Symptoms 644E showing 500psi on the output of the brake/pilot pump, book shows set to 2000 psi, pump is a constant pressure, variable volume piston pump. Pump is used on it looks like a lot of the Deere 544/644 machines and this model belongs on a G series, but its on an E series, so okay, fine with that, likely its an overhauled pump or something.
Well, we open it up and the top cover is scored, maybe having a .001 groove where you'd normally have what's called a 'valve plate' on a typical swash plate type pump, there's even an index hole for a valve plate but none shown on the diagram, its part of the cylinder assembly. The cylinder is showing some wear and there's a piece of a flat slippery bearing hanging around the top of the pump where it does not belong.
Send the pump off to the local hydraulics rebuilder, verdict, pump is junk it cannot be fixed, suggest a reman for $1700, well JD wants $2005 for a brand new one. hmm. Now, we're not machinists or heavy equip specialists, I worked at an auto garage in high school and a few years after and love a challenge! Mostly we're gun enthusiasts and volunteer at the sportsmens club maintaining equipment. Anyway, we get the pump back in 1500 pieces, hmmm, well I'm really not sure how it goes back together. Some pieces are obvious so let me guess, the pump makes sense, the volume controller is a bit more difficult. This looks pretty close!
Now the pump, the floaty bit at the top was a bearing that sits around the base of the cylinder and keeps it aligned in the bore, there's a steel ring with a composite overlay bonded to it, it had become no longer bonded and was mostly a strip of slippery material on some type of metallic backing plate. One small piece of this ring was found in the bottom of the hydraulic tank later. This failed bearing was allowing the rotating barrel to **** sideways and unseal from the valve plate, causing the irregular scoring. Also, under the swashplate are two plain bearings, they look like half a connecting rod bearing that the trunion walks back and forth on as the swash plate pivots. In the bag of parts were two, one possibly made of plastic, Delrin would be my guess and the other is steel with a plastic composite overlay. Half of the overlay was mangled and missing. More bits found in the main suction screen. I measured the overlay thickness, 0.025, same as the thickness of the other bearing that was all delaminated. I peeled off the damaged overlay, cleaned the bearing shell with 400 grit paper, cut a piece from the cylinder bearing insert, soaked it in acetone and degreased it, then superglued it to the steel bearing shell, clamping it around a right sized socket wrench with a hose clamp and vice. Dried overnight and trimmed up in the morning, it looks fantastic! A little grinder work to file it to size and that's good to go.
I set to work lapping the end cap of the pump, it had a groove that was somewhere around half a thousandths deep, not big but might as well get rid of it. I brought in a cast iron surface plate, cleaned and dusted with spray glue, toss down a sheet of 180 wet/dry paper and a few drops of motor oil, too thick, changed over to light oil and lapped in a figure 8 pattern, 20 laps, turn quarter turn, keep going, check every 80 strokes. After a few passes it was sticking firmly to the paper, keep cleaning and changing the oil until the shadow of the scoring just barely disappeared.
Just a shadow of scoring remains at the 9:00 position but its damned near a polished surface. There are a few blotches, maybe some rust stains? They aren't in a critical area anyway, the letters down below are a reflection of a paint pail.
The cylinder valve area was not flat, it had a touch of a rounded profile to it, now as to the edges, maybe 001 out of flatness, I would have thought this piece was hardened but well, it felt pretty soft, just a few minutes of lapping on the 180 paper and it was almost hitting 100% of the surface, so changed over to 400 to polish and flatten it up as best we can. I was tempted to hold it by the top but knew that would lead to rocking so I held it right at the bottom, fingers got some lapping too.
So after a good cleaning, well I thought I cleaned it well, running a torch tip cleaner through the tiny little passages that supply oil to all the important parts, there is a hole in the swashplate, easily overlooked, it takes the smallest torch tip cleaner size and feeds oil to the composite bearing side under high pressure.
I oiled and put the pistons in, put the bearings and snap rings in, shaft, swash plate, tucked the top cover carefully in place. On the regulator, I backed the only adjustment bolt all the way out, hoping this was the final pressure setting, its not covered in the book. Put the regulator on the pump and capped the outlet port, poured some oil in the case drain and we pondered how to test.
