years from some earlier malfunction, now corrected.

Give your experience level, I'd say button it all up and see how she runs. If you've still got the tap and rough idle, try ruling out a fuel issue (injectors or delivery valves). Send an oil sample to a lab for analysis - this will definitely tell you if the damage is recent or old news.

If you decide the engine has internal damage, I'd shop for a used engine that you can verify is in good running condition.

You mention in post #1.

quote:
I was also chasing an oil leak yesterday and drained some of the oil because I found it was over-filled.

First you have an oil leak, how bad and from where?

When was your last oil change?

How often did you have to add oil?

How often do you check the oil level?

About two weeks ago I checked the oil level in the 240, it was about 2 inches over full. Wiped off the stick and checked it again, Right at the full mark. HMMM that`s weard. next day the same, and since it has been at the full mark. This morning checked it for my Wife, and was right at the full mark.

My 85 300D did this too several times, really don`t know what causes this. and it doesn`t do it all the time.

Now maybe yours was doing this too, and then you drained the 2 or so qts?
I think with even 4 qts in the pan, the engine will still run w/o much trouble. though we or you don`t really know the amount of oil that was in there.
When you drained the pan, how much came out?

As Maxbumpo said, the debris in the pan may have been from a prior problem, and the pan was not cleaned out.

You did mention you heard some clanking and banging around in the engine, that isn`t a good indicator. :eek:

Charlie

When I first pull the dipstick out on my 240 it shows NO OIL ON IT...
my heart almost stopped the first time I saw that...
but if you put it back in you should get the true reading... it showed just right..'
and many have recommended that these cars be run with the engine oil showing half way between High and Low on the dipstick...... over that can cause oil burning for some reason... does with mine..
AND something to check.... the COLOR of your dipstick has to be correct for YOUR engine.... we have had people find it was the wrong color... and thus length...

Valve cover is on top of the engine, that is what you removed to get to the valves and the timing chain.

If you consider the engine as layers of sandwich:
Valve cover
Valve cover gasket
Head (contains valves, camshaft)
Head gasket
Block (contains pistons, rods, crankshaft, oil pump)
Oil pan gasket
Upper oil pan
Lower oil pan gasket
Lower oil pan.

You would need to remove the upper oil pan to get to the crankshaft and rod bearings.

Not a dog with a bone syndrome. I am wide open to others thoughts. My thought is rather than differant amounts of fuel fill and that is probably occuring. The principal suspicion is the sequential timing is changed as any element with getting less fuel.The injector will open later than by design.

The lift pump is a constant pressure type but at the same time only recharges once per injection pump revolution. Filling the later elements in a a really low fuel pressure initial setup may mean they are almost scavaging from the decreasing low pressure profile.

Since the relief valve is no longer functional. There is nothing to provide a constant fuel pressure through the remaining fills until the lift pump recycles again.fuel most likely is not able to flow through the filters quick enough to make up the deficiency even if the constant pressure is still available at the lift pump.

As I have said I feel this is a long term deficiency problem that wears the first cylinders rod bearing faster. Why I know something is going on is the engine sounds different with different fuel pressures to the base of the injection pump. The power balance of the engine sounds better with good pressure as well. . Anything you can actually hear has got to be signifigant.

Plus in corrected situations there seems a little more power available in the seat of your pants. With that relief valve closed because of not enough pressure to keep it open. The pulses that are generated inside the base of the injection pump are fierce. How and if they contribute to the issue is another unknown to me.

Now back to your oil viscosity issue.I am no rocket scientist. Say you have a car on 10-30. The car is burning a quart of base oil every 300 miles. You change to a straight 30 weight. Your consumption on average will drop to 5-600 per quart usually..

The only change that seems reasonable to me is the viscosity in effect must remain better. The multi grades state they protect to the same. Still it almost cannot be on a true overall viscosity basis.

The 10-30 has a polymer type component that changes with temperature. The molecule size of it might be much larger in any temperature state than oil. Or only at higher temperatures.

We all realise that a 240d on 15-40 will usually consume more oil than normal on the highway. I attribute this to the higher rpms on average it must run at in comparison to the 617 for a usable speed. I do wonder if the same engine was on straight 40 if the consumption pattern would be less or more on the highway. I suspect it might be less. Just not certain of that either.

Another thought along this line.If you are burning multi grade oil. Is the polymer being burnt up at the same rate? If not by continually adding oil you would have an increase overall of the polymer component. That may be good or bad. I just do not know.

