1965 David Brown 880UE Implematic, how to prime transmission hydraulic pump?

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aczlan
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Location: NY, USA

Re: 1965 David Brown 880UE Implematic, how to prime transmission hydraulic pump?

Post by aczlan » Mon Jan 20, 2020 4:58 am

Gard wrote:
Mon Jan 20, 2020 3:17 am
As stated earlier I also wonder what was the original fault that someone disassembled it (and then put together wrong).
Me too.
Gard wrote:
Mon Jan 20, 2020 3:17 am
I do not know what inspection measurements are for the gears and bushings.
There are none listed to check when taking the pump apart in the 880 Implematic service manual that I have been using, this is the early pump with orings at the end of the bushes, so no end clearances to check like with the later pumps
Gard wrote:
Mon Jan 20, 2020 3:17 am
One thing in the schematic drawing above is the left one of the 3 way valves that feeds the lift cylinder is actually the middle valve on the tractor (at least on mine).
That is what the operators manual that I have I have says as well. When I had the valvebank apart, the valves has seemed a little gummed up, so I took the whole valvebank completely off of the tractor to rule out that being an issue.
Gard wrote:
Mon Jan 20, 2020 3:17 am
I am pretty sure the valves D and E above the pump need to be in the lower position in order to get high pressure flow to the lift. So make sure nut at 1 is loose above the lever and perhaps tap it down lightly. I think good flow to gear box lubrication imply one of these valves is lifted up a little or leaking, allowing flow out left of pump and to the lubrication circuit.
When I move the linkage so that the nut above valves D and E is down and loose, flow stops completely. When I move the linkage so that the nut is pulled up, flow starts again.
As such, I dont think that valves D and E are leaking by. Unless I am missing something, the only thing I see that could cause this issue is the non-return valve sticking closed and not letting fluid leave the pump unless you lift valves D and E.
Gard wrote:
Mon Jan 20, 2020 3:17 am
I remember seeing detailed instructions on how to make all the adjustments in the proper order, but not sure where that was. I doubt you can complete the procedure with a seized cable.
The cable is stiff, but it can be moved. I moved it to match what the diagram showed for a disconnected cable and followed the directions.
Gard wrote:
Mon Jan 20, 2020 3:17 am
Are you working in an area above freezing temperature, there may be a bit of water in the system someplace?
Above freezing? No, its been below freezing. I doubt that there is any water in there though, I have drained it and refilled it several times in the course of this adventure (including once when I had the transmission cover off and I sprayed the inside of the transmission down with diesel from a pump sprayer to make sure the crud was all cleaned out, I removed 15 gallons of sludge that was about the color and consistency of caramel yogurt from the transmission case when I started this project) and it has been sitting in the shop since, so it has not had a chance to have any water run into it.

Aaron Z

Gard
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Re: 1965 David Brown 880UE Implematic, how to prime transmission hydraulic pump?

Post by Gard » Mon Jan 20, 2020 1:47 pm

I think what you are seeing is consistent with a pump that is unable to put out enough pressure to overcome the spring on the non return valve shown at 4 in origional diagram or O in second diagram. If I understand correctly you only get flow in the blue path when both valves are raised. Another less likely possibility may be a stuck open pressure relief valve?

I guess if you had an issue with the TCU valve you would see oil squirting from the disassembled 3 way valve by feet instead of inches. I think even with a TCU valve that is open there will be hundreds of psi of back pressure at the 3 way, you would not want to try to stop it with thumb pressure.

It sounds like the pump parts appeared to be in good condition. My pump is a slightly different design but I think the bottom bushings need to be able to slide somewhat freely in the bottom of the bore in the pump body. When I assembled mine, I could see the top bushing was slightly above the pump body, held up by the O-Ring and compressed by tightening the cover. Not sure if yours is the same. From a practical standpoint if its a pressure compensated pump but something is sticky or worn, not enough pressure builds up to move the bottom bushing to seal. I am afraid I can not help much in debugging the pump further. Other than make sure all valves and components are cleaned again and all parts are present when reassembled,

aczlan
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Re: 1965 David Brown 880UE Implematic, how to prime transmission hydraulic pump?

