I thought my hydraulic woes were behind me (see original thread here: https://forums.yesterdaystractors.com/viewtopic.php?t=1380265 for details), but no. While I could lift some implements, the system clearly needed some adjustment to operate properly. I discovered yesterday that my draft control spring assembly was frozen solid from rust. The manual recommends this be disassembled every six months and the threads greased so that this won't happen but I would doubt mine's been done for several decades. I set out to get mine unstuck and following are some details that hopefully will help someone else out on down the road. Should serve as a cautionary tale of what's waiting if you don't do your maintenance, too.
The job starts with removing the top lift cover. It may seem like an intimidating job the first time around, but I can have it laying on the bench about fifteen minutes after picking up the first wrench if I hurry. Pull the seat, drain the hydraulic fluid, pull both side inspection covers, lay on top and reach in through both inspection ports to disconnect the control valve, unbolt the cover, and pull it off. Easy as pie and ice cream. The nuts holding my seat on require a 3/4" wrench (I doubt they are original) and all the other bolts should take an 11/16" wrench, unless any have been replaced with hardware store bolts, which will have a 5/8" head. Two of my inspection cover bolts are replacements like this.
Here's a scan from the parts book showing the TO20 draft control spring assembly. I've read the whole top cover is the same as the 2N/9N Ford, but have zero experience trying to swap parts between the two:
Trying to unscrew the hydraulic lift yoke as it sets is a fine recipe for disaster, as several of the parts it's attached to don't seem to be commercially available, or at least I've not had any luck finding them. The control plunger (p/n 10) will have to be supported in some way and while I found multiple references to the procedure, I could find not a single suggestion of how to go about doing it. I ended up going this route and can assure you, it's a solid setup. You'll see why I say that later.
Irwin 7" Vise-Grips, to be specific, seem to be a near perfect fit for this application. Back the retainer plate bolts out just far enough to allow insertion of the Vise-Grips and then snug the bolts back down to hold things in place.
Trying to hold the top cover while working on it strikes me as being a lot like wrestling a live octopus. It's unwieldy, heavy, there's something sticking off of it in every direction, nothing solid to get hold of, and so forth. I've never been able to generate much force at all with it just laying on a workbench and this idea suddenly occurred to me yesterday. Just might be crazy enough to work, right?
I think it would be much more solid with the drawbar stays in place, but I don't have a set. Still, it does provide enough support and rigidity to allow the application of some serious force and minimize all the flopping and rolling around that normally goes on.
In this position, I was able to fill the yoke cavity with penetrating oil (I used PB Blaster, which I've found to hold up well in high-temperature environments) and began the heating cycles on the hydraulic yoke. I've been soaking that cavity for several days. The cavity I'm referring to is where the yoke was originally drilled and tapped for the plunger. The drilled hole just broke out into the bore for the toggle pin, providing a port through which to spray the penetrating oil directly onto the rusted threads. I applied heat using a propane torch focused through gaps in the draft control spring and onto the shank of the lift yoke. The torch's tip was resting on the spring as I did this, my reasoning being that the torch's flame is relatively cool right at the base and would hopefully keep the spring from getting hot enough to affect its temper. It seemed to work because I could boil the PB Blaster up in the yoke while the spring retained most most of its paint.
I inserted a section of round bar stock through the yoke and slid a couple of pieces of pipe over it to make a large T-handle. A knee placed against one pipe and both hands pulling on the other will allow you to generate about all the force your body is capable of producing. Remember Bullwinkle trying to pull a rabbit out of a hat? "I guess I don't know my own strength!"
I'm not happy about it, but can move forward from here. The available replacement parts are on order from YT. Now for some random thoughts and observations, in no particular order...
There doesn't appear to be any way to get the spring control fork (p/n 31) out of the top cover without unbolting the hydraulic lift cylinder (p/n 10). The geometry is just not there. This matters if your fork to plunger pin and cotter (p/n's 33 and 36) are all rust-welded in place like mine were. I ended up breaking the cotter off on both sides and inserting a small file through the large hole at the back of the top cover to file down the remaining metal. Pin 33 is like glass hard, so you can feel when you've filed away any remaining cotter. The file will just sing as it slides effortlessly over the pin. Here's a scan of that page:
To drive out the pin, I supported the back side of the spring control fork with a 3/8" bolt, roughly 2" long, inserted between the tab holding the pin and the side wall of the top cover. This seemed to do a pretty good job.
You can't get directly to the pin to drive it out, so force has to be applied at an angle. For those unfamiliar with how this is done, you can use some type of drive pin with a spherical end. A typical square-ended punch would make an absolute mess of this job, but the spherical end will transfer force along a linear axis radiating from its point of contact, in effect allowing you to apply force "around a corner" to the stuck pin. The technique worked great to get the pin moving and I finished the job with a screwdriver tapping against the underside of the head.