The producers of the multigrade oils have not been particularily open about the whole picture. My wifes car for example takes a 0-20 synthetic oil. To keep the warrranty valid they want only certain oils used. This has led my to wondering why the synthetic oil must be special. Plus what is in it that is different than the normal run of synthetics.

The best yardstick I have been using to determine the probable life left in my engines is the oil consumption rate for a long time now.There is a serious problem with wear. Once it reaches a point it almost exponentially increases.

I would at least take off the lower oil pan, since fairly easy. One often must do that to replace a leaky gasket anyway. That might give enough view to tell what is wrong. As I recall, all you can see thru that hole is the oil pump, lower timing chain, and #1 cylinder, but perhaps a mirror would let you see all the rods. You can rotate the engine with the crank bolt, with exactly the right socket to fit the narrow gap to the fan shroud. The bolt on the p.s. pump is tempting. People say not to rotate the engine using it, but I have.

I agree that if the metal shards are from a bearing, then the crank is probably marred, but doesn't hurt to inspect if you can.

NOT PEOPLE...

The Mercedes Benz Factory Shop Manual specifically forbids using that nut to turn the engine.

That is a tapered shaft and pulley inside and you can ruin the shaft over torquing it... which by definition turning the engine will do. But it is YOUR car and you are free to mess it up as you please by not following what the factory says is correct procedure... they make these rules just to harass owners.. not because they know that much about the cars....

Not a dog with a bone syndrome. I am wide open to others thoughts. My thought is rather than differant amounts of element fuel fill and that is probably occuring. The principal suspicion is the sequential timing is changed as with any element getting less fuel than another.The injector will open later than another one. The effect being a timing reduction more likely than a fuel amount. Any element overloads in a good fuel pressure situation.

The lift pump is a constant pressure type but at the same time only recharges once per injection pump revolution. Filling the later elements in a a really low fuel pressure initial setup may mean they are almost scavaging from the decreasing low pressure profile available down the line of sequential loading.

Since the relief valve is no longer functional. There is nothing to provide a constant fuel pressure through the remaining fills until the lift pump recycles again.Fuel most likely is not able to flow through the filters quick enough to make up the deficiency even if the constant pressure is still available at the lift pump. Any filter acts as a restrictor to some extent.

As I have said I feel this is a long term deficiency problem that wears the first cylinders rod bearing faster. Why I know something is going on is the engine sounds different with different fuel pressures to the base of the injection pump. The power balance of the engine just sounds better with good pressure as well. . Anything you can actually hear has got to be signifigant.

Plus in corrected situations there seems a little more power available in the seat of your pants. With that relief valve closed because of not enough pressure to keep it open. The pulses that are generated inside the base of the injection pump are fierce. How and if they contribute to the issue is another unknown to me.

Now back to your oil viscosity issue.I am no rocket scientist. Say you have a car on 10-30. The car is burning a quart of base oil every 300 miles. You change to a straight 30 weight. Your consumption on average will drop to 5-600 per quart usually..

The only change that seems reasonable to me is the overall viscosity in effect must remain better. The multi grades state they protect to the same. Still it almost cannot be on a true overall viscosity basis.

The 10-30 has a polymer type component that changes with temperature. The molecule size of it might be much larger in any temperature state than oil. Or only at higher temperatures.

We all realise that a 240d on 15-40 will usually consume more oil than normal on the highway. I attribute this to the higher rpms on average it must run at in comparison to the 617 for a usable speed. I do wonder if the same engine was on straight 40 if the consumption pattern would be less or more on the highway. I suspect it might be less. Just not certain of that either.

Another thought along this line.If you are burning multi grade oil. Is the polymer being burnt up at the same rate? If not by continually adding oil you would have an increase overall of the polymer component. That may be good or bad. I just do not know.

The producers of the multigrade oils have not been particularily open about the whole picture. My wifes car for example takes a 0-20 synthetic oil. To keep the warrranty valid they want only certain oils used. This has led my to wondering why the synthetic oil must be special. Plus what is in it that is different than the normal run of synthetics.

The best yardstick I have been using to determine the probable life left in my engines is the oil consumption rate for a long time now.There is a serious problem with wear. Once it reaches a point it almost exponentially increases.

As for air cooled engines. I do not care if the manufacturere specifies 10-30. They are more prone to metal to metal contact. I only cut grass in warmer weather. So all our lawn tractors get straight 30 or 40 weight detergent oil.

We never have worn engine problems. The overall lawn tractors eventually all fall apart around engines that are still running as new. Although if the tractor had an internal 100 percent aluminium oil pump except the shaft. I might not do this.

