'81 300SD rod bearings
 

Greetings from the rainless greater northwest.

I have posted before about the knock in this car. If I opened the feed to no.1 injector the knock went away. After trying the "purge" route with no improvement, I dropped the lower oil pan and removed the bearing from no.1 piston. The bearing was worn and I thought that the bearing was worn and looked wierd around the center oil groove. Then I looked at the pictures of new bearings on Fast Lane and and and they dont have an oil groove !!!!!! Are some sets with and some sets without this groove? Also I didn't note which way the rod cap was oriented on the rod, but when I match the wear markings on the two halves the indexing tabs are on the same side. I always thought they should be on opposite sides. Could it be that the person who put this together put the cap on wrong. According to the papers in the trunk it was overhauled about 50,000 mi. ago. So I only intend to replace the one bearing set. Any suggestions or words of advice out there? Also the hard rubber pick up with the screen was broken but the screen was still on the pump so nothing got into the pump. Thanks for listening to this long winded tant. Lee

If you don't have a factory shop manual you can do a search for ' skinnerbox' on this site... the engine manual is there....
It gives lots of good info including important warnings....

Thanks leathermang. I have been trying to get the skinnerbox site to work but it doesn't seem to want to cooperate. I have used it before, in fact just a couple weeks ago, but it doesnt seem to want to go to the Adobe acrobat reader function. Lee

" Also I didn't note which way the rod cap was oriented on the rod,"

That is one of the kinds of warnings they have in the engine manual... some of which are not found in the Haynes...

Can you tell by looking at the other rods which way the cap was positioned ?

Improvements and changes happen on bearings all the time.... you would need to check official sources and/or Tech Service Bulletins to find if the non groove ones are ok to use..

I have always liked grooves in bearings.

I'm almost certain that the cap and rod have a number stamped on the same mating side.

I want to see how this guy buys one rod bearing
 

I mean gee if you had the pan off and everything why wouldn't you replace all the rod bearings. I guess when you are retired you have the time to replace bearings one at a time....A lot of rod bearings don't have the oil groove.

"I'm almost certain that the cap and rod have a number stamped on the same mating side."---Pete Burton

As a large " whew , that was close" is heard escaping from Lee...

As to :
"...A lot of rod bearings don't have the oil groove."

Back when I cast my own babbit/nickel bearings I always cut a spiral groove in them... Then all of a sudden no one was driving buggies with horses...

Edit: convinced that accessing all the rod bearings probably not reasonably possible without removing engine.

It probably depends on the width of the bearing whether they put a groove in or not. Probably more important is the oil passages in the crank. Are MB diesel cranks crossdrilled?

The tabs on the rod and cap go together..same side..... there are no 'grooves' in a rod bearing, only in a main bearing upper. Cap tabs always go on same side as tab on rod or main cap to block. These are to 'orientate' the bearings and caps, the 'crush' is what holds the bearing insert in place.

If the wear face of the rod bearing has a groove, then it was worn there, not manufactured there.

The rubber nose on the oil pick up is to stop vibration from fracturing the oil pump pick up spout.( Anyway...this seems as good an explaination as any..) The screen needs looking at vewry vewry close..... as I had a screen with a gap that allowed a small peice of brass to jamb the pump, tear the oil pump chain apart and destroy the engine within 2 miles at 70 mph....on a customers engine!


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Remember that there is basically two oil pans on such an engine, the lower sump and the upper full length one. I believe Lee removed only the lower smaller pan which only allows you to access the first one or two rod ends.
I am not sure that you can get the main pan off without pulling the engine or ripping apart the front end (steering, cross members, etc). And if my memory serves me correctly, that cross member is what the motor mounts hook to. Does the upper pan bolt on from the top down on the outside or is it on the inside?
I've been emailing him and asked the same question myself...sadly all rods are not easy to get to at this stage.

A picture for the forums enjoyment :)

http://brandon.importtransmissionexc...icture 047.jpg

Brandon, thanks for clearly showing that. It's indeed true that the first rod can be accessed like that, not sure about #2, but the others, no way. The engine needs to come out. The lower pan is very accessible on this car, but the upper -ouch! All those M6 allen screws, the M8's buried in those deep recesses and the M12's from the bellhousing. Although you can get to all one way or another, it's less work to pull the whole powertrain, and less chance on stripping something.

A big thanks to all who responded. As Brandon put it "I only have the lower oil pan off so the other rods are not accessable". If I had the engine out I would naturally replace all of them, but with only a few thousand miles on the rebuilt it doesnt seem worth the while to do this. The groove in the bearing is too wide to be cast into it. I remarked that it looked wierd,and it probably was caused by something????? in the oiling hole in the crank. I will have to inspect that with a magnifying glass. There is not a lot of room in there. This job would be easier if the engine was out but that is not easy either. Also thanks, dkveuro, for that info on the bearing tabs. That is the way they were installed. I think the problem was foriegn material in the oil hole in the crank for no.1 rod bearing. The rod cap has one center punch mark on the cap so I expect that there will be a matching one on the rod.

Thanks again, Lee

Let us know how it goes back together.
I've found that pipe cleaners are usefull little tools when it comes to cleaning out crankshafts...guess ya just have to be careful not to push any foriegn crap upstream twoards the main bearings.
If you need any help, just drop an email. I live pretty close :)

After a lot of dilly dallying and a major event (my wife passed away) I finally got some things done on this engine. I replaced the rod bearing after using fine emery cloth (tape) to remove a burr on the journal, the bearing material came off with almost no effort. The journal looked very shiny and clean. Put it back together and had the same knock. (No.1) Got some advice from Brandon314159, and swapped no.1 and no. 2 injectors. Same noise but I noticed something that I hadn't before-when I cracked the fuel line to no. 1 injector the engine sped up, not a great deal but noticeably. It missed and shook a little more than normal but it did run faster. (probably 20 or 30 rpm). My first thoughts are that the timing for no. 1 is off but the rest are OK. I don't know how the injection pump works so I don't know if this is feasable. Does anyone have any words of wisdom? Luckily I have the "D" to drive while I mess with this one.


Lee

knocks
 

seems very unlikely that one can be off time and not the others. do you know how to distinguish bearing and or wrist pin noise? tap on deceleration is wrist pin, knock under accel is mains (i think) not sure what rod bearings sound like. someone will chime in im sure. good luck.