One of my associates, Kevin came up with an awesome idea, 'How about we chuck it in the lathe!' Awesome! a piece of 1/2 copper pipe coupling to protect the 5/8 spline and mash the jaws down on it tight, a couple wood blocks on the ways and a c clamp to hold the pump down to the blocking, keeping the torque in check. Added a pressure gauge and valve and cobbled the whole thing up, what an awwesome mess!!
We used the inching function to spin the lathe over slowly, 50 rpm first setting, the pump spun, we put the case drain and pump outlet into the funnel and let it run for a bit, some small debris came out and we were using a strainer filter that caught all the little bits. At 100 rpm we were able to close the outlet and all the fluid came out the case drain, We ran it like this for a few minutes until the fluid flow cleared up. We weren't seeing more than 200 psi though, Duh! the pressure screw is backed all the way out, reach around the back and with a couple turns, 250, 400, 500, 800, 1000 pounds, let it run a while longer like this and we thought, the engine turns 800 rpm so we upped the speed to 600 and well, the pump proved to be too much toque draw for a 1.5 hp motor. We ended up backing off the rpm to around 550 and then keeping the main valve opened to a trickle, turning the pressure up to the required 2000!! Awesome. Also the 500 psi pressure from earlier had a lot of noise and vibration, now the gauge is steady as a rock even when you open the main valve, lathe starts to complain like all hell but the pressure stays spot on and the case drain flow is actually pretty low, maybe 1/2 gpm or so, it seemed less at the higher rpm's
So, a 'junk, non repairable' pump, Maybe half an hour of cleaning off the surface plate, an hour of careful lapping, $175 in bearings and seals from JD and we now have a brake/pilot pump that will put out full capacity. Why would the shop buck this? Maybe they don't have the skill to put sandpaper to steel? My bet is that its just not their bag, they'll clean and replace parts but where the parts are hard to get, just pull the plug and aim the customer at another pump.
Anyway, with the pump done, we pulled the machine back together, put in the center pins and called it a day!!
Well, we open it up and the top cover is scored, maybe having a .001 groove where you'd normally have what's called a 'valve plate' on a typical swash plate type pump, there's even an index hole for a valve plate but none shown on the diagram, its part of the cylinder assembly. The cylinder is showing some wear and there's a piece of a flat slippery bearing hanging around the top of the pump where it does not belong.
Send the pump off to the local hydraulics rebuilder, verdict, pump is junk it cannot be fixed, suggest a reman for $1700, well JD wants $2005 for a brand new one. hmm. Now, we're not machinists or heavy equip specialists, I worked at an auto garage in high school and a few years after and love a challenge! Mostly we're gun enthusiasts and volunteer at the sportsmens club maintaining equipment. Anyway, we get the pump back in 1500 pieces, hmmm, well I'm really not sure how it goes back together. Some pieces are obvious so let me guess, the pump makes sense, the volume controller is a bit more difficult. This looks pretty close!
Now the pump, the floaty bit at the top was a bearing that sits around the base of the cylinder and keeps it aligned in the bore, there's a steel ring with a composite overlay bonded to it, it had become no longer bonded and was mostly a strip of slippery material on some type of metallic backing plate. One small piece of this ring was found in the bottom of the hydraulic tank later. This failed bearing was allowing the rotating barrel to **** sideways and unseal from the valve plate, causing the irregular scoring. Also, under the swashplate are two plain bearings, they look like half a connecting rod bearing that the trunion walks back and forth on as the swash plate pivots. In the bag of parts were two, one possibly made of plastic, Delrin would be my guess and the other is steel with a plastic composite overlay. Half of the overlay was mangled and missing. More bits found in the main suction screen. I measured the overlay thickness, 0.025, same as the thickness of the other bearing that was all delaminated. I peeled off the damaged overlay, cleaned the bearing shell with 400 grit paper, cut a piece from the cylinder bearing insert, soaked it in acetone and degreased it, then superglued it to the steel bearing shell, clamping it around a right sized socket wrench with a hose clamp and vice. Dried overnight and trimmed up in the morning, it looks fantastic! A little grinder work to file it to size and that's good to go.