My brother in law has said he has run into a few problems with modern oil pumps. The owners had been using a heavier oil than specified is what he thinks the issues may be.

wow thanks, a lot of good stuff on here.

i dont think im going to go down a fuel delivery pressure rabbit hole right now.


It ran about a min normally. I didnt prime anything. Just started it back up with the hood up to confirm/ deny wth was going on. No shake, nothing.

But it did sound like someone dropped a marble in it (exaggeration) prior to pulling over which is why I unquestionably pulled off.


I had changed the oil about 5 months ago.

I checked it and it was very low about 2 months ago. I added a gallon (and may have overfilled it at this point). The drip started shortly after: a slight drip from where the engine meets the transmission on the bottom seam.
Chasing the drip, I checked the oil and it was about two inches over. I drained a couple quarts to where it was about a half inch over.

I always use Delo 400 LE SAE 15W-40. I check the oil when its warm (not hot/ not cold).

Upon draining the oil to scope out the pan for shrapnel yesterday It drained about 2.75 gal. total.

__

Debating at this point whether to button her up and give it a shot. Or plan on pulling the upper pan this weekend with a buddy. I think Ill do both and just take a hit on 2 gals of oil but its raining now.:mad:

The evidence is looking otherwise...

first.... the setting of the fuel is done with the drip method ON THAT NUMBER one cylinder.... so if anything IT WILL BE CORRECT and the others 'overfueling' according to your visualization.

second.... even if that first one was getting less fuel no physics rule suggests that would cause more pressure on that piston... in fact it suggests less .

third.... the pop pressures are within a range ...none are perfect... and do effect the timing.. but there is NO evidence that what you suggest about number one.... and refer to ' first' ..... would cause it to be out of sync with the piston movement....

Two point Seventy Five ..... GALLONS .....?????
is that correct for what you drained out ??????
How much is your car supposed to hold ?

sorry, it was about 2.5 gal. total that came out, yes. (plus what I pulled the night before chasing the leak pre-problem)
it filled up a 2.5 gal Topsider Oil Extractor Can when drained to check the pan.

So it was about 2-3 qt over-filled still. is this a serious factor?

OK...
here is a potential reason for the failure..
Overfilling is WAY BAD because it can put the oil level so high that it is whipped by the crankshaft .. or the air around the crankshaft... so it oxidizes it......
that VERY QUICKLY takes away its lubrication properties..

So it sounds like you added a gallon when you thought it was low, two months ago, and it immediately began to drip oil from between engine and transmission, which may mean the oil level was overfilled by 1 gallon (4 qts) or more, and was lapping at the rear main crank seal, which is not designed to have fluid pressure against it and promptly began leaking.

leathermang's comment on the crankshaft whipping the oil is right on, all that splashing would add air bubbles into the oil, which could then get sucked up by the oil pump and from there reduce the lubricating and cooling ability of the oil, so then bearings may have suffered.

What is really curious to me is that you say it ran with no noise and smooth idle for a minute right before the tow. Maybe when you let it sit, the air came out of the oil, and there was enough oil pressure / lubrication to temporarily prevent the knocking?

OH... I did not visualize it past the oxidation... that is a very likely scenario....once you have significant actual bubbles in the oil then the oil pump immediately has pressure problems just the way a brake system with air in it does... the air compresses.... so your whole ability to push oil under sufficient pressure to those bearings is compromised FAST....
Good Catch....

I still think the OP should put it all back together and see how it runs. Depending on the quality of the oil and how long/hard it was driven, the engine may just survive. The metal in the pan looks bad, but the short idle time with no noise and smooth idle gives me hope.

If the engine sounds fine and runs fine, I'd drive it for a thousand miles or so with a fresh oil / filter change, and then send an oil sample for lab analysis and you'll have a very good idea of the internal condition of the engine.

And when you need to rotate the engine for valve adjustment , use the starter , either the jumper box under hood or have a friend turn the key on and off for you. Way easier

closed it up after valve adjustment, battery charge, new oil filter, 6 quarts Delo 400LE 15W-40.
The NSS is still down which failed a couple days before the tapping/ knocking.

https://www.youtube.com/embed/GsWpVpcLDk4

still appears to have a pronounced knock.

Have you used a stethoscope to locate the sound?


Also crack open each of the injector lines one at a time while running to see if the noise goes away on a dead cylinder. If it does, it might mean a bad wrist pin or rod bearing.


.

Probably a polarizing choice on here but planning to remove the upper oil pan with the engine in to get a good look at my new boat anchor. Best case would be bearing replacement.

Anyone have experience doing this? I do have the FSM document from charmalu's post.
What risks do I run?
Would removing the head be easier?
Correct sealant/ torque?

Thanks