L785 servo problems

[PADeutzguy]

We unloaded this machine 7-3-1993 brand new. It's now got nearly 7,000 hours (construction, farm use) on it. Mostly only my father and brother and I use it, so it's decently well kept machine, but has been neglected to a degree. For the second time the right drive servo (steering) blew oil out the back. Looking at the online parts book, there shouldn't be a hole behind the lower spool leading out to the double rubber/steel bushings, yet I have a hole back there oil is just dumping out of. This happened to my brother about a month ago and he said he just put the "cap and O ring" back in place. I'm not seeing how that was possible, that was only a hole back there today. It worked about 5 hours since he "fixed it". When I say it was neglected, it was allowed to run for years with those rubber/steel lined bushings worn completely through. I'm thinking this is how the hole was made in there? I didn't get to look closely at it, but it doesn't look worn through, but I'm not sure what else could have happened to it? I just took it off, put it in the bed of the truck and went home disgusted. Thoughts? Comments? Where to get a good used one? New Holland wants $1300 for it, yea right!! Randy

 

[mfyock]

Used ones are pretty hard to find.I bought an L785 with a missing servo a couple years ago. Spent hours calling around, and finally found one. Since then I bought a brand new servo off a dealers shelf. Never used. I would part with it for 50% new price. Its a lot of money, I know, but I can always keep it for a spare....

 

[PADeutzguy]

Used ones are pretty hard to find.I bought an L785 with a missing servo a couple years ago. Spent hours calling around, and finally found one. Since then I bought a brand new servo off a dealers shelf. Never used. I would part with it for 50% new price. Its a lot of money, I know, but I can always keep it for a spare....

Send me your contact info, as I'm new here, I don't know where to get yours. Let me talk to the machine shop about boring it out and putting a brass sleeve in it, and see if that will seal it. I see the disk/plate is in the bore now, but what holds it in there? Wonder if it can be welded in?

 

[Mike10]

It sounds like your brother and you have had different problems. What I don't understand is why oil is coming out around the rubber bushing. The steel outer sleeve of this rubber bushing should be a press fit in the servo housing. If the bushing falls into the housing then either the bushing is wrong or as you stated the housing is worn. As tight as the bushing is supposed to fit in the housing I would think you would not have much of a leak if any even with a hole in the housing.

 

[PADeutzguy]

It sounds like your brother and you have had different problems. What I don't understand is why oil is coming out around the rubber bushing. The steel outer sleeve of this rubber bushing should be a press fit in the servo housing. If the bushing falls into the housing then either the bushing is wrong or as you stated the housing is worn. As tight as the bushing is supposed to fit in the housing I would think you would not have much of a leak if any even with a hole in the housing.

I'm sure they are the correct bushings, I rebuilt them all in 2011, and at $25 each that wasn't cheap. I think they fell out in my hand, or I may have had to use a punch to remove them, but these ones (the new set from 2011) slide in and out by hand. They are very oil soaked obviously. But I doubt that's what New Holland intended to keep the oil in, as there are 2 bushings in there, side by side, so oil would come out between them even when it was new under operating pressures. Does that cover plate go "outside" the bore and held in with the bushings? May be it's so worn it's falling into the bore? The online parts book shows nothing and the service book doesn't mention it either. I'm concerned even a new sleeve won't cure it, as it will leak around that too.

 

[Mike10]

I'm sure they are the correct bushings, I rebuilt them all in 2011, and at $25 each that wasn't cheap. I think they fell out in my hand, or I may have had to use a punch to remove them, but these ones (the new set from 2011) slide in and out by hand. They are very oil soaked obviously. But I doubt that's what New Holland intended to keep the oil in, as there are 2 bushings in there, side by side, so oil would come out between them even when it was new under operating pressures. Does that cover plate go "outside" the bore and held in with the bushings? May be it's so worn it's falling into the bore? The online parts book shows nothing and the service book doesn't mention it either. I'm concerned even a new sleeve won't cure it, as it will leak around that too.

It's been to long since I have had one apart, but you do not have the right bushings in there, that much I am almost certain of that It should be a one piece bushing with a press fit. Let be double check the parts catalog just to make sure.

 

[Mike10]

It's been to long since I have had one apart, but you do not have the right bushings in there, that much I am almost certain of that It should be a one piece bushing with a press fit. Let be double check the parts catalog just to make sure.

Just checked the parts catalog and they call for only one bushing part number 9620426.

 

[PADeutzguy]

Just checked the parts catalog and they call for only one bushing part number 9620426.

Mike, I looked too... I see what you mean. Now I don't remember if there was an update to that or not. Now it seems like I do remember pushing out a big one and the local dealer saying use two, or he thought it was OK to use two. May be using two was the start of the wear and now it's done this damage. Another question since I'm studying this diagram... should oil even be back there?? Or is that just a dust cover? Why don't I see it in the online parts? I'm guessing it's not supposed to come out? Could the piston seals be completely shot and letting oil bypass it? With only 2 lines on the whole servo, may be nothing should be back there? Thanks so much for your help!!!

 

[Mike10]

Mike, I looked too... I see what you mean. Now I don't remember if there was an update to that or not. Now it seems like I do remember pushing out a big one and the local dealer saying use two, or he thought it was OK to use two. May be using two was the start of the wear and now it's done this damage. Another question since I'm studying this diagram... should oil even be back there?? Or is that just a dust cover? Why don't I see it in the online parts? I'm guessing it's not supposed to come out? Could the piston seals be completely shot and letting oil bypass it? With only 2 lines on the whole servo, may be nothing should be back there? Thanks so much for your help!!!

