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SteveH
09-03-2008, 10:38 AM
Non-Toyota....but chime in if you can!

My '58 Massey 50 (Continental Z134 4 cyl gas engine) suffers from low oil pressure when hot and faint rod knock. I pulled the oil pan (cast iron!) and found the rod bearings on the inner two cylinders are toast. One pair is scuffed badly, and the other bearing shells have lightly spun in the rod. The crank is scored, but not horribly so. The outer two rod bearings look good and spec out with plastigage. I pulled the center main bearing (there are 3 mains) and it looks great.

Here's my question: The center main bearing oil galley feeds oil to the center two rod bearings, according to the I&T manual. How can the rod bearings be fried (presumably due to lack of oil) when the center main looks great and has been apparently getting oil?

I plan to blow compressed air through the oil galleys and/or insert pressurized oil through the oil pump relief valve to see if I can get oil flow through these passages. I'm trying to find the root cause of this oil starvation.

Worst case, I will replace the inner rod bearings with std. size or .002 over (a special tractor bearing for worn engines) and plastigage them and slap it back together. I won't pull the crank and have it turned, as this would require breaking the tractor in half.

Thanks for any ideas/observations!

Steve

Uncle Ben
09-03-2008, 10:51 AM
The main causes for journal bearing loss is dirty oil or oil starvation. Your low oil pressure at operating temp is characteristic of worn journal bearings which is what you found. How dirty was the oil? I would mic the journals and caps and see if simply slipping in new bearing half is enough. The hard part when clamshells spin is the babot finds places to hide in the oiling system and will haunt you later by eating the rear main seal or chewing up your new bearing half's. If you do slip in new clamshells be sure to buff the scored journals very well with crocus cloth. If not, you will be doing this again very soon.

SteveH
09-03-2008, 12:17 PM
UncleBen - thanks! Some of the babbit material is handily in the oil pan. Thanks for the crocus cloth suggestion - that's a key step, and one I had overlooked. This engine has a dual rear main seal - it has packing within the rear main bearing itself, and then a traditional lip seal on the output shaft. Both leak slightly, I suspect, but the leak is far from the clutch face.

Fortunately, the bearing didn't spin so much that it spit out a shell or tore up the rod end or bearing cap - they look fine, and are cast iron, so they're tougher than aluminum in any case.

I have always run straight 30wt in this tractor, and have changed it at least once/year. The PO may not have been nearly as careful on oil changes. I only put 10? hours a year on this machine.

leiniesred
09-03-2008, 01:39 PM
Hmm, We use (abuse?) a 1934 CAT Model 22 (stem-winder) up in Michigan. I think the oil was last changed about 5 years ago.

Isn't that continental the tall skinny one that I always see with the welded up crank case?

I love the classic farm gear. Crocus cloth and a hammer fix most everything. I say pull the bearing caps out, cut off a chunk of your leather belt, wrap it 'round the crankshaft, bolt the caps back on, switch to 50wt and run it. (keep the revs down though, eh?) :)

$200 new crank for you:
http://www.tractorshed.com/contents/adpic2860.htm

SteveH
09-05-2008, 09:54 AM
Thanks for the crank lead - that's half the price I've seen elsewhere. I suppose this engine is 'tall and skinny', but I've seen taller and skinnier. Seems like everyone has a diesel except me, but at least I have the 'high altitude' model that has some compression, unlike the standard engines. Since this maxes at 2000 rpm, 'keeping the revs' down isn't terribly hard ;-)

SteveH
09-19-2008, 10:04 AM
Semi-final chapter: I replaced the trashed rod bearings and cleaned up the crank with crocus cloth and put it back together. Same oil pressure. The crank had been turned .010 and the non-spun bearing was dated 11/76. So, this engine only made it 18 years before the first rebuild!

So, I pulled the pan and removed the oil pump. It was somewhat worn internally, so I ordered and installed a rebuild kit. The relief valve was stuck in its bore on the oil pump, and while I thought it was stuck in the closed position, it was apparently stuck partly open (read on...).

I un-stuck the oil relief piston, cleaned the bore, replaced all the parts including the piston, filled the pump with assembly grease, and reinstalled it. New pan gasket and yet-another 5.5 qts. of 30wt. Fired it up and - whoa - 60 psi of oil pressure! I ran the tractor for 10 min and it never dropped below 50 even at idle.

This morning, I graded the road and driveway and got it nearly full-hot - it takes some hard work to get this tractor to 160 degrees F.

Now, at 500 rpm (lowest idle) it reads over 40. It used to read barely 5 psi. The engine sounds quieter (obviously due to the new bearings) and runs well.

So, for now, I'm going to use/flog it and see how the oil pressure holds up. Word to the wise: don't let crummy oil pressure readings go untreated for very long! This tractor only survived this oil-pressure abuse due to its 2200 rpm max governed speed and giant-sized bearings.


Steve