300SDL Tap tap tap to clank clank clank!
 

I would like to start out this new thread thanking all those who helped me so far with my jammed oil pump problem.

I had the engine running fine -new pump, rod bearings, etc. -and decided to change out my motor mounts before I put the vehicle back into service. Very soon after starting the engine with the new mounts, I started hearing a single cylindar tap tap tap, especially above idle. It has now grown to a loud clank clank clank, along with a scary rubbing squeek. I have oil pressure -3 bar above idle. This new noise is really loud, and sounds more like a hammer against the side of a cast iron bathtub than one driving a nail.

It sounds really bad -is it all over for this engine?

Ok -I've gone out and tried firing it up a couple times since my last post. The clanking is now a full on banging and squeaking. I still have great oil pressure. Like I said, it was running great before I changed out the motor mounts.

Oddly too -the "stop" lever was all the way down while the engine was running, and when I was checking around on that side -engine off -I bumped one of those plastic vacuum lines and it disconnected, and the "stop" lever popped up to where it normally is -does this make any sense? I don't know much about those lines -just enough to re-connect them when they get disconnected.

post a video if you can... but if there's banging and squeaking I would NOT run the engine...

First off do you know that when the oil pressure gauge fails it reads 3bar?
Could the banging be the vacuum pump?

I think it's too loud to be the vacuum pump

You did do a plastic gauge on the existing main bearings and replacement rod bearings.

The squeeking is ominious. I would want to inspect all the rod bolts if you did the plastigauge check.

If really solid, especially if you hear it cranking, sounds like a spun bearing. And yes, verify that the oil pressure sender is accurate, shouln't run 3bar always as that indicates open circuit IIRC. If not that solid, maybe the vacuum-pump has failed and not yet terminated the engine?

Where are you located? I have the short-block out of my '87 under my workbench.

I went out this morning and cranked the engine without waiting for the glow plugs. There was no clunking or squeaking -it sounded like a normal engine cranking. Once it fired though, the clunking started again.

It has the new model vacuum pump installed.

My 86 did the same thing. A loud tapping similar to a hammer hitting the block.

It was easy to diagnose on mine though..........
at 70 mph it turned itself into a 5 cylinder!!!

Rod came out both sides of the block and a big chunk of metal came out the oil pan.

4000lbs of Mercedes was airborne for a few seconds. :eek:

Pull your pan and check your rod bearings sounds like ones about to come
apart.
Maybe a loose or broken rod bolt?

Maybe a lifter collapsed ?
That's what I was told my noise was.

Regarding oil pressure questions, begining from initial firing the gauge shows a build from 1 bar to 3 bar within a few seconds. From what I hear, a faulty gauge goes directly to 3 bar -is that right?

Since this engine is in the process of being cleaned out after it's melted rod bearings were replaced (it's been run perhaps a total of a half hour since the replacement), there are many small babbett particles in the pan oil. Could it be that there were enough particles to clog the filter and starve the top end, causing some lifters to flatten, with the result being this irregular firing and banging and perhaps the squeaking too?

Unfortunatly collapsed lifters do not squeek. The babitt on his rod bearings had melted. I was originally concerned about the state of the main bearings although his description sounds more like a rod bearing at this point.

I just hope he at least plastigauged the main bearings as well as the replacement rod bearings. The rod ends should have not distorted as he never spun a rod bearing. Unless they got very hot . We know they were pretty warm.

It does sound like the cheapest and most reliable course of action is something like the short block a member is offering. Do not totally discount the vaccum pump as it was without oil on the ramps for quite awhile perhaps. Not a likely senario but the engine can be fired with it off for a short time. You would save it from the old block anyways so it is not really additional work.

Sometimes in life things go our way and other times not. We do not like to be on the recieving end when they do not but someone has to be there.

I tried pushing the low oil pressure warning device application to all these older diesel engines as a lesser evil. My personal feelings have not changed since.

It unfortunatly takes events like this to show the advisability of incorporating one. I also hope I am wrong as it gives me no satisfaction to see a member going through an event like this.

Even if the oil filter plugged up with babitt particles it would go into the bypass mode I believe.

Dosen't the pump bypass simply empty back into the pan? in which case couldn't a clogged filter end up starving the top end -and everything else? If there is another bypass, sounds like my problem would be lifters full of babbett. The reason I came up with the clogged filter idea is because at one point, I checked the oil level and found it to be almost nonexistant on the stick -so I checked the oil filter housing and found it so full that a fair amount came out upon opening the lid. I let it sit awhile for the level to go down and then replaced the filter with a new one.

Since I mic-ed each rod journal across multiple quadrants to find any damage and determine which bearing sizes to order, I saw plasticgauging as redundant, as it would require my using -and possibly damaging -the new bearings anyway, as the old bearings were mostly melted and totally unusable for plasticgauging. Also -we are talking about my running the engine for at most a total of half an hour since bearing replacement -I sincerely doubt any variance found between plasticgauge results and multiple millimeter caliper readings -to the third decimal place -would be the cause of the severe noises I am now experiencing.

I believe that the bypass valve simply bypasses the filter allowing unfiltered oil to lubricate the engine. The bypass valve is there to prevent oil starvation in the event of inadequate flow through the filter.