I believe oil is on both sides of the piston. The hole probably is used in the manufacturing of the housing and is plugged and not intended for it to come out. If you can get it back into place I would just get the right bushing and install it and see what happens. The right bushing will keep it from coming out. I was thinking but not sure that the servo oil pressure comes from the charge pump and not hydraulic oil pressure. If that is the case then you are talking low pressure at the servo. As I said it has been too long since I worked on one. You can probably run the lines down and determine which oil pressure is used.

 

[Mike10]

I believe oil is on both sides of the piston. The hole probably is used in the manufacturing of the housing and is plugged and not intended for it to come out. If you can get it back into place I would just get the right bushing and install it and see what happens. The right bushing will keep it from coming out. I was thinking but not sure that the servo oil pressure comes from the charge pump and not hydraulic oil pressure. If that is the case then you are talking low pressure at the servo. As I said it has been too long since I worked on one. You can probably run the lines down and determine which oil pressure is used.

Actually there is no charge pump but the charge pressure comes from a check valve back at the filters. Finally found a line drawing for the hydraulic system and charge pressure is what is used by the servos. The charge pressure check valve is set at 110 PSI so you are looking at low oil pressure to the servos.

 

[Mike10]

Actually there is no charge pump but the charge pressure comes from a check valve back at the filters. Finally found a line drawing for the hydraulic system and charge pressure is what is used by the servos. The charge pressure check valve is set at 110 PSI so you are looking at low oil pressure to the servos.

If you did the other servo the same way I would get those bushing out of there and install the right one or you may face this same problem again.

 

[PADeutzguy]

Actually there is no charge pump but the charge pressure comes from a check valve back at the filters. Finally found a line drawing for the hydraulic system and charge pressure is what is used by the servos. The charge pressure check valve is set at 110 PSI so you are looking at low oil pressure to the servos.

Right, otherwise when I took the seat out and moved the handle I didn't get a huge blast of oil, under full pressure I would have been soaked (I kept back from it, I know that high pressure oil can hurt you badly). I have to go to Lancaster PA tomorrow, and will be going near 3 NH dealers. May be one of them will have the parts on the shelf and I can stop and grab them. I really need this machine, I have 5 tons of wheat seed and 4 tons of fertilizer coming along with 2 semi loads of chicken manure for this one farm, and it's there broken down! I'm probably going to put a seal kit in it since it's apart. Dad thinks he rebuilt them about 10 years ago, so it's probably time again. If this doesn't fix it, I'll send it to the hydraulic machine shop, I'm sure he can fix it, it's just does he want to. They have so much work from the well drillers and frackers us little guys/farmers don't seem to matter anymore. 5 years ago we were his bread and butter, today they kinda roll their eyes at us when we walk in the door. Plus his prices have tripled! We would have bought a new machine 7-8 years ago, but we can't find any we like, the way this one feels and is balanced, none seem to compare today. It's been here so long it's like a member of the family now, it will probably be here forever. The new machines seem to run so fast and are so jerky, or are too big or too small. I guess since I cut my teeth on this machine nothing feels more natural to me, and nothing ever will. Same with my old 977's and 955 loaders, I feel like I'm on a wild animal with the "new" rear engine loaders. I've gotten used to them, but I think I can run a 977 in my sleep.

 

[Mike10]

Right, otherwise when I took the seat out and moved the handle I didn't get a huge blast of oil, under full pressure I would have been soaked (I kept back from it, I know that high pressure oil can hurt you badly). I have to go to Lancaster PA tomorrow, and will be going near 3 NH dealers. May be one of them will have the parts on the shelf and I can stop and grab them. I really need this machine, I have 5 tons of wheat seed and 4 tons of fertilizer coming along with 2 semi loads of chicken manure for this one farm, and it's there broken down! I'm probably going to put a seal kit in it since it's apart. Dad thinks he rebuilt them about 10 years ago, so it's probably time again. If this doesn't fix it, I'll send it to the hydraulic machine shop, I'm sure he can fix it, it's just does he want to. They have so much work from the well drillers and frackers us little guys/farmers don't seem to matter anymore. 5 years ago we were his bread and butter, today they kinda roll their eyes at us when we walk in the door. Plus his prices have tripled! We would have bought a new machine 7-8 years ago, but we can't find any we like, the way this one feels and is balanced, none seem to compare today. It's been here so long it's like a member of the family now, it will probably be here forever. The new machines seem to run so fast and are so jerky, or are too big or too small. I guess since I cut my teeth on this machine nothing feels more natural to me, and nothing ever will. Same with my old 977's and 955 loaders, I feel like I'm on a wild animal with the "new" rear engine loaders. I've gotten used to them, but I think I can run a 977 in my sleep.

If they do not have the right bushing I have already used a bushing from a New Holland 450 or 451 mower knife, I can't remember which but it did work. I had to do something to get it to work. I think I had to come up with a bushing to install in the knife bushing since the hole in the knife bushing is 1/2". I am thinking it was 11555 but not certain. If you have a helpful dealer I am sure they can come up with something to reduce the bushing hole size.

 

[PADeutzguy]

If they do not have the right bushing I have already used a bushing from a New Holland 450 or 451 mower knife, I can't remember which but it did work. I had to do something to get it to work. I think I had to come up with a bushing to install in the knife bushing since the hole in the knife bushing is 1/2". I am thinking it was 11555 but not certain. If you have a helpful dealer I am sure they can come up with something to reduce the bushing hole size.

Talked with the dealer on Monday, he suggested we drill out the hole where the plug/plate was and tap it to 3/8' and put a flat plug in it. It worked. We did this by removing the piston and rod, drilled it out, being very careful to be square, tapped it, installed the plug (Advance Auto parts had one) and used a die grinder to grind back where the bearing goes in. Hoping it's going to last a long time. Thanks for all your help.