1952 Cat D4 7U help spun rod bearing

KeithRa · May 28, 2013

I just bought a D4 7U that has a spun rod bearing. I was wondering if it could be done in frame or would motor will need to be removed. I got the head off and one side cover. I'm want to repair this little machine the under carriage is about 90%. Any help would be appreciated

NCWayne · May 28, 2013

If the journal on the crank is OK then there's no reason you can't replace the parts with the engine in the frame. If the journal is going to have to be ground to repair it, then by default they all will. In that case the engine will need to come out. While it's out, think about it, something caused the rod bearing to spin, be it low oil pressure, trash in the system causing a blockage to that bearing, etc, etc. Because your already having all of the rod journals ground your going to have new bearings in all of those spots, and while the crank is being ground why not have the mains checked too, and on, and on. Basically one part of the repair begs for the other, whch begs to go one step further to do it right, and on, and on. In other words you might as well plan to go ahead and do a full rebuild while you've got the engine out and torn down, just to be safe. Personally I've seen too many people decide to 'cheap out' and not do it and come to regret it later....

KeithRa · May 28, 2013

Thanks for the reply. I been trying to figure out this machine. The machine has no wear showing on pistons and liners or valve train. The only thing I seen funny was the thermostat laying next to the seat. This machine looks to be low hour machine. I was thinking he overheated machine or ran it low of oil on his hilly property. It's the forth piston rod back from front of engine I was thinking farthest from the oil pump. Thanks for your help.

Old Magnet · May 29, 2013

It is not necessary to pull the engine to remove the crank. Requires removal of auxilliary spring to engine nuts then jack up the engine to where there is sufficient clearance to drop and remove the oil pan over the equalizer spring.

NCWayne · May 29, 2013

I've never pulled one from one of the old D4's myself, so school me please. I can understand how you get the oil pan down by doing what your saying, but I can't see the crank coming out the bottom like that. I say that because most of the CAT's I've worked on you usually had to have at least part of the front cover off for the nose of the crank to clear on that end. Then, on the rear you had to have the TQ or clutch, flywheel, and often the flywheel housing, etc, etc, off for clearnace on that end.

Like I said I've not had one of old 4's down myself, but to me what your saying doesn't make sense based on my past experiences. Please explain so I'll know better next time. Thanks, Wayne.

Old Magnet · May 29, 2013

Well, your absolutely right, had it in my mind to access the bearings by pulling the pan. Still have to deal with the front timing cover and flywheel housing to remove the crankshaft so pulling the engine is required. Sorry I misled you.

NCWayne · May 30, 2013

Thanks for the answer. I'm the kind that learns all I can, so I tend to know a little about alot of things, ((and sometimes alot about a few things..LOL)) but I also know that there are alot of others out there that know alot more about alot of those same things than I do. That said I had a feeling that what you had in mind was accessing the bearings and basically doing an inframe, as that thought crossed my mind at first too, but your first answer had me questioning myself, so I had to ask.

jm. · Jun 1, 2013

Wayne : Now granted this was in the late 40s or early 50s but at that time local NAPA store had a man that would come to the FIELD and grind a crankshaft. Now I am not certain he could grind rod journals can,t see how that would work but my grandfather had a dozer go down and they did grind (Maybe only one journal) the shaft in the machine. I was like you on Olds post on removing the shaft from the bottom.

michael crowe · Jul 1, 2013

Sir, if you decide to part it out, I would be intersted in the undercarriage. Thanks. I need the rails and real sprockets. 816 898 7277

Randall Watts · Jul 22, 2013

I have a 49 cat 7U serial 7U 5382. I will part it out. the crankshaft is good. I installed a set of rings and rod bearings in it and got it running. It ran very well for a short time. Then a prechamber blew apart. I had to weld a long bolt to the bottom portion of the pre chamber that was still screwed into the cyl head. When I screwed it out a some of the threads in the head came with it. Installed a new prechamber and it blew bubbles in the radiator. So i parked it. that was 35 years ago. The rails pads and sprockets are good I estimate 75%. The cyl head is bad and the block has been frozen and cracked. I bought a 4&1/4 bore road grader engine for it. However I have come to the realization ill never get around to fixing it.

oldtanker · Jul 23, 2013

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1952 Cat D4 7U help spun rod bearing

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