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Crank main and rod bearing help!

M

Massey_165

Member
Hey guys, I am working on a Massey Ferguson 165 Perkins diesel, I was loosing oil pressure when hot. I have the motor out and have measured the crank main and rod bearings, the main bearings are in spec, the rod bearings arent and I found one rod bearing scored pretty bad so Ill replace those. Should I replace the main bearings also? I am doing this in frame so it would be easier to not do them but will if I should.
 
you said motor out then you said in frame. Which are you doing? Actually, it is not a motor. it is an engine.
 
I would start with measuring the rod journals and evaluating the scoring. If out of tolerance, or rough, that answers the question, it will have to come out and be ground. Usually when a bearing fails it has a reason, something wrong to cause it, and now even more damage was done in the process.

Doing in frame has it's disadvantages. Dirt is a major one, the shed material off the bearing went somewhere, and it's still in there! Can't measure the main journals. Can't replace the rear seal (most designs).

Diesels are very unforgiving. My vote is take it all the way apart, assume nothing, don't give Murphy a foot hold!
 
I have the engine on a engine stand upside down, not in frame. I wasnt going to fully remove the crank if I could get away with it. This is all new to me, just doing it and learning as I go. I used plastigauge and the main bearings were .003, the rods bearings .002. The first rod bearing was scored but the crank was smooth.
 
I used plastigauge to measure them, I didnt see any scoring on the crank, just the bearing but I also didnt look and the other half of the crank journal.
 
I have the engine on an engine stand upside down, not actually in frame, but was hoping to not have to pull the crank out. The crank didnt look scored just the bearing, but I only observed one side of the crank journal.
 
If the bearing is scored I find it hard to believe the journal is in spec. Whatever caused the rod bearing to be scored went through the main also. If as you said the engine is out it's not much more to remove the crankshaft, your going to buy bearings anyway so if the crank needs reground it would not be that much more expensive at this point.
Why take the chance?
 
Just to add to the comments. If it is accessible might just as well take the crank out and have a machine shop go over it and size your bearings.
Just to add to that if it is one journal on the crank and you get it early enough miracles can happen with a strip of fine
emory cloth. I did a journal in place on a Ford 302 that began to tap. Took a few hours with emory cloth, put together with one new bering and lasted for 150,00 miles before I traded it. My friend did the same ( I helped him)with a Cockshutt 30. Took two weeks after work, 15 or twenty minutes a day to polish down a high spot, miked bearing and put in new one. Tractor ran well after. Lucky stiff, he paid 50.00 for tractor
and 20 for the repairs.
Kris
 
You need to send the crank and rods to be checked and turned or polished if they need to be . Send it to decent shop not like the one I sent my block to
 
When you say the rod bearing looked scored, but there was no damage to the crank. Is it possible that some trash got the rod bearing and didn't mark the crank? Or maybe the rod bearing overlay fatigued and a piece popped out and that is damage to the bearing? You will have to closely visually inspect the crank, with a good light and eyes to be certain there is no crank damage.

If there is no discernible damage to the crank on any of the bearing surfaces, I would be OK not pulling the crank and installing all new bearings (rods and mains).
 
you left out the most important detail,... camshaft bushings. is the first thing when oil pressure drops hot.
 
pretty hard to give an answer when no clearance's are given. not even the type of oil being used. no oil pressures to go by, if mains look good leave them alone, that is not the problem. you dont have to pull an engine to check clearances. at least post a pic of the scored brg. confusing here,... you are doing this in frame but u have the engine out???
 
was thinking that , but not much info here to go by. those clearances he posted i just saw are not all that bad but getting on the loose end. i dont think its enough for the pump not to keep up. think he better look into the oil pump first. like why pull an engine out.? plus give some oil pressure readings.
 
No. The block probably does wear some. But if it is really worn enough to lose oil pressure at the cam, the engine probably isn't worth fixing as it would require a new block.

The crank usually wears out first. On most four cycle engines the crank turns twice as fast as the camshaft.

Like the other guys said, he really needs to take the crank out and get it measured with micrometers. There probably is just too much clearance between the crank and bearings, especially the rod bearings. And there is a difference between looks good and good tight oil clearance too.
 
I replaced rod bearings on my last in frame project. Didn't have any problems. BUT, the old bearings were just normal wear, nothing scored. Was gonna replace the mains to, but ended up getting new ones that weren't the right ones. Oh, well. After looking at the old ones, they surprisingly showed very little wear if any at all. I plasti-guaged em one at a time. They plast-guaged out within spec. So just re-used the old mains. Maybe not the right way to do things. But that's what I did.
But I will say this. I've got some internal engine experience under my belt. I do know what I'm looking at, what will fly, what won't, what you can get away with, ect. I wouldn't advise someone to be making partial overhaul decisions without any experience under thier belt.
When plasti-guaging main bearings with crank and block in frame, you better know what your doing. Well, if you don't, you'll come up with in-accurate and or un-tolerable readings from doing it wrong.
 
The main bearings were .003 and the rod bearings .002, Ill try to get good pictures tomorrow, one rod bearing was scored but the crank journal felt smooth. I worked the tractor over the summer, after warm and running high rpms the oil pressure was fine, but when I would let it idle the oil pressure would drop to zero. I didnt mean in frame, I have the engine out and flipped on an engine stand.
 
I'm assuming you mic'ed the crank. If not, you should. Journal diameter, journal taper and journal out-of-round all need to be in spec. I would not make a decision on replacing anything until I had a clear picture of the crankshaft condition through measuring. Pressure is equal and undiminished in all directions, so anywhere in the pressure system is suspect until proven within spec.
 
(quoted from post at 19:19:09 01/27/22) pretty hard to give an answer when no clearance's are given. not even the type of oil being used. no oil pressures to go by, if mains look good leave them alone, that is not the problem. you dont have to pull an engine to check clearances. at least post a pic of the scored brg. confusing here,... you are doing this in frame but u have the engine out???
Click to expand...


rustred, if you were to read all of the info that has been posted you may not be confused.
 
It's your engine and your money and your time, but if I had gone to the point of putting it on an engine stand I would completely rebuild it like it should be. A Perkins diesel is one of the cheapest engines there is to rebuild. We rebuild engines almost every day and you get what you pay for. Put a new or reman oil pump in it too.
 
From what we have heard so far I think your oil pressure problem may be from something other than the main and rod bearings ?
 
i read what the poster posted, yes it confused me, didn't it make u wonder also? it made others wonder also. plus his first engine job so he
better get an overhaul manual to follow which will include the spec's. lots of info here just some is a lot more costly for the end result.
the crank should be measured in the block before removal , not after. separates the hands on mechanic's that know what will work and what
wont work. i highly dont believe he will be sinking more money in the engine than the tractor is worth. this engine is in a stand sitting
taken apart when actually there is good possibility it did not have to get this far. but if money is not the problem then yes go for it take
it all apart and start from scratch.
 
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