Post by aczlan » Mon Jan 20, 2020 11:50 pm

Gard wrote:
Mon Jan 20, 2020 1:47 pm
I think what you are seeing is consistent with a pump that is unable to put out enough pressure to overcome the spring on the non return valve shown at 4 in origional diagram or O in second diagram. If I understand correctly you only get flow in the blue path when both valves are raised. Another less likely possibility may be a stuck open pressure relief valve?
Correct, I only get flow on the blue path when the valves are raised, when they are lowered, I get no flow from the pipe that feeds the 3 way valve, or from the lines that lubricate the transmission gears. If it was a stuck open pressure relief valve, I would think that I would always have some flow through the blue path when they were closed.
Gard wrote:
Mon Jan 20, 2020 1:47 pm
I guess if you had an issue with the TCU valve you would see oil squirting from the disassembled 3 way valve by feet instead of inches. I think even with a TCU valve that is open there will be hundreds of psi of back pressure at the 3 way, you would not want to try to stop it with thumb pressure.
I agree.
Gard wrote:
Mon Jan 20, 2020 1:47 pm
It sounds like the pump parts appeared to be in good condition. My pump is a slightly different design but I think the bottom bushings need to be able to slide somewhat freely in the bottom of the bore in the pump body. When I assembled mine, I could see the top bushing was slightly above the pump body, held up by the O-Ring and compressed by tightening the cover. Not sure if yours is the same. From a practical standpoint if its a pressure compensated pump but something is sticky or worn, not enough pressure builds up to move the bottom bushing to seal. I am afraid I can not help much in debugging the pump further. Other than make sure all valves and components are cleaned again and all parts are present when reassembled,
It is a standard gear pump, not a pressure compensated variable displacement pump, so it should pump fluid as long as it is rotating in the right direction and it does not have a suction leak or blockage.

Aaron Z

Gard
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Re: 1965 David Brown 880UE Implematic, how to prime transmission hydraulic pump?

Post by Gard » Tue Jan 21, 2020 5:46 pm

I agree it is not a variable displacement pump but based on the description in the manual copied below, I still think the bottom bush needs to be free to move in pump bore. Also I think the bushes need to be thick enough so the O-ring is compressed and sealed when the cover is bolted in place. If the bush is not pressed tight against the rotor by the differential fluid pressure I think the pump will not develop any pressure.
It is a little surprising to me there is no wear limit for bushing length in the manual
If you end up back inside there again I suggest removing the pump and also disassembling and cleaning the non return and pressure relief valves as well as the control valves if not done already.
The pump I recently had apart was a slightly different design so not sure if this applies but I ended up machining some metal off the pump body to account for bushing wear.
Where are you in NY? I was visiting Poughkeepsie last weekend
Attachments
imp pump theory.PNG
imp pump theory.PNG (113.21 KiB) Viewed 1552 times
imp pump dwg (Small).PNG
imp pump dwg (Small).PNG (143.95 KiB) Viewed 1552 times

aczlan
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Re: 1965 David Brown 880UE Implematic, how to prime transmission hydraulic pump?

Post by aczlan » Wed Jan 22, 2020 1:41 am

Gard wrote:
Tue Jan 21, 2020 5:46 pm
I agree it is not a variable displacement pump but based on the description in the manual copied below, I still think the bottom bush needs to be free to move in pump bore. Also I think the bushes need to be thick enough so the O-ring is compressed and sealed when the cover is bolted in place. If the bush is not pressed tight against the rotor by the differential fluid pressure I think the pump will not develop any pressure.
The orings do hold the bushes tight, it sat out about 1/32" before I started working around tightening bolts.
Gard wrote:
Tue Jan 21, 2020 5:46 pm
It is a little surprising to me there is no wear limit for bushing length in the manual
If you end up back inside there again I suggest removing the pump and also disassembling and cleaning the non return and pressure relief valves as well as the control valves if not done already.
Control valves were cleaned (there is a wear limit listed for those), I took the non-return valve out and I think I cleaned it, but that is my target tomorrow after work.
Gard wrote:
Tue Jan 21, 2020 5:46 pm
The pump I recently had apart was a slightly different design so not sure if this applies but I ended up machining some metal off the pump body to account for bushing wear.
If its not the non-return valve, its going to get the pump housing nut tightened all the way up (so its always bypassing) and I will rig up a way to connect a separate external line to drive the 3 point hitch (I will be putting a 3 spool valve to run off of the loader valve's power beyond and one of the spools is single acting).
Gard wrote:
Tue Jan 21, 2020 5:46 pm
Where are you in NY? I was visiting Poughkeepsie last weekend
Fingerlakes region, kind of between (and South of) Rochester and Syracuse.