I'll be coating the new threads with copper based anti-seize instead of grease. This is an extreme duty formula I've seen used on injection molds operating at over 400*F, so I think it will hold up here. If that doesn't work, my next plunger and yoke will probably be machined out of 304 stainless steel, and we'll see how that performs...
The job starts with removing the top lift cover. It may seem like an intimidating job the first time around, but I can have it laying on the bench about fifteen minutes after picking up the first wrench if I hurry. Pull the seat, drain the hydraulic fluid, pull both side inspection covers, lay on top and reach in through both inspection ports to disconnect the control valve, unbolt the cover, and pull it off. Easy as pie and ice cream. The nuts holding my seat on require a 3/4" wrench (I doubt they are original) and all the other bolts should take an 11/16" wrench, unless any have been replaced with hardware store bolts, which will have a 5/8" head. Two of my inspection cover bolts are replacements like this.
Here's a scan from the parts book showing the TO20 draft control spring assembly. I've read the whole top cover is the same as the 2N/9N Ford, but have zero experience trying to swap parts between the two:
Trying to unscrew the hydraulic lift yoke as it sets is a fine recipe for disaster, as several of the parts it's attached to don't seem to be commercially available, or at least I've not had any luck finding them. The control plunger (p/n 10) will have to be supported in some way and while I found multiple references to the procedure, I could find not a single suggestion of how to go about doing it. I ended up going this route and can assure you, it's a solid setup. You'll see why I say that later.
Irwin 7" Vise-Grips, to be specific, seem to be a near perfect fit for this application. Back the retainer plate bolts out just far enough to allow insertion of the Vise-Grips and then snug the bolts back down to hold things in place.
Trying to hold the top cover while working on it strikes me as being a lot like wrestling a live octopus. It's unwieldy, heavy, there's something sticking off of it in every direction, nothing solid to get hold of, and so forth. I've never been able to generate much force at all with it just laying on a workbench and this idea suddenly occurred to me yesterday. Just might be crazy enough to work, right?
I think it would be much more solid with the drawbar stays in place, but I don't have a set. Still, it does provide enough support and rigidity to allow the application of some serious force and minimize all the flopping and rolling around that normally goes on.
In this position, I was able to fill the yoke cavity with penetrating oil (I used PB Blaster, which I've found to hold up well in high-temperature environments) and began the heating cycles on the hydraulic yoke. I've been soaking that cavity for several days. The cavity I'm referring to is where the yoke was originally drilled and tapped for the plunger. The drilled hole just broke out into the bore for the toggle pin, providing a port through which to spray the penetrating oil directly onto the rusted threads. I applied heat using a propane torch focused through gaps in the draft control spring and onto the shank of the lift yoke. The torch's tip was resting on the spring as I did this, my reasoning being that the torch's flame is relatively cool right at the base and would hopefully keep the spring from getting hot enough to affect its temper. It seemed to work because I could boil the PB Blaster up in the yoke while the spring retained most most of its paint.
I inserted a section of round bar stock through the yoke and slid a couple of pieces of pipe over it to make a large T-handle. A knee placed against one pipe and both hands pulling on the other will allow you to generate about all the force your body is capable of producing. Remember Bullwinkle trying to pull a rabbit out of a hat? "I guess I don't know my own strength!"
I'm not happy about it, but can move forward from here. The available replacement parts are on order from YT. Now for some random thoughts and observations, in no particular order...
There doesn't appear to be any way to get the spring control fork (p/n 31) out of the top cover without unbolting the hydraulic lift cylinder (p/n 10). The geometry is just not there. This matters if your fork to plunger pin and cotter (p/n's 33 and 36) are all rust-welded in place like mine were. I ended up breaking the cotter off on both sides and inserting a small file through the large hole at the back of the top cover to file down the remaining metal. Pin 33 is like glass hard, so you can feel when you've filed away any remaining cotter. The file will just sing as it slides effortlessly over the pin. Here's a scan of that page:
To drive out the pin, I supported the back side of the spring control fork with a 3/8" bolt, roughly 2" long, inserted between the tab holding the pin and the side wall of the top cover. This seemed to do a pretty good job.
You can't get directly to the pin to drive it out, so force has to be applied at an angle. For those unfamiliar with how this is done, you can use some type of drive pin with a spherical end. A typical square-ended punch would make an absolute mess of this job, but the spherical end will transfer force along a linear axis radiating from its point of contact, in effect allowing you to apply force "around a corner" to the stuck pin. The technique worked great to get the pin moving and I finished the job with a screwdriver tapping against the underside of the head.
I'll be coating the new threads with copper based anti-seize instead of grease. This is an extreme duty formula I've seen used on injection molds operating at over 400*F, so I think it will hold up here. If that doesn't work, my next plunger and yoke will probably be machined out of 304 stainless steel, and we'll see how that performs...