I set to work lapping the end cap of the pump, it had a groove that was somewhere around half a thousandths deep, not big but might as well get rid of it. I brought in a cast iron surface plate, cleaned and dusted with spray glue, toss down a sheet of 180 wet/dry paper and a few drops of motor oil, too thick, changed over to light oil and lapped in a figure 8 pattern, 20 laps, turn quarter turn, keep going, check every 80 strokes. After a few passes it was sticking firmly to the paper, keep cleaning and changing the oil until the shadow of the scoring just barely disappeared.
Just a shadow of scoring remains at the 9:00 position but its damned near a polished surface. There are a few blotches, maybe some rust stains? They aren't in a critical area anyway, the letters down below are a reflection of a paint pail.
The cylinder valve area was not flat, it had a touch of a rounded profile to it, now as to the edges, maybe 001 out of flatness, I would have thought this piece was hardened but well, it felt pretty soft, just a few minutes of lapping on the 180 paper and it was almost hitting 100% of the surface, so changed over to 400 to polish and flatten it up as best we can. I was tempted to hold it by the top but knew that would lead to rocking so I held it right at the bottom, fingers got some lapping too.
So after a good cleaning, well I thought I cleaned it well, running a torch tip cleaner through the tiny little passages that supply oil to all the important parts, there is a hole in the swashplate, easily overlooked, it takes the smallest torch tip cleaner size and feeds oil to the composite bearing side under high pressure.
I oiled and put the pistons in, put the bearings and snap rings in, shaft, swash plate, tucked the top cover carefully in place. On the regulator, I backed the only adjustment bolt all the way out, hoping this was the final pressure setting, its not covered in the book. Put the regulator on the pump and capped the outlet port, poured some oil in the case drain and we pondered how to test.
One of my associates, Kevin came up with an awesome idea, 'How about we chuck it in the lathe!' Awesome! a piece of 1/2 copper pipe coupling to protect the 5/8 spline and mash the jaws down on it tight, a couple wood blocks on the ways and a c clamp to hold the pump down to the blocking, keeping the torque in check. Added a pressure gauge and valve and cobbled the whole thing up, what an awwesome mess!!
We used the inching function to spin the lathe over slowly, 50 rpm first setting, the pump spun, we put the case drain and pump outlet into the funnel and let it run for a bit, some small debris came out and we were using a strainer filter that caught all the little bits. At 100 rpm we were able to close the outlet and all the fluid came out the case drain, We ran it like this for a few minutes until the fluid flow cleared up. We weren't seeing more than 200 psi though, Duh! the pressure screw is backed all the way out, reach around the back and with a couple turns, 250, 400, 500, 800, 1000 pounds, let it run a while longer like this and we thought, the engine turns 800 rpm so we upped the speed to 600 and well, the pump proved to be too much toque draw for a 1.5 hp motor. We ended up backing off the rpm to around 550 and then keeping the main valve opened to a trickle, turning the pressure up to the required 2000!! Awesome. Also the 500 psi pressure from earlier had a lot of noise and vibration, now the gauge is steady as a rock even when you open the main valve, lathe starts to complain like all hell but the pressure stays spot on and the case drain flow is actually pretty low, maybe 1/2 gpm or so, it seemed less at the higher rpm's
So, a 'junk, non repairable' pump, Maybe half an hour of cleaning off the surface plate, an hour of careful lapping, $175 in bearings and seals from JD and we now have a brake/pilot pump that will put out full capacity. Why would the shop buck this? Maybe they don't have the skill to put sandpaper to steel? My bet is that its just not their bag, they'll clean and replace parts but where the parts are hard to get, just pull the plug and aim the customer at another pump.
Anyway, with the pump done, we pulled the machine back together, put in the center pins and called it a day!!
Hydraulic pump win!! in shop rebuild success
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