Aaron Z

Gard
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Re: 1965 David Brown 880UE Implematic, how to prime transmission hydraulic pump?

Post by Gard » Thu Jan 23, 2020 9:47 pm

Its an interesting mystery to me as to what is not working in there. I know I would have a hard time giving up on the original system but I do not have any one tractor that I really need on the farm. I can understand the need to get it working one way or another (external pump) but its kind of a shame to loose other features like TCU. I wonder what it would take to test the pump outside the tractor to measure pressure and perhaps flow, perhaps there is a local hydraulic shop that could do it. Best of luck to you.

aczlan
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Re: 1965 David Brown 880UE Implematic, how to prime transmission hydraulic pump?

Post by aczlan » Thu Jan 23, 2020 10:02 pm

Gard wrote:
Thu Jan 23, 2020 9:47 pm
Its an interesting mystery to me as to what is not working in there. I know I would have a hard time giving up on the original system but I do not have any one tractor that I really need on the farm. I can understand the need to get it working one way or another (external pump) but its kind of a shame to loose other features like TCU. I wonder what it would take to test the pump outside the tractor to measure pressure and perhaps flow, perhaps there is a local hydraulic shop that could do it. Best of luck to you.
Took the PTO housing off, the non-return valve is free, not bound up at all. Re-adjusted the linkages (while I could easily get at everything), might have been a little tight (pulling up on the pump housing nut too soon). Going to pull the valve off of the top of the pump, verify that the hold and main relief valves didn't get swapped by the previous owner and put everything back together.

Aaron Z

aczlan
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Re: 1965 David Brown 880UE Implematic, how to prime transmission hydraulic pump?

Post by aczlan » Fri Jan 24, 2020 6:35 pm

One quick question before this all goes back together. I have the pump control valve off and on the bench, here is are a couple pictures of it:
PumpControlValve1.jpg
PumpControlValve1.jpg (88.53 KiB) Viewed 1470 times
PumpControlValve2.jpg
PumpControlValve2.jpg (135.4 KiB) Viewed 1470 times
Am I correct in thinking that the pointed valve is the "Main Relief" valve (F in the screenshot below) and the flat bottom valve is the "Hold Valve" (E in the screenshot below)?
PumpSchematicB.png
PumpSchematicB.png (156.48 KiB) Viewed 1470 times
It looks like I (or the previous owner) may have had the discs that the valves seat into backwards as (looking closely), there is a slight difference in the chamfer on the edge of the center hole, but otherwise I dont see anything out of place.

Aaron Z

Gard
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Re: 1965 David Brown 880UE Implematic, how to prime transmission hydraulic pump?

Post by Gard » Fri Jan 24, 2020 10:33 pm

I think you are correct about which valve is which, If you have not done so already, I suggest disassemble and cleaning of each, there are some small passages in them if I remember correctly.

aczlan
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Re: 1965 David Brown 880UE Implematic, how to prime transmission hydraulic pump?

Post by aczlan » Sat Jan 25, 2020 12:04 am

Gard wrote:
Fri Jan 24, 2020 10:33 pm
I think you are correct about which valve is which, If you have not done so already, I suggest disassemble and cleaning of each, there are some small passages in them if I remember correctly.
I had cleaned them one of the times I had things apart. Took them apart again to make sure, then put it back together, started it up and it works.
3 point goes up and down. Adjusting the TCU knob on the right side seems to change the lifting power (loosen it and the mower I had on the back would sink, tighten it and it would raise it.
The problem I ran into was that there was little or no "dead zone" between "Raise" and "Lower", it was either raising or lowering (unless I got the TCU knob dialed just right, then it would sit, but I couldn't raise it).
What do I need to adjust to increase the "Dead Zone" between "Raise" and "Lower"?

