8N hydraulic troubleshoot

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Posted by Travis on March 04, 2019 at 13:40:23 [URL] [DELETE] :

I used the winter to completely tear down, clean, inspect, and rebuild 100% of my 1947 8N hydraulic system. Added the NAA piston, replaced the relief valve, rotated the cam follower pin 180 degrees (it was worn about 20% of the way through). Adjusted with jig, and made sure everything was straight and torqued to spec. Topped off with TSC Renew 134 hydraulic/transmission fluid.

Weather here is amazing now, days reaching 50 degrees and soil draining well.

Decided to unload a heavy disc off a trailer using a pole boom, rigged about 3/4 of the way out. Yes, this was very heavy and I was using it as a test for the hydraulics and bleed down.

After loading the disc and lifting it, the lift wouldn't go down! The tractor became a stunt tractor and wheelied no problem. With two men on the hood we lowered the tractor and moved forward 10'. Slowly unloaded the humans and let the disc sit on the ground, front wheels in the air.

Then, I let her sit over night to see if the hydraulics would bleed off and they didn't. So, good news, for the cylinder and piston, there. Then, I used a come-a-long to remove the chains from the boom and the disc, lowered the tractor down a few cogs at a time, no problem.

Fired the tractor up and I could raise and lower the boom, unloaded, no problem.

Mounted the disc to the three-point and I can raise and lower it, no problem.

Mounted the boom back on, lifted a two bottom plow off the trailer, and again couldn't get the lift to drop down.

Appears that with a very heavy load I can't get the lift to drop on demand. With lesser load I can.

Also...

The draft / position control level is a bit weird. When the lever is in the vertical "up" position the lift works quite well. When it is the horizontal "down" position the lift works very slow unless I push the end of the lever down manually about 1/16" further than were it naturally wants to rest. When I do this, the lift responds very quickly and raises in about 2.5 seconds. Not sure what I happened there either, or if these things are related.


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