[Farmall] O-12 Progress

[Karl Olmstead]

Got the '36 O-12 running again on Saturday. Finished machining the oil 
filter mount a couple weeks ago and bolted it in place. It's working well; 
almost no seepage around the filter cannister. The original mount is 
probably unusable; it's deformed and cracked from being tightened too much 
too many times. I used a tap screwed into the filter mount center hole as a 
guide to position the filter mount on my milling machine, then filled the 
old gasket groove with JB Weld, let it cure, and used a boring head with a 
1/8" cutter to cut a new gasket groove perpendicular to the center mount 
hole. This technique works very well, but some filter mounts are too warped 
and cracked to fix. I think that IHC realized that the oil filter mount had 
problems; they made three or four different models. One of the earliest 
changes was to add bracing to the underside of the filter mount.

Filled the engine up with diesel fuel, pulled the sparkplugs and towed the 
tractor around in gear for fifteen minutes. It failed the good ring test; 
lots of diesel fuel blew out of the spark plug holes. Worn piston rings. 
Surprisingly, though, the tractor doesn't smoke visibly.

Dropped the oil pan, which was a major chore. As expected, you have to 
almost remove the front axle. The alignment yoke that holds front axle 
straight needs to be dropped six or eight inches, which means that I had to 
remove the cap that holds the ball under the clutch and then drive out the 
front axle pivot pin, then lift tractor up until axle and alignment yoke 
dropped down away from the oil pan. I also removed the tie rod to get it out 
of the way.

There was a lot less sludge in the oil pan than I expected. I pulled the oil 
pump and cleaned up its inlet screen, which wasn't in bad shape. This 
tractor had clearly been maintained pretty well for most of its career. 
Cleaned up the oil pan and installed new gaskets, which is a pain on the 
F-12 family. Four separate pieces. It's all worse on the O-12 because it's 
down low and surrounded by the cast iron chassis. I'm not used to having to 
use jackstands in order to get to a tractor oil pan, and I don't like it!

Since I had so much of the front end dismantled, I cleaned up the tie rod 
ends and the axle pin holes and installed new grease fittings in everything. 
Future service will be a breeze.

Put everything back together and decided to wait on fixing the radiator 
leak; I wanted to get the tractor running. Filled the radiator with water. 
Cleaned and refilled the air filter. Installed a clean rocker arm cover and 
decided to wait on valve adjustment. Cleaned the sparkplugs and reinstalled 
them. Actually I forgot to put them in, and was puzzled when the engine spun 
three or four full revolutions for every pull on the hand crank. Oops.

Started the tractor and the smoke boiled off of the muffler and exhaust 
manifold. All that diesel fuel burning off. The tractor's a good runner, but 
seems down on power. Yesterday I tried to use it to pull a drag around the 
yard and out onto our access road, but the drag loaded up with wet sand (it 
had rained), and the O-12 couldn't maintain RPMs in second gear. Dropped to 
first, and the rear wheels just spun. Broke out the '36 F-20 and finished 
the job with it. I have pulled the drag with my F-14, but it has a fresh 
rebuild and 3.25" high compression pistons in it. Big difference!

The transaxle on the O-12 is still full of mucky old transmission oil cut 
with diesel fuel; I need to run the tractor some more and drain that mess 
out. The tractor rolls noticeably easier now; the lube was so thick that I 
couldn't even push the little tractor by hand. I'm not looking forward to 
draining it. Nor replacing the radiator core. But it'll happen eventually.

-Karl