Also, it was warmish (35-40F), so I tried starting it with out plugging it in, it wouldn't start (cranked for 2-3 minutes). I popped a 1500W heat gun into the intake and turned it on. It went from not popping at all to running after about 2 seconds of cranking. Given how well that went, I will be adding a thermostart to replace the ether injector.

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db2d
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Re: 1965 David Brown 880UE Implematic, how to prime transmission hydraulic pump?

Post by db2d » Sat Jan 25, 2020 8:24 am

Briefly- with the cable that fits onto the top link disconnected the TCU does not come into play.
With the cable connected there is no hold position.
If the TCU pressure is adjustable with the cable disconnected there is something wrong either with the cable or the linkages in the control box. The lever connected to the control shaft inside the box maybe secured in the wrong position in relation to the hand control lever.
With the cable disconnected all control of the system is obtained by the movement of the small plunger that is situated under the control lever on the outside of the control box. This gives Lift- Hold and Drop operation.
Do you have a proper manual for the system? If not PM me your email address.

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cobbadog
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Re: 1965 David Brown 880UE Implematic, how to prime transmission hydraulic pump?

Post by cobbadog » Sat Jan 25, 2020 10:48 am

Glad you are getting closer to it working as designed. To my fading eyes when I look at the 2 valves E & F they look very similar with both having points at the bottom and that maybe the seat that the F valve sealed against has stuck to the bottom of that same valve. I know this is wrong but is what I first saw.

aczlan
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Re: 1965 David Brown 880UE Implematic, how to prime transmission hydraulic pump?

Post by aczlan » Sat Jan 25, 2020 12:51 pm

db2d wrote:
Sat Jan 25, 2020 8:24 am
Briefly- with the cable that fits onto the top link disconnected the TCU does not come into play.
With the cable connected there is no hold position.
If the TCU pressure is adjustable with the cable disconnected there is something wrong either with the cable or the linkages in the control box. The lever connected to the control shaft inside the box maybe secured in the wrong position in relation to the hand control lever.
With the cable disconnected all control of the system is obtained by the movement of the small plunger that is situated under the control lever on the outside of the control box. This gives Lift- Hold and Drop operation.
Do you have a proper manual for the system? If not PM me your email address.
I have a 880 user manual, but its for a Selectamatic. Just found one for the 950 Implimentatic last night (after I posted) which appears to have the same controls as the 880 and it answered some of my questions, if you have a better manual, my email address is my username at Gmail.
When disconnected, should the TCU cable be extended or retracted? Mine will move, but it is stiff and IIRC, it is currently fully retracted. I dont have a toplink that it will work with, so I dont plan on using it (and most of the use that the tractor will see will be moving round bales of hay, one on front, one on back).

Thanks

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ollek
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Re: 1965 David Brown 880UE Implematic, how to prime transmission hydraulic pump?

Post by ollek » Sat Jan 25, 2020 12:53 pm

The seat can not lift off the the pump body as the seat is locked in betwen the pump body and the valve body. If now the valve stricks to the seat, then the oil from the pump has no other way to go, than to push the non return valve open. The oil is now in the piping going to the lift cylinder and to the tcu valve via a t-piece in the piping. For a full pressure to the lift cylinder, the tcu valve must be closed.

aczlan
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Re: 1965 David Brown 880UE Implematic, how to prime transmission hydraulic pump?

Post by aczlan » Sat Jan 25, 2020 12:56 pm

cobbadog wrote:
Sat Jan 25, 2020 10:48 am
Glad you are getting closer to it working as designed. To my fading eyes when I look at the 2 valves E & F they look very similar with both having points at the bottom and that maybe the seat that the F valve sealed against has stuck to the bottom of that same valve. I know this is wrong but is what I first saw.
The only difference I can see (in the manual) is that one has a longer slot for the arm pulled up by the pump control nut to work in.
One of the ones installed in my tractor looks completely different from what's in the manual. I ended up deciding that since they have a common space on top and bottom that they flow into, I would make sure the seats matched the valves and call it good.
The pump control nut comes up freely (when assembled or disassembled), so I dont think that either was binding or sticking.

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