Old Magnet you may remember me with a previous discussion about running my D7-17A with diesel that had leaked into the crankcase. Well this past weekend I removed the bearing cap on #4 piston rod and it is in pretty rough shape. Trying to determine if I want to attempt to rebuild this engine. I know it will be a major project because of the shear weight of the engine around 6,000 pounds. The serial number is 17A16035. Would also like comments from anyone else.

Doesn't look good but I've seen worse and still operating. Question is what do the other bearings look like. Is there any noticeable knock coming from the engine and what do you have for oil pressure?

haven't tried to start the engine as I imagine all of the other bearings and mains look the same. The crank seem to take a lot of force to move it when I was getting it into position to remove the rod bolt nuts. The crank looked smooth when I ran my finger over it. I did not try to remove the top part of the rod bearing but I imagine it looked as bad or worse. Trying to decide if I want to tackle this big job. I need to find someone close to me that has had experience with rebuilding one of these engines. It is a shame this happen to this cat as it has been a good machine and has seen a lot of work. I am sure if it is rebuilt that it would make a good tractor for many more years of work.

Well, if the other bearings don look any worse than you could replace all the rod and mains and try from there. Cam bearings should not be that bad because the turn at a much slower speed.

Agreed, remove and inspect the bearings and journals. Might just get away with replacement bearings.

I am guessing the cylinders and pistons will also be rough as the diesel in the oil probably caused a lack of lubrication. When I noticed the oil pressure falling the water temperature was going up fairly rapidly. When I drained the oil and diesel out of the crankcase there was a lot of shiny metal flakes floating on the oil. I guess that was bearing Babbitt and maybe flakes from pistons and cylinders. Have not taken the heads off yet to look at the cylinders. I am trying to decide if I want to rebuild the engine out of the machine or just scrap the whole tractor out.

i agree. roll some new bearings in and proceed. i would feel the rod journals real good to make sure no metal is stuck to them.

What are the thoughts on cylinders and pistons? Do y'all think that there maybe some scoring of the cylinder walls and piston skirts?

How difficult will it be rolling in new bearings with the oil pan removed? I have not looked for where the diesel got into the crankcase. I am guessing it might have gotten in thru the fuel transfer pump.

Usual mystery source for fuel leakage that gets into main sump is the fuel gallery "O" ring seal between the fuel injection pump and the base of the filter housing. Leakage from the transfer pump would normally show up in the tell tale drain line coming from the transfer pump seal cavity.

Those old engines are pretty forgiving, I'd think you'd have to run until pistons seized in the bores before they would see significant damage.

Rolling bearings out and in is a bit of a job but certainly can be done. If your not up to the task better hire someone